French polishing is a method of applying finish to wood by hand with a cotton pad. In the guitar world the term "French polish" is understood to be a shellac spirit varnish that has been applied by the French polishing method. Most of the fine old musical instruments made in Europe were French polished, as are a majority of fine classical guitars being hand made today. It is a most highly-prized and desired finish for both its visual and tone enhancing characteristics. The luster, texture and color of the wood are all noticeably enhanced under an expertly applied French polish finish. The cured shellac film is also very thin and flexible and is believed to produce the clearest and most natural sound from the vibrating wood of the guitar, especially the top plate.
Achieving a professional quality French polish finish is highly dependent on the practiced skill and experience of the finisher. Although the method is very labor intensive and time consuming, most finishers seem to receive enough personal satisfaction from the resulting finish to warrant the effort. The application method is very simple with minimal material and equipment requirements. The only materials required are shellac, alcohol, lubricating oil, fine pumice, and a special polishing pad. This polishing pad is made of a small wad of cotton or wool wrapped tightly inside a linen cloth that is held firmly in the palm of the hand during polishing. This polishing pad, lightly charged with the shellac solution, is wiped (“padded”) in a continuous motion over the wood surface with each pass leaving a very, very thin layer of shellac over the last. Multiple polishing sessions are required over many days or weeks to achieve the best results. The French polishing method will be explained in more detail in a following section.
The recipes for shellac spirit varnish are many, but the most basic formula is shellac (Lac button or flake) dissolved in denatured alcohol solvent. Some other recipes may contain small amounts of common gums or resins intended to improve the resulting film in some slight way, but most finishers use the basic shellac/alcohol solution. The finish dries to the touch almost immediately because of the fast evaporating alcohol solvent but it takes weeks or months for it to fully cure.
The advantages of using French polish as a guitar finish are related to both the finish and the process. The beauty of the wood under this finish is undisputed, and it is generally regarded as the best finish for tone. Even with these accolades for the finish, the actual process, French polishing, has benefits for the maker. It is very “organic”, very personal and tactile. The finisher can watch the surface closely as he works and can minutely adjust material and method as the finish slowly builds and improves through multiple polishing sessions. This direct connection to and control of the results will certainly appeal to many craftsman. There is no equipment required, the materials are few and inexpensive, and the finishing can be done in a very limited space. The vapor and material are not hazardous or toxic, no need for air ventilation or face mask. This finish can easily be repaired or refreshed at any time. Additionally, shellac is used as a sealer or initial wash coat under any finish.
Although this list of advantages seems to make this the overwhelming choice for any instrument or situation, here are some drawbacks to consider. Even though a French polish finish is thin and flexible (good for sound) it is not very protective against even minor physical abuse. It will dent, scratch, or wear away in situations that would not affect the much harder lacquer finishes. This padded shellac finish is protective enough for classical guitars that are usually handled very carefully but not at all suited to instruments that may be handled more casually like electric or steel string guitars. To achieve an acceptable finish by French polishing requires the development of skills that are entirely new and different to most woodworkers. This works against the success of the novice builder when finishing his first instruments. The overall time and intense hand work required for French polishing limits its use in the smaller shops with higher production as well. In both of these cases spraying or brushing of some lacquer product may be more appropriate.
LMI provides all the necessary materials for French Polishing together in the Finish section. You will find three grades of shellac flakes available - blonde (pale), amber, darker amber. Some builders prefer some degree of amber shade in the finish and one of these three grades will suit their needs. Also offered in this section are denatured alcohol solvent (FPDENAL), pumice for filling/leveling (FPPUM), and rottenstone (FPROT) and felt pads (FPFELT) for rubbing out the finish. The pad lubricating oil (olive oil, paraffin oil, or mineral oil) and the cotton or linen cloth to make the pad are readily available in markets and thrift stores.
THE FRENCH POLISHING PROCESS
There are only a few simple elements required for French polishing wood surfaces:
- An appropriate cotton pad to apply the shellac
- The shellac solution ready to be applied to the pad as it is needed
- Alcohol added to the pad to either thin or to polish the shellac during padding
- A fine oil occasionally added to the pad to lubricate its movement during polishing
- Pumice for filling or leveling the surface, as needed (Optional technique)
In preparation for learning the French polishing technique, then, we will start with thorough directions for making the cotton application pads, for preparing the shellac solution, and guidelines for using the alcohol, oil, and pumice during the French polishing process. After these physical elements are described, we will move forward with a detailed description of the use of the pad to build a French polished shellac finish.
As these elements are more thoroughly understood and practiced by the finisher the easier and simpler the French polishing process will become.
INTRODUCTION TO THE POLISHING PAD AND POLISHING MATERIALS
The details of the French polishing process - its techniques and materials - actually vary slightly from craftsman to craftsman, culture to culture - different types of pads, shellac solutions, techniques, finishing schedules - but the basic elements are the same for them all.
Application Pad -Essentially the shellac application pad is a cotton or wool ball wrapped in a piece of tighter weave cotton and held in the palm of the hand. A French polish finisher will normally work with two different size pads - the majority of the padding is done with a larger, palm-size pad for the open, flat surfaces, and a smaller pad held by fingertips to polish smaller areas and tight corners. These pads are made in a variety of sizes and shapes and are called by many names - mouse, rubber, tampon, muneca - but we will refer to the French polishing application pad as the pad, or the polishing pad.
A polishing pad is made up of two parts - the internal wadding, or filler, and the outer cover cloth.The internal wadding is used to give the pad its shape and firmness. It also serves to absorb and hold the shellac, alcohol, and oil applied to the pad during French polishing. Small amounts of the polishing liquids are held in the wadding and minute amounts of the shellac solution are pushed out to the pad cover cloth and deposited on the wood surface during the action of polishing. The most common wadding materials are cotton waste material, 100% lamb’s wool (available as a Dr. Scholl’s product in drugstores), and cotton cheese cloth or gauze. The size, shape, and firmness of the application pad can easily be adjusted by changing the size and shape of the wadding.The wadding is wrapped and held tightly in one or two sheets of cotton cloth. This cover cloth is usually linen or lint-free, tight weave cotton material. The most common source of this material is old, high quality sheets or pillow cases - washed countless times. The smoother the surface of this cover cloth cotton is the smoother that the padded shellac surface can be.So, our French polishing pad is just another finish application tool, like a brush or spray gun. More thorough directions and guidelines for developing this padding technique are detailed in the next section.
Make a Pad - A good size pad is about the size of a compressed golf ball. Of course the wadding is softer and more flexible but this is about the right size. Start by determining the size of wadding that will compress down to a golf ball size. Then place that ball of wadding into the middle of an 8” x 8” piece of cover cloth. Wrap the cover cloth around the wadding and hold the loose cloth ends together tightly in the palm of your hand. The cover cloth should be held tightly enough around the wadding that the pad becomes a semi-firm, flat ball. The pad is shaped and flattened out by pressed it into the palm of your other hand. This main pad is ready for use, and it will be used for the vast majority of the polishing. A smaller pad is made for polishing tight corners - around the edge of the fingerboard or bridge. This smaller pad should be about the size and shape of a fat finger with only a small amount of wadding used.
Prepare the Shellac solution -Shellac is available in many forms and grades. The best choice for French polishing is freshly made from high quality shellac flakes. Make shellac fresh for each project. We recommend the LMI Pale, blonde shellac flakes dissolved into solution with the LMI Denatured alcohol.
- A 1-pound cut shellac is 1 pound of shellac flake dissolved in 1 gallon of alcohol.
- A 2-pound cut is 2 pounds of shellac flakes per 1 gallon of alcohol - or 32 oz. (by wt.) of shellac flakes dissolved in 128 ounces (by vol.) of alcohol
- 2 oz. of shellac flake + 8 fluid ounces of alcohol = 8+ ounces of 2-pound cut shellac.
The French polishing shellac recipe outlined below will yield over eight (8) fluid ounces of 2-pound cut shellac - more than enough to finish one instrument.
Shellac Recipe - Pour 8 fluid ounces (240 ml) of LMI Denatured alcohol FPDENAL into a wide-mouth glass or plastic jar. Add 2 oz. (56 grams) of LMI Pale, blonde shellac flakes FPPLATINA8 to the alcohol in the mixing jar. The shellac flakes may dissolve easier and more thoroughly in the alcohol if they are crushed up into finer pieces. Put the lid on the jar and let the shellac dissolve for one or two days. This 2-pound cut may not dissolve entirely in one day, so stir or mix up the solution and let it dissolve a second day. Decant this solution into another container through a coffee filter to remove any lingering wax or impurities. This mixture will yield 8+ ounces of shellac solution. Put some of this shellac solution (2 to 4 ounces) into a smaller container to use during French polishing. Some of the remainder of this prepared shellac will be used first as a sealer over the raw wood at the beginning of the finishing process.
Use of Alcohol during French polishing -The denatured alcohol is the solvent for the French polishing shellac solution - the liquid in the solution is alcohol. A small amount of this alcohol is used from a small dispenser bottle during the actual padding process to thin the shellac in the pad as needed, usually in the final polishing sessions. As each padding session nears completion with an adequate finish build-up more alcohol than shellac is added to the pad - but never very much. The solvent action of even this small amount of alcohol on the pad smoothes and glosses the new surface and, more importantly, draws the lubricating oil out of the freshly padded shellac. This is sometimes referred to as “spiriting off”. This alcohol pad can also be used to help smooth out rough shellac surfaces. Never make the pad wet with alcohol. Too much alcohol in the pad can literally wipe the fresh shellac finish right off the surface. Just a couple of drops of alcohol occasionally on a dry, or drying, pad will work to “spirit off” the trace of oil left in the shellac from the polishing process.
Use of Oil during French polishing -The pad carries the shellac and distributes it onto the wood surface while padding, but the finish dries so quickly that the pad can easily stick to the freshly padded shellac surface and create a flaw in the fresh finish. A drop of fine, thin oil is periodically added to the pad surface to lubricate its movement over this building shellac layer. This mild lubrication is necessary for effective padding/polishing. Several types of oil can be used - fine mineral oil (baby oil), virgin olive oil, or paraffin oil - and they all work equally well in this application.
The oil is added to the pad during the polishing process. After fresh shellac is applied to the drying pad for more padding, a drop of oil is added to the polishing surface of the pad. This will lubricate the pad until more shellac is needed - maybe 2 to 4 minutes of polishing. If the pad becomes too dry, it will begin sticking to the surface while padding. Add oil to the pad surface and the pad will again move smoothly.
Be conservative with the oil. Avoid adding more than a drop or two of oil to the pad at any one time. When the pad is overloaded with oil it moves very easily over the surface and the surface looks glossy, but no shellac is actually being applied. Excess oil can be trapped in the shellac finish and leave it a little cloudy. Also, it takes time and effort to remove the oil residue from the polished shellac finish - so, if less oil is used in polishing, less oil will need to be removed by the “spiriting off” process.
Use of Pumice powder during French polishing - The ultra fine pumice powder is a mild abrasive - a commonly used ingredient in facial creams and soaps. During French polishing the fine pumice powder can also be used as a very mild abrasive to help diminish surface flaws in freshly applied shellac coats. This is an OPTIONAL technique, though, because it is not required during the normal course of the French polishing process outlined here.
Using the pumice powder, then, is actually a shellac REPAIR tool that can be used sparingly to help even out or smooth the rough shellac surface over damaged or repaired areas. While padding the repaired area normally with shellac, sprinkle a minute amount of pumice over the damaged area and continue padding. You will feel a slight abrasive action of the pad immediately - actually, the pad is grinding the surface slightly AND laying down a new fine shellac layer at the same time. This technique is not precise. Observe the effect of padding with the pumice and adjust the amount of pumice used to the amount of leveling action that is needed. The severity of the flaw or damage to the finish surface will determine how well this shellac finish may be blended back flat and smooth with this method. Of course, repeated cycles of sanding the area (w/600 or800) and more padding will bring any flawed finish surface back to a new, perfectly flat condition.
The pumice powder can be sprinkled on the surface, or it can be delivered to the surface with a cotton pounce bag. Some pumice powder is wrapped tightly in a small cotton cloth - just tapping this cotton “ball” on the polished surface will release a small amount of powder through the cotton weave to the polished surface.
In more traditional French polishing this pumice powder is also used to fill the pores in the hardwoods. To fill the pores, pumice powder is sprinkled on the raw wood surface and is padded aggressively into the pores with a pad that is wet with alcohol and very little shellac. Repeated additions of pumice with continuous padding - over several padding sessions - will fill the pores. This method is very time and labor intensive. The pore filling process we use here as part of our complete French polishing procedure is simpler and shorter. See the FILL OPEN PORES IN HARDWOOD section of the complete finishing process.
Comment on the use of these padding materials -Successful French polishing is partially determined by using correct, effective amounts of the shellac solution, the alcohol, the lubricating oil, or the OPTIONAL pumice powder as they are needed with the polishing pad.
When first learning to use these materials it is best to start by adding small amounts to get the feel or understand the effect slowly. Too little shellac or alcohol added to the pad will have no negative affect on the finish surface while polishing, but too much shellac or alcohol can be disastrous. Be conservative -- only use more shellac or alcohol in the pad as your experience and comfort with the padding process increases.
USING THE PAD TO APPLY SHELLAC / French polishing technique
With an understanding now of the polishing pad itself and the finishing materials used with it, we can begin describing how the pad is actually used to French polish the thin shellac finish onto a guitar. This use of a polishing pad to apply the shellac finish is the central technique of the French polishing process. In practice, the raw wood surfaces are sanded smooth, pore filled, and sealed first before the padding process begins, but we will describe the finish padding technique in detail now and refer to it later in the outline of the complete finishing schedule.
As we explained briefly before, the polishing pad is used to wipe or rub thin, consecutive layers of shellac onto the wood surface, building the final finish only through many of these padding sessions. By varying the amounts of shellac, alcohol and oil that are used during polishing, the polishing pad is used either to build up the finish layer, or to smooth out rough surfaces, or to polish the surface to a high gloss.
Each major surface area -the top, back, sides, and neck - will require at least four to six complete polishing sessions applied over a 10 to 14 day period to build up an adequate finish over the entire instrument.
French polishing - one padding session, step by step - This entire sequence will later be referred to as a “polishing session” or “padding session”. This padding session will be repeated many times during the complete French polishing of one guitar.
- Prepare for the polishing session by laying out polishing pads (stored in an airtight container) and the shellac solution, alcohol, and oil in small dispenser bottles - all within easy reach of the polishing area. Wear eye protection and thin surgical gloves.
- Position good light sources so that the polishing area is well illuminated. It is necessary to be able to see the polished surface very clearly during the polishing process. The reflection of the light source off the finish will reveal minute changes in the surface of the developing finish layer.
- With the instrument ready on the work surface begin the polishing session by gripping the application pad firmly in the palm of the polishing hand and gathering the cover cloth tightly around the wadding ball with the fingertips. Press the pad flat against the palm of the opposite hand to form a wider, flatter polishing surface.
- Hold the pad with the polishing surface up and add a small amount of shellac solution (a few drops) directly to the polishing surface of the pad. This is called “charging” the pad. Also add a drop of oil to the pad surface for lubrication.
- Quickly tamp or press this “charged” pad into the palm of the opposite hand several times. This action is believed to form a flatter padding surface and to distribute the finishing liquids more evenly throughout the internal wadding of the pad.
- With light pressure the pad is rubbed over the wood surface in a continuous circular motion. Move the circulating polishing pad back and forth slowly, and methodically, over the area being finished. Each swirl of the pad should leave a barely visible, minute amount of shellac on the surface.
- Concentrate the French polishing in a limited working area - ¼ of the top, ¼ of the back, or ½ of a side - and polish that area thoroughly before moving to finish more area.
- The pad must be in motion as it contacts the surface. The pad must be in continuous motion while polishing the surface. The pad must be in motion as it is lifted from the polished surface. If the motion of the pad is slowed down or stopped on the freshly padded surface it will stick and damage the fresh finish. Then extra padding, filling, and time will be needed to repair the area. With a little practice, though, you learn to start the padding motion in the air just above the surface and smoothly drop the moving pad onto the surface continuing the circular polishing motion.
- As the pad dries out with a few minutes of polishing increase the pressure of the pad to the surface. This pressure will push the last of the shellac to the surface of the pad and then onto the wood. At some point it will be obvious that no more shellac is being applied to the surface and the dry pad is beginning to stick. Move the pad off of the surface.
- “Charge” the pad with more shellac solution. Add a drop of oil to the pad surface.
- Continue padding the shellac methodically, and evenly, over the same working area.
- “Charge” the pad with more shellac solution every few minutes as the pad dries out.
- Close observation of the finish surface during padding will show the finish develop as the very thin shellac passes slowly build into a noticeable finish layer. This finish build-up may be uneven, though, so concentrate more padding over the thin finish areas to build a shellac layer of relatively even thickness over the entire working area.
- Work the pad in smaller or larger circles, as needed, moving the polishing pad slowly and methodically over the entire working area.
- When a noticeable finish layer has been built up over this entire working area, “charge” the pad with a few drops of alcohol (no shellac solution) and polish over the surface in larger circles. Add more alcohol drops to the pad and continue polishing. This action will remove some of the oil from the surface and give a more accurate view of the surface of the fresh finish layer. This closer look at the finish surface will most likely reveal that the finish is thinner and less evenly applied than it appeared before.
- “Charge” the pad with more shellac, add a drop of oil to the pad surface.
- Continue padding more shellac over the working area, focusing on the areas where the shellac layer was thinner or uneven, and then build more finish over the whole area.
- With a good shellac layer now over the first working area, begin finishing the next area, and then the next.
- When each working area of the surface - back, top, sides, or neck - is thoroughly polished, work over that entire surface as a whole. Look closely over the whole surface and pad more shellac over any weak areas or transitions between working areas.
- Padding builds the finish layer very slowly. It may take 30 minutes or more of polishing, as well as “charging” the pad 15 to 20 times, to build an adequate shellac layer on the back - or sides - for example.
- When an adequate shellac layer is built up over the entire surface (of the back, or top, or sides, or neck) stop charging the pad with shellac.
- Add several drops of alcohol to the polishing pad and aggressively polish over the entire surface.
- As the pad dries out add more drops of alcohol and continue padding, smoothly and evenly, over the whole surface. Polish with a circular motion and finish by polishing in long, straight strokes with the grain. Smooth, even, and consistent polishing with this alcohol pad will diminish any minor surface imperfections -like the fine swirl marks left by the pad during shellac polishing.
- When the entire surface has been polished with the alcohol pad for a few minutes, the padding session is completed. This short “spiriting off” process at the end of each polishing session will remove some of the oil left from polishing and clean up the surface a bit.
Each polishing session will follow this same sequence, although the padding material is changed from straight shellac to straight alcohol slowly through successive polishing sessions. In the first 4 to 6 polishing sessions the straight 2# cut shellac is repeatedly added to the pad and polished onto the surface to build an adequate finish layer. These polishing sessions are the “building” stage of the French polishing process. When an adequate finish layer is finally built up, alcohol is added to the pad with the shellac solution for one or two polishing sessions. Finally, the surface is polished once or twice using only alcohol in the pad. This alcohol padding will gloss and smooth the shellac surface while removing the oil residue. This is the “spiriting off” stage of the process.
Now that the basic elements of the French polishing finishing method - the pad, the finishing materials, and the shellac padding technique - are better understood we will offer the complete finishing process that includes this French polishing technique to apply the shellac.
SUGGESTED FINISHING PRODUCTS:
- Pale, blonde shellac flakes FPPLATINA8 - 8 oz. for shellac padding and for sealing.
- Denatured alcohol, 1 qt. FPDENAL - solvent for shellac solution.
- LMI Pore Filler FMBF8 (choose the appropriate color) - used to fill the open pores of rosewood, mahogany, etc.
- TRI-M-ITE No-load Sandpapers FMTMT - 120/220/320/400 grits to final sand wood surfaces before finishing.
- WET-OR-Dry Polishing Papers FWOD - 600/1200/1500 grits for the very fine leveling of cured shellac between padding sessions.
- Pumice for filling and padding FPPUM
- Rottenstone for polishing FPROT
- Felt block, 5” x 5” x ¾”, FPFELT
- Liquid Polishing Compounds - Fine polish, FFP, Super fine FSP.
- Fine oil - baby oil/mineral oil, olive oil, paraffin oil - for lubricating the movement of the polishing pad.
COMPLETE FRENCH POLISHING PROCESS - DETAILED PROCEDURES
PREPARATION OF WOOD SURFACES BEFORE FINISHING
- All surfaces must be sanded smooth and scratch-free. On the hardwood sides, back, and neck, sand with the TRI-M-ITE no-load papers. Use progressively finer grit papers from 120 grit through 220 grit - sanding with the direction of the grain. To maintain flat surfaces always use sanding blocks or rubber sanding pads to support the paper. Use progressively finer grit sandpapers to remove the scratches from the previous sanding.
- Check for course sanding scratches that may have been missed by the final fine sanding. Closely and carefully examine the surface for any scratches or flaws. This close examination of the surface (and your sanding progress) can be enhanced by wiping the surface with Naphtha or lighter fluid and closely examining the surface while it is wet with fluid. While wet the sanded surface will appear as it will under finish and even small scratches will be apparent.
- Re-sand with the finer grit sandpapers to remove any scratches or flaws found by this close examination.
- Repeat this sanding process on the softwood top, but you may need to proceed through the finer 320 grit paper for a perfectly smooth, scratch-free surface.
- Totally remove the sanding dust from all surfaces with compressed air and/or wiping the surface with a rag or paper towel wet with Naphtha or lighter fluid. Some finishers will wipe these surfaces with a cloth damp with water to raise the grain, then repeat the final sanding and cleaning. There are probably as many finishers that don’t do this step as there are that do. Use your own discretion
- Mask off the fingerboard . The instrument is ready for finishing.
INITIAL SHELLAC SEALER COATS
With all of the surfaces prepared and cleaned for finishing, the next step is to seal the entire instrument with a wash coat of shellac. This thin sealing coat will form a barrier coat on the wood surface and in the pores that will make the pore filling process easier and will keep the pore filler from staining the raw wood surface.
- Prepare the shellac solution for padding and sealing. We will prepare 8 ounces of 2 pound cut shellac - enough for all padding and sealing. See the Prepare the Shellac solution section for the recipe details. Put 4 ounces of the shellac solution into a smaller container to use during French polishing. The remaining 2 ounces of this shellac will be used to make the shellac sealing solution.
- Prepare shellac sealing solution. Add 4 ounces of Denatured alcohol to the 4 ounces of 2 # cut shellac solution. This will make 8 ounces of a thinner, 1 # cut shellac solution for sealing the raw wood before and after the filling process.
- Use a pad or brush to apply a coat of the shellac sealing solution over the entire instrument. Seal the top first, while the pad or brush is fresh and clean - then seal the neck, back and sides. Don’t brush or pad back and forth over the rosewood - the dark color will be picked up and moved around the surface. Apply the shellac onto the surface in one direction and with minimal overlapping of the brush or pad strokes.
- Let this thin sealing coat dry for at least an hour before proceeding.
- Very lightly sand the raised grain roughness from all surfaces with 320 grit paper backed by a flexible block or pad. Be careful to sand very lightly and not sand through this thin material - just barely remove the surface roughness. Use fresh paper often at this stage.
FILL OPEN PORES IN HARDWOOD
Most of the hardwoods used for guitar bodies and necks - e.g. all rosewoods, Koa, Walnut, Mahogany, and more - have very open pore structure. These open pores show as a multitude of tiny depressions throughout the smoothly sanded surface of these hardwoods. It is essential to fill these tiny depressions to achieve a flat and smooth surface. This is the most important step in the finishing process to achieving a perfect glass smooth final finish. Committing the time and keen attention toward filling the pores effectively, and thoroughly, at this stage will reduce the time and effort used to build up a smooth, pore-free finish later.
By contrast, Maple, Sycamore, and the Spruce and Cedar top woods, are non-porous and sand smoothly enough that this filling process is not required. The shellac can be padded directly onto these non-porous woods when the thin shellac sealer coat is dry.
We recommend filling the pores with our easy-to-use, water-based LMI Pore Filler, FMBF8. This material is an excellent, fast drying filler that produces a smooth flat surface on porous woods. This product is available in three shades - light Natural/Maple color, Reddish-brown Mahogany, and Dark Walnut/Rosewood. Select the color that best matches your wood.
LMI Pore Filler dries hard within a few minutes, so this water-based paste must be applied to the wood surface in an entirely different manner than the traditional oil-based filler is applied. The wet, creamy, water-based filler paste is simply squeegeed across the wood surface - and into the pores - with a flexible plastic card or palette knife. With this fast drying pore filler an instrument can be pore filled, thoroughly, then re-sealed with shellac and be ready for French polishing within a few hours.
- Thin the LMI Pore Filler, FMBF8, about 20% (4 parts of paste to 1 part water). This will make the paste wet, creamy and easy to work with. Any time that the paste dries out it can be made more creamy or liquid by adding small amounts of water and mixing it into the paste. Always work with wet, fresh filler paste when filling the pores.
- Work in small areas - maybe 3” X 3” or 4” X 4” - and closely observe the progress of the pore filling as you thoroughly work that small area.
- Fill the pores with filler paste. With the flexible plastic squeegee or artist’s palette knife spread a small amount of wet filler paste over the wood surface.
- Immediately scrape this wet filler off of the surface with the plastic squeegee or palette knife. This will leave wet filler in the pores and small depressions. Work the wet paste filler over the surface and into the pores and scrape it off several times in the next minute or so. Scrape as much filler off of the surface as possible and stop scraping before the filler begins to dry (within minutes).
- As you finish this pore filling process in one area just continue by spreading and working fresh filler paste over new areas. You should be able to pore fill the entire back in this manner in 10 to 15 minutes - the same time for the sides.
- Leave the filler to dry in the pores for a minimum of one (1) hour before proceeding. With more drying time the filler is marginally harder. It is hard enough to sand after one hour of drying.
- Remove any filler residue from the wood surface by sanding the entire surface lightly with 220 grit no-load paper. Some or all of the shellac sealer may also be sanded off at this point. That’s OK, just don’t sand down through the filled pores.
- Seal the wood and filled pores again with shellac. Pad or brush one good coat over the newly filled surfaces. Let this coat dry at least an hour before proceeding.
- REPEAT the entire pore filling process just completed. This second pore filling will fill any tiny pores or depressions missed the first time. You may want to thin the paste even a little more for this second filling. Work the wet paste over the surface quickly, efficiently, leaving wet filler paste only in open pores and leaving very little paste residue on the wood surface. This can best be achieved by scraping the plastic squeegee or palette knife all directions across the surface. You can get very effective at this filling process with a little practice. When this second coat of paste filler has dried (about 1 hour) sand the surface smooth again with 220 grit paper. When the sandpaper clogs replace it with fresh paper. The surface now should be very smooth, pore free, and scratch free.
- Seal the filled hardwood surfaces again with shellac. Let this coat dry at least on hour before proceeding.
- Examine all wood surfaces very carefully. If you find any scratches under the sealed finish sand them out now with 220 grit paper. Apply sealer back over any sanded surface.
- The instrument is now ready for beginning the French polishing process.
BUILDING THE SHELLAC FINISH BY FRENCH POLISHING
Building a sufficient shellac finish layer that is also very flat with an even thickness over the entire surface area is more difficult to accomplish with a pad than it is with spraying or brushing. With spraying and brushing either lacquer or varnish a thick layer is built up with multiple applications. Then this thick finish layer is sanded and buffed down to a thinner flat and smooth final surface.
The process of building French polished shellac finish is different, though. The shellac layer builds up very gradually over many polishing sessions with each swirl of the polishing pad leaving only a miniscule amount of shellac. So, when padding shellac the idea is to build the finish layer up to the final thickness through many polishing sessions. This developing finish layer is leveled lightly several times during the shellac building process by minimal wet sanding with very fine sandpaper, making the final polished surface flat and smooth.
With all of the previous work on the guitar - fine sanding, sealing, pore filling, re-sealing - each surface has been made as flat, smooth, and pore-free as possible before beginning to French polish the shellac. Even with all of this preparation, though, there will still be a few small areas that are not 100% filled on each surface. So, the focus during padding is to apply more shellac over these areas, while applying a relatively even coat over the whole surface.
There will be as many as 4 to 6 French polishing sessions needed over each surface - top, back, sides, neck - to build up an adequate final finish. It is difficult to polish more than one surface at a time, though, because the freshly padded shellac is slow to harden and will mark for a while after padding. So it may be beneficial to polish a whole surface, let it set and dry for a couple of hours, then manipulate the guitar into position and polish the next surface once the finish has hardened a bit.
The following French polishing process outline will cover the steps to completely build and polish the shellac finish on one major surface. It is understood, though, that the same procedures and sequence are used to completely finish each surface of the guitar. See the FURTHER COMMENTS AND PROCESS ALTERNATIVES section at the end for some tips on polishing the different areas of the guitar.
The terms “polishing session”, “polishing pad “,” padding“, “Building stage”, “spiriting off”, and “charging the pad“ will be used throughout the French polishing process outline. Please refer to previous sections for detailed and thorough descriptions for each of these techniques or processes.
First polishing session -
- Begin the first polishing session over the pore-filled and sealed guitar surface.
- Follow the directions and guidelines in the French polishing - one padding session, step by step section to French polish a layer of shellac over the entire surface.
- This first polishing session will only form a very thin shellac layer over the wood. It may not appear much thicker than a shiny gloss on the raw wood.
- Allow this first, very thin shellac coat to cure for at least two days.
Second polishing session -
- Begin the second polishing session directly over this cured first layer, as it is. DO NOT sand or level this thin finish in any way at this time.
- The shellac being padded over this cured initial coat will build up a more substantial layer easier than during the first polishing session over sealed raw wood.
- Recharge the pad often with shellac and continue padding until a good layer of shellac covers the entire surface being worked.
- Do not be concerned about minor flaws or irregularities or swirl marks as they appear on the finish surface, just continue padding to build a substantial shellac layer.
- Carefully “spirit off” the entire surface to remove some of the oil remaining on the surface and in the shellac from the padding process.
- Allow this more substantial freshly padded layer of shellac to cure at least two days before working on this surface again.
Level the shellac layer by wet sanding -The shellac padding process can build a good finish layer but as more and more shellac is applied by hand the finish surface eventually shows the affect of uneven padding, or swirl marks from the padding, or dust or lint in the finish. After this new coat is cured it can be leveled flat by sanding before more shellac is padded on. The building shellac layer must be leveled several times during the finishing process to assure that the final finish is as flat and smooth is possible.
Shellac is much thinner and softer than cured lacquer or varnish, though, and it sands very fast by comparison. So, the wet sanding of the shellac finish is done with very fine sandpaper with only light pressure. We will sand/level the shellac with either 600 grit WET-OR-DRY sandpaper between padding sessions or with 1200 grit WET-OR-DRY sandpaper before the final polishing.
- Prepare the sandpaper and sanding pads. Cut or tear the 600 grit sandpaper sheets into smaller 2 3/4" X 4 1/4" pieces to use with the sanding pad. Also, make a 2" X 2 3/4" rubber or Styrofoam sanding pad to back the sandpaper during wet sanding. Using a sanding pad is necessary to establish and maintain a flat finish surface while sanding.
- The lubricating fluid used for wet sanding the shellac is mineral spirits. Put several ounces of mineral spirits (paint thinner/turpentine) into a squeeze or spray bottle for easy dispensing during sanding. The mineral spirits in the dispenser bottle can be made into a slightly more effective sanding lubricant by adding a few drops of light oil to it.
- This first shellac coat is very thin and relatively flat. The objective of this wet sanding session is to sand very lightly and only level the minor padding flaws or uneven areas on the surface. This is NOT an aggressive leveling - only level the high points on the thin shellac surface and remove or diminish any minor padding flaws or other imperfections on the finish surface.
- Wet sand the surface. Wrap one of the small sheets of 600 grit sandpaper around the sanding pad and apply some mineral spirits to the instrument surface - pour a few drops and smear it around. Slide the sanding pad over the wetted area with light pressure. Use fresh sandpaper as the used ones clog up. After wet sanding the entire surface lightly, stop sanding and wipe the surface clean with a paper towel.
- With good lighting examine the sanding result very closely. Examine the entire surface and identify any areas where swirl marks, or minor surface flaws still exist.
- Focus a little more wet sanding over the areas with surface flaws.
- Wipe the entire surface clean - this surface is ready for the next polishing session.
At this point the shellac layer is still very thin but is beginning to form into a flat, smooth sheet of shellac. This is a good start but several more shellac polishing sessions will be needed to build up the desired final finish. So, the goal of these next few shellac polishing sessions is to build the shellac layer up closer to the final thickness. This will be the “building” stage of the process.
Observe the finish surface closely during the polishing process. Focus your attention and more padding on filling any remaining pores or gaps in the rosette or binding, and on building up any thin areas to keep the finish uniform throughout.
A flat, smooth and pore-free finish is eventually achieved through these successive sessions of padding the shellac to build the finish and wet sanding to maintain a level surface.
Third polishing session -
- Build a fresh shellac layer by the process outlined earlier in French polishing - one padding session, step by step.
- Focus the shellac polishing on filling any open pores and building up any thin areas.
- Build a good, even shellac coat over the whole surface.
- Lightly “spirit off” the excess oil from the surface.
- Allow at least two days for this coat to cure before proceeding.
Level the shellac layer by wet sanding -
- Follow the earlier instructions for wet sanding and lightly level the surface with 600 grit paper.
- Again -- only sand lightly to level any high points on the shellac surface. Remove or diminish any minor padding flaws or other imperfections on the finish surface, and level the areas with extra finish built up to fill open pores.
Fourth polishing session -
- Build another shellac layer - follow steps listed above in the Third polishing session.
- Allow at least two days for this coat to cure before proceeding.
Level the shellac by wet sanding - (OPTIONAL wet sanding session)
- Examine the surface of the finish very closely.
- Do not proceed with wet sanding if there are no noticeable minor flaws, pad marks, open pores or uneven areas in the surface.
- Proceed with a mild wet sanding with 600 grit paper over any imperfections that may be found on the surface.
Fifth polishing session -
- Carefully and methodically build another coat of shellac by French polishing as before.
- This may be the final polishing session of the shellac “building” stage.
- Be especially attentive to completely fill any lingering open pores and to build up any thin finish areas at this time.
- At the end of this polishing session the finish should finally be built up to a perceivable depth (thickness) over the whole surface.
- Allow this fresh shellac finish to cure for at least three (3) days. This 3-day curing period will insure that it is hard enough for a more aggressive wet sanding session.
Level the shellac THOROUGHLY by wet sanding at this time -
- With the shellac finish finally built up to a sufficient thickness, and cured hard, it should now be leveled more thoroughly than during the previous wet sanding sessions.
- First, wet sand with the 600 grit sandpaper and mineral spirits as before. Level every area of the surface to create a flat and smooth surface throughout. Sand out any last pores in the surface that received extra padding in the last polishing session.
- This sanding is only slightly more aggressive than the previous light sanding sessions.
- REMEMBER - Even this thicker shellac will sand away fast, so be careful not to over sand any one area and risk sanding through the finish to the wood.
- When every area has been sanded and is dull with very fine sanding scratches stop sanding with the 600 grit sandpaper.
- Now, wet sand over this area again with 1200 grit sandpaper and mineral spirits.
- Sanding with the much finer 1200 grit sandpaper will diminish or remove the 600 grit sanding scratches from the surface, making it even smoother.
- The surface is now ready for the final polishing sessions.
Since the finish is now built up to its final thickness the next polishing session will not be used to build up more finish. We will be padding with a thinner shellac solution (more alcohol) to put a thin final glossy shellac layer over the sanded surface. And last, we will polish the surface with only a little alcohol in the pad. This will have the affect of smoothing and glossing the final surface.
Final shellac polishing session -
- Begin this session by putting a fresh, clean cover cloth on the polishing pad. This is necessary for building the very smooth, flaw-free final finish surface.
- “Charge” the polishing pad with a few drops of shellac solution and a few drops of alcohol.
- This thinner shellac solution will not build up as quickly as the thicker shellac (2 # cut) used during the “building” stage.
- Polish over the area methodically and watch the surface closely as the very thin shellac slowly builds and diminishes the fine scratches left from the wet sanding.
- As the fine scratches disappear and a thin, smooth, glossy coat is developed over an area, stop building more finish there and move the polishing to an adjacent area.
- When the entire surface is padded well with this thin, smooth and shiny coating, stop polishing with the shellac.
- Now polish over the entire surface with only alcohol added to the pad.
- Apply only a few drops of alcohol as needed to the polishing pad and polish vigorously over the entire fresh shellac surface. This polishing will further smooth out and gloss this final finish.
This polishing session should produce the final, smooth, flat and flaw-free finish. Closely examine the whole surface. If there are still any minor flaws or uneven areas in the surface, let it cure for a day, then lightly wet sand the area with 1200 grit sandpaper and polish again with this thinner shellac solution.
SPIRIT OFF THE FINAL FINISH - When the final finish is achieved through all of these polishing sessions let the finish cure for two days. There will still be some of the lubricating oil coming to the surface. The finish will be slightly cloudy and the oil can be felt on the surface. This oil should be “spirited off” the shellac layer by one or two more polishing sessions using only alcohol in the pad.
- “Charge” the polishing pad with a few drops of alcohol and begin polishing the surface.
- As the pad dries out add more drops of alcohol and continue polishing, smoothly and evenly, over the whole surface. Polish mostly with a circular motion but finish by polishing with long, straight strokes with the grain.
- Polishing with alcohol at this stage should create a very flat and smooth glossy surface.
- Let this finish set for a day and “spirit off” again if needed.
POLISH THE CURED FINISH TO A HIGH GLOSS
Many finishers are satisfied with the shellac finish as it appears now after the final sessions of polishing with alcohol. With skill and good fortune a very acceptable finish is produced “off the pad” with no further polishing or buffing needed. You will have to examine the finish surface and make this judgment for yourself.
If an even finer finish is desired an even smoother and higher gloss can be achieved by polishing the surface with the traditional Rottenstone and oil solution. To polish the surface effectively the finish must be thoroughly cured - for at least seven days or more.
- There may be very minor imperfections or unevenness in this cured surface - such as very minor orange peel surface from the final polishing with alcohol.
- Wet sand lightly with the 1200 grit sandpaper and mineral spirits as a lubricant to make this surface smoother before polishing.
Traditional gloss polishing-
- Cut a smaller a 2” x 2” felt piece from the 5” x5” x ¾” Felt block FPFELT. This will be the polishing pad.
- Pour a few drops of the lubricating oil on the finely sanded finish, then sprinkle some of the powdered Rottenstone FPROT over the same area. Lightly mix the two into solution with your fingers. The solution should be more oil than powder so that the very thin paste will remain liquid for easy polishing.
- With the small pad felt polish the surface with this oil and rottenstone solution.
- Primarily use a circular polishing motion moving the rotating polishing pad slowly over the surface many times. Add oil or rottenstone as required to keep this polishing solution liquid and effective.
- As the working area becomes glossy finish up with straight stokes with the pad.
- Polish one small working area at a time and occasionally wipe the surface clean so that the results of the polishing can be closely observed.
- As each smaller area is glossed to perfection move on to polish other areas.
- When all of the smaller working areas are glossed work the surface as a whole to create a uniform look over the entire surface.
- Be patient. Work the entire surface until you are satisfied that the surface gloss or texture is as good as it can get before stopping.
Let the instrument set for several days for the finish to thoroughly harden before it is handled. The instrument finishing is completed.
FURTHER COMMENTS AND PROCESS ALTERNATIVES
The complete French polishing process as outlined here will take 15 to 20 days to complete - plus the final curing time before handling. This is a moderate time scale. There are schools of French polishing where the finish is applied much quicker, providing only a very thin final finish and delivering the instrument in less than one week. There are also polishers that take months to complete a perfect finish. This process - with 2 to 3 day curing times - will produce a good finish with lacquer-like depth and look in the safest time frame.
This very labor and skill intensive finishing method relies heavily on the observation and judgment of the finisher as the finishing progresses. It does not yield easily to set formulas. The number of polishing sessions required can differ from those listed here- as there are different conditions, woods, and skills with each case. The key to successful polishing will be the eventual understanding of the different materials and elements involved and adapting the technique and materials used to the changing conditions of the developing finish. Experience with the different elements will improve the process greatly.
Although conditions for success at each stage are tenuous for the beginner and mistakes can happen, this building finish is very malleable and repairable - even in mid process. Mistakes or flaws can usually be corrected by more padding and sanding at any stage.
Some guitar makers prefer a lightly colored finish, usually shades of amber. These shaded finishes can be created by using the darker shellacs - Medium amber FPYELLOW8 and Dark amber FPAMBER8 - for some of the building coats. Once the right color is achieved complete the finishing with the Pale blonde shellac.
The different surfaces of the guitar require different padding styles or pads. the whole back, most of the top and sides are polished easiest with the larger polishing pad. The tight corners and small areas of the neck and head, the fingerboard/top intersection, and the sides/neck heel intersection will require the use of the smaller pad and/or just a polishing cloth held in the fingers to sufficiently coat all areas.
- Many finishers prefer ethyl alcohol (Everclear) over the denatured alcohol recommended here.
- 800 grit and 1000 grit papers may be very effective in sanding the shellac during the building and polishing stages. Even various grits of Micromesh FMIC are preferred by some finishers for some of the sanding.
- The very final finish surface may also be polished/buffed to a high gloss using our lacquer polishing liquids, Fine polish FFP or Super fine FSP.
- Many of the more experienced French polishers may add various gums or resins to their shellac varnish recipe to enhance or improve a particular characteristic of the finish. We will leave these specific shellac recipes for consideration later when the novice finisher has enough experience with the simple shellac recipe.