Solvent-based Nitrocellulose lacquer has been the dominant finish used by U.S. musical instrument factories for steel string guitars, arch top guitars, banjos and mandolins since the 1920’s. It would not be an exaggeration to say that all, or nearly all, vintage/collectable American factory steel string instruments are finished in lacquer. (Until very recently solvent-based nitrocellulose lacquer was simply referred to as “lacquer” in the musical instrument business.)
This finishing material is made of nitrocellulose combined with other resins (to promote flexibility, durability, etc.) dissolved in lacquer thinner solvent. The lacquer film forms and cures as the solvent evaporates. Lacquer thinner is a volatile, “hot”, solvent containing a combination of hydrocarbon and chemical solvents - including naphtha, xylene, toluene, acetone, various ketones, and others. This strong solvent base is lacquer’s best advantage and primary disadvantage.
Lacquer thinner solvent is strong enough to dissolve subsequent coatings together, and it can easily dissolve a cured lacquer finish as well. This feature makes the finishing process and any touch-up or repair easier and more controllable compared to other finishing systems (with the possible exception of the KTM9 waterbased finish). Solvent-based lacquer has been so extensively used in the guitar and furniture industries that all of its application and cured film properties are very well known and available. The resulting cured lacquer film is excellent for musical instruments. It is hard and durable, yet flexible, and can easily be buffed to a beautiful high gloss when cured. This finishing system is also well supported with a full spectrum of pigments and dyes for coloring, as well as abundant pore filling, sealing, spraying, sanding and buffing products.
Although nitrocellulose lacquer can be applied by brush (with the addition of retarder ), it is best applied, as intended, with proper spray equipment and some kind of ventilation hood or booth.
The main drawback of lacquer thinner solvent based finishing is the hazardous nature of the evaporating solvent itself. Intermittent exposure to the lacquer thinner vapors is a potential health risk, so it is necessary to wear a vapor mask, and to avoid skin and eye contact as well, when working with lacquer or lacquer thinner. Strong ventilation of the spray mist while spraying, and of the curing instrument after spraying, is a must. While most guitar builders prepare for, or accept, the space, equipment and safety requirements needed to spray lacquer effectively, there is a small but growing number of amateurs and professionals working to eliminate hazardous and toxic materials from their homes and shops. For these builders solvent-based lacquer is problematic.
LMI supplies Lawrence McFadden™ solvent-based lacquer (our part FL128). This McFadden™ lacquer is the most widely used and respected nitrocellulose lacquer product line available for musical instrument finishing. This finish was specifically developed for guitar finishing and is now used by many high-end production and repair facilities. To complement the finish lacquer we offer McFadden’s matching sealer (FLSW) and lacquer retarder (FLRFT).
Other materials used with solvent-based lacquer:
- Staining raw wood - Use either our Alcohol Soluble Aniline Dyes, FSB or Water Soluble Aniline Dyes, FSBW or dye concentrate, FMDY (Water-Soluble or MEK-Soluble).
- Shading color mixed into finish - Use either our Alcohol Soluble Aniline Dyes, FSB or dye concentrate - MEK-Soluble, FMDYMEK.
- Sealer used under lacquer - Use our McFadden Vinyl Sealer, FLSW or Shellac/alcohol solution.
- Pore filler - Use either our McFadden's Pore Filler, FPF or LMI Micro-bead Acrylic Paste Filler, FMBF.
COMPLETE FINISHING PROCESS
Nitrocellulose lacquer has been used to finish musical instruments for decades. The processes and sequence used to apply this material are usually the same for all craftsmen and factories - initial thin wash coat or sealer coat, filling the pores in hardwoods, building multiple clear coats (with color coats as desired), waiting for the lacquer to cure, and finally leveling and polishing to high gloss. While these processes and finishing sequence are generally followed by most finishers, the details of the individual processes used in these factories or small shops can vary greatly - yet still yield the same highly desired thin, glass-like final finish on the completed instrument.
Rather than list and compare these variations to the entire process, we will outline - step by step - one specific process that will yield a very acceptable final finish, even for a first-time semi-skilled finisher. For most craftsmen finish application is not a fixed, static process anyway, but is rather an ever evolving, changing one. Small changes are often initiated in the finishing process to either improve the process itself or the finish.
Lacquer is usually applied by spraying, so the process outlined here will focus on this method of application. It should be noted, though, that the thin sealer used in the initial stages can be applied by brush as easily as sprayed, and that the clear lacquer can also be applied by brush successfully if it is slightly thinned (15-20%) with lacquer retarder. Lacquer retarder is a very slow thinner - it retards the drying process and allows the lacquer to flow out flat and smooth before drying hard. So the process outlined here can be used for brushing application as well as spraying.
The entire finishing process will first be displayed here as a simple outline, a useful lacquering schedule for experienced finishers. Second, there is a longer set of instructions with each step more fully detailed.
But even these more detailed instructions are not intended to teach the inexperienced every minute detail of the woodworking or finishing processes involved here. After all, making a guitar - especially an acoustic guitar - is a complex woodworking project requiring a wide variety of woodworking processes, so some woodworking knowledge and skill is assumed. When the directions say "spray the lacquer...", we assume that the craftsman has use of all of the required equipment - compressor, spray gun, ventilated spray booth/area, etc. - and that he has some familiarity, skill and experience in the use of this equipment in spraying finishes.
Safety precautions: Use a dust mask when sanding raw wood. Use a vapor mask and latex gloves when mixing and applying finishing materials. Wear eye protection at all times.
SUGGESTED FINISHING PRODUCTS:
- McFadden's Spray Lacquer FL128 - 1 gallon will finish 3+ guitars, 1 quart may not be enough for one guitar, especially for a novice finisher.
- McFadden's Vinyl Sealer FLSW32 - 1 quart is enough sealer for 2+ guitars.
- Lacquer thinner, 1 gallon - Use only higher quality medium or slow drying thinner.
- McFadden's Lacquer Retarder, 1 pint FLRFT- to improve flow-out, avoid "blushing".
- Pore filler - either McFadden's Pore Filler FPF (choose the appropriate color) or LMI Micro-Bead Paste Filler FMBF8 (choose the appropriate color).
- TRI-M-ITE No-load Sandpapers FMTMT - 120/220/320 grits to final sand wood surfaces before finishing.
- WET-OR-DRY Sandpapers - 220/320 grits for leveling lacquer build coats.
- WET-OR-Dry Polishing Papers FWOD - 600/1200/2000 grits for the very fine sanding of cured lacquer before polishing.
- Liquid Polishing Compounds - Cut polish FCP, Fine polish FFP, Super fine FSP.
LACQUER FINISHING PROCESS - SIMPLE OUTLINE
PREPARATION OF WOOD BEFORE FINISHING
- All surfaces must be sanded smooth and scratch-free - Sand to 220grit on hardwoods.
- Repeat this sanding process on the softwood top - Sand top to 320 grit.
- Totally remove the sanding dust from all surfaces.
- Mask off the fingerboard and cover the soundhole.
INITIAL VINYL SEALER WASH COATS
- Seal the entire instrument with a wash coat of thinned Vinyl Sealer FLSW32.
- Very lightly sand the raised grain roughness from all surfaces with 320 grit paper.
FILL OPEN PORES IN HARDWOODS
- Thin the pore filler, so that it is creamier and easier to apply.
- Apply the pore filler, use either McFadden's Pore Filler FPF or LMI's Micro-Bead Pore Filler FMBF8.
- Remove excess filler material from surface, leave pores filled.
- Seal the surfaces with a coat of Vinyl Sealer.
- Repeat the pore filling process. This second pore filling fill any pores missed by the first session.
- Re-seal the surfaces with a coat of Vinyl Sealer.
- Examine all sealed surfaces very closely for any sandpaper scratches. If scratches are found sand them out now and re-seal the wood.
BUILDING THE CLEAR LACQUER FINISH
- Mix a thin lacquer solution.
- Spray several coats of thinned clear lacquer to start the process.
- Mix the thicker Building lacquer solution.
- Spray four (4) coats of Building lacquer.
- Sand this coating level with 220 grit sandpaper.
- Spray four (4) more coats of Building lacquer.
- Sand this coating level with 320 grit paper.
- OPTIONAL - Spray another coating of Building lacquer over the back, sides, and neck - if pore depressions are still evident.
- Sand this third coating level with 320 grit paper.
- Mix the Final lacquer solution - slightly thinner solution with lacquer retarder.
- Spray four (4) coats of the thin Final lacquer.
ALLOW THE LACQUER TO FULLY CURE
- Guitar factories and small shops will let this lacquer cure anywhere from 4 to 14 days before buffing. We recommend the longer 10 to 14 day cure time for the best results.
FINE SAND THE CURED LACQUER SURFACE
- First sanding - Wet sand the entire instrument thoroughly with 600 grit paper
- Second sanding - Wet sand with 1200 grit paper, remove all 600 grit sanding marks.
- Third sanding - Wet sand with 2000 grit to further smooth the 1200 grit surface.
POLISH THE LACQUER TO A HIGH GLOSS
- Use our Fine Polishing Compound FFP and a cotton polishing pad to hand buff/polish the finely sanded semi-gloss surfaces up to a high gloss finish.
- Hand polish all surfaces again with Super Fine Polishing Compound FSP to achieve a glass-like ultra-high gloss.
LACQUER FINISHING PROCESS - DETAILED PROCEDURES
PREPARATION OF WOOD 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. Each progressively finer grit must remove the scratches from the previous sanding. Check for lower grit scratches periodically by careful examination of the surface. 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 wet with fluid. While wet it will appear as it will under finish and even small scratches will be apparent.
- 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 and cover the soundhole as required. The instrument is ready for finishing.
INITIAL VINYL SEALER WASH 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 thinned Vinyl Sealer FLSW32. This thin sealing coat will form a thin barrier on the wood surface and in the pores that will make the pore filling process easier and keep the pore filler from staining the raw wood surface. Equally important, this vinyl sealer increases the adhesion of the clear lacquer to the wood surfaces - and to plastic bindings. Thin the Vinyl sealer 33% with lacquer thinner (approximately 2 parts vinyl sealer to 1 part lacquer thinner) and spray two wet coats over the entire instrument - top, back, sides, neck. Let the first wet coat dry about an hour before the second coat is applied. This sealing coat will dry enough to proceed in an hour.
- Very lightly sand the raised grain roughness from all surfaces with 320 grit paper backed by a 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 in spraying and sanding the clear lacquer coats later in the process.
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 clear lacquer can be sprayed directly onto these non-porous woods when the thin vinyl sealer coat is dry.
We offer two different types of pore filler for use under solvent-based lacquer - McFadden's Pore Filler FPF, a traditional oil-based filler and LMI Micro-Bead Acrylic Paste Filler FMBF8, a newer water-based filler. Each of these pore fillers is available in several shades - from light natural color through dark brown (rosewood). Select the color of filler that best matches your wood.
Both types of pore filler are used extensively in guitar finishing currently, and each can produce a smooth, pore-free surface on porous hardwoods. The main differences between these two types of pore filler are the methods of application and the time required for each to dry thoroughly enough to move on to applying the clear lacquer coats. We will outline here the application methods for both types of pore filler and let the individual craftsman choose which method best fits his skills and experience.
Two different fillers and two methods to fill pores:
- Using Mc Fadden's Pore Filler, FPF - an oil-based filler
- Thin the McFadden's Pore Filler FPF about 20% (4 parts filler to 1 part mineral spirits). This makes the filler paste the consistency of thick latex paint and a little easier to work with a paint brush.
- Work in smaller, manageable areas - like one half of the back or one side at a time. As the filling and rubbing is completed in one section move on to pore fill the next area.
- Brush the thinned pore filler over the surface to be filled. Work the filler into the pores by brushing the still wet material back and forth across the grain. Remove the pore filler that collects on the brush and brush across the whole area at 45 degrees to the grain direction to remove all but a thin layer of filler. The intent here is to leave only a very thin coat of filler on the surface but to have all of the pores filled.
- Wait for the pore filler material to dry to a semi-hard paste - the glossy shine of the wet pore filler will turn dull when it is dry enough to wipe off. This should be about 15 to 20 minutes after the filler was brushed on.
- Wipe the excess pore filler off of the surface. With a hand full of rough cloth (burlap), or a course nylon pad (scuff pad), wipe the dry filler off of the surface of the instrument. Wipe only across the grain with the rough cloth or nylon pad to remove the semi-dry filler from the smooth surface of the wood. By wiping across the grain you will be able to remove the semi-dry filler from the flat surface without pulling the filler back out of the pores. Actually by rubbing hard across the grain with the course cloth or pad you'll be packing the semi-dry filler down into the pores. Use a clean portion of the wiping rag or pad for a final wiping of the surface. At this point almost all of the filler is removed from the surface and there is semi-dry filler packed into all of the pores. Set the instrument aside so that the filler can thoroughly dry and harden. There is a more detailed description of this filling process in Michael Dresdner’s book, The Woodfinishing Book - LMI item # BM27.
- Wait at least 24 hours for the oil-based filler to dry. Some finishers even suggest waiting 2 days for this type of filler to dry and harden completely.
- Sand the dried filler residue from the wood surface with 220 grit no-load paper. Sand with the grain and sand only enough to remove all dried filler residue from the surface. This sanding will remove most, or all, of the thin sealer coat is well, exposing raw wood again. Sand lightly and carefully - just barely remove the filler residue and the thin layer of sealer from the wood surface but don't sand through the filled pores.
- Seal the wood and filled pores (again) with a spayed coat of the thinned Vinyl Sealer - FLSW32. Spray one wet coat of vinyl sealer over the surfaces that were filled and sanded.
- REPEAT the pore filling process outlined above. Yes, fill the pores a second time. Invariably, there can still be scores of tiny depressions left on the surface - unfilled pores, partially filled pores, small gaps in joints - after only one pore filling session. This second pore filling session should fill the pores missed on the first session. Wait a day for the filler to dry again and carefully sand the thin filler residue off the entire surface. When you sand the dried filler residue off of the surfaces this time, examine the pores very closely. They should all be filled and level with the wood surface.
- Seal the wood and filled pores (a third time) with two wet coats of thinned vinyl sealer. Let the first wet coat dry about an hour before the second coat is applied. Let this second coat dry at least on hour before proceeding.
- The hardwood surfaces are pore filled and sealed, ready for the lacquer finish coats.
- Using LMI Micro-Bead Acrylic Paste Filler FMBF8 - a water-based filler
LMI Micro-Bead 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 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, and sealed (vinyl sealer) and ready for lacquer finish coats within one day.
- Thin the LMI Micro-Bead 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 but the sanding may go better with two or three hours wait.
- 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 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 the thinned Vinyl Sealer - FLSW32. Spray one wet 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 with two wet coats of thinned vinyl sealer. Let the first wet coat dry about an hour before the second coat is applied. Let this second 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. Shoot sealer back over any sanded surface.
- The instrument is now ready for the clear lacquer finish coats.
BUILDING THE CLEAR LACQUER FINISH
The process of building the final lacquer coating on the instrument follows this general sequence - first, a few initial thin coats to start building the lacquer, next, apply 4 coats of thicker lacquer as primary building coats, sand/level this coat, apply 4 more building coats, sand/level the surface, and finally, spray a couple of coats of lacquer with more lacquer retarder added to make the final coat lay out very flat and smooth.
The prime objective of this process is to build a lacquer film surface that is flat and smooth without any pore depressions. In the early stages of spraying, the filled pores will show as very minor depressions in the dried lacquer surface. With more building coats, though, and some careful wet sanding of the finish surface between coats, the resulting lacquer film will be flat, even, and smooth - and ready for polishing when it is completely cured.
Follow these steps for the spraying and sanding details.
- Spray the first thin lacquer coats
- Thin the McFadden’s Spray Lacquer FL128 about 50% with high quality medium or slow-drying lacquer thinner (1 part lacquer to 1 part lacquer thinner). This is a very thin solution and will leave only a thin lacquer film over the wood. You will need about a pint and a half of this 50/50 mixture. Adjust air pressure and lacquer feed at the spray gun for the best spray pattern with this thin solution.
- Spray two (2) thin coats of this 50/50 thinned lacquer over the entire instrument - top, back, sides , and neck. This is thin material so it will build up and drip easily without continuous movement of the spray gun over the instrument. This coat will dry to the touch in 20 to 30 minutes.
- Make a very thorough examination of this first clear lacquer coat. Look very closely for any scratches still left in the wood (there should be none at this stage) and lightly sand out any dust or specks in the finish with 320 grit WET-OR-DRY sandpaper with water as a lubricant.
- Spray another wet coat of this 50/50 thinned lacquer over the entire instrument.
- Let this thin, initial coat of lacquer dry for at least an hour or two before proceeding.
- Spray the first Building coats of clear lacquer
- Thin the McFadden’s Spray Lacquer FL128 about 25% with lacquer thinner (3 parts lacquer to 1 part thinner). Now add a small amount of Mc Fadden’s Lacquer Retarder (very slow thinner) FLRFT to the lacquer solution, enough to equal about 5% of the total solution. This is the lacquer recipe we will use for the “building” coats - the lacquer mixture is thick enough to build depth, but is thinned and retarded enough to flow out flat and smooth over the surface. Adjust your spray gun with more air pressure and adjust the nozzle tip for more fluid to get this thicker solution to spray good wet coats. Lightly wipe off all surfaces with a Tack Cloth FTC to remove any dust on the surface before spraying.
- Spray two (2) wet coats of this building lacquer over the entire instrument. Spray with even, overlapping coats in one direction (e.g. up and down) over each surface. Wait about 5 minutes for this coat to partially dry, then spray another wet coat over all parts of the instrument. Spray this second coat over the surfaces in the other direction (e.g. side to side). Alternating the this spraying pattern will help insure a more even thickness of the sprayed lacquer built coat.
- Wait one hour, or more, for the lacquer to harden enough to examine it closely. Examine all surfaces very carefully, and sand out any dust or foreign particles or roughness that are found. Sand with 320 grit WET-OR-DRY sandpaper and water. Lightly wipe the surfaces clean with a Tack Cloth just before spraying again.
- Spray two (2) more wet coats of the building lacquer over the entire instrument. Spray one wet coat over all surfaces. Wait 5 minutes before spraying the second coat.
- Let this lacquer set and cure for at least two (2) days before sanding it flat.
- Sand the dry lacquer layer flat
The process of building a musical instrument quality lacquer finish involves several spraying and sanding sessions over an 6 to 8 day period. This cycle of applying multiple coats of finish, letting the finish dry, then sanding it level is repeated several times before the finish is perfectly smooth and pore free.
The sanding - or leveling - of the lacquer between coats is at least as important as the spraying process is to achieving a quality finish. With each successive spraying and sanding cycle the lacquer coat gets thicker and flatter with fewer and shallower pore depressions on the surface. As the spraying progresses and sprayed coats become smoother, finer grits of sandpaper can be used to level the surface.
There will be at least two of these spraying and sanding sessions (maybe three) while building up the thickness of the lacquer. We will sand all lacquer surfaces with WET-OR-DRY sandpaper - of varying grits - using water as the sanding lubricant.
- Prepare the sandpaper and sanding pads for this sanding session. 220 grit WET-OR-DRY sandpaper will be used for this leveling. Fold a sheet of sandpaper in half, cut or tear it in two pieces. Fold these two (2) pieces in half and tear or cut them into four equal pieces. Cut or tear these four (4) pieces in half. There should be eight (8) individual pieces 2 3/4" X 4 1/4". Use the paper liberally, it works best when it is fresh and sharp. All eight (8) of the small pieces from one sheet will be used to wet sand the entire body. And last, make a 2" X 2 1/4" rubber or Styrofoam sanding pad to back the sandpaper during the wet sanding.
- Work in small areas at a time so that you may closely examine the lacquer surface and observe the progress of the leveling process.
- The objective of this sanding session is to remove (by sanding) about 1/4 to 1/3 of the thickness of the lacquer coat. This leveling should be even and uniform over the entire sanded surface. Pore depressions in the filled hardwood should be diminished but not entirely eliminated at this stage.
- Begin wet sanding. Wrap one of the small sheets of 220 grit sandpaper around the sanding pad and dab a little water on the instrument surface. Sand with moderate pressure repeatedly over the wetted area. Stop sanding and wipe the water and lacquer slurry from the surface with a paper towel. With the proper light examine your sanding effort very closely. Because you can’t see the surface as you work you must get a feel for the change in the surface made by your sanding. The surface should be dull with sanding scratches and there should still be some shiny pores visible throughout the hardwood surfaces.
- Continue wet sanding. Wet and sand this area again with the objective (see above) in mind. Wipe off the water again and examine the surface. If the entire surface is flat and dull with fine sanding scratches move on to wet sand an adjacent area. Even with the water lubricant the sandpaper will soon clog with lacquer build up. Replace the paper frequently, as needed, to keep sanding efficiently. It may take 2 hours to sand the entire instrument in this manner.
- BE CAUTIOUS - Sand each surface methodically, uniformly. Don’t over sand in any one area. Absolutely avoid sanding through this lacquer layer. DON’T TRY TO SAND OUT THE PORES COMPLETELY AT THIS STAGE. Avoid sanding right up to the edges of the top, back, and sides, too. It is easier to sand through the lacquer coat down to the wood surface at the edges than in the middle of the back or top. The lacquer surface at the edges will be sanded/leveled later in the process.
- This wet sanding session is completed when the lacquer surface over the entire instrument is flat, level and dull with fine sanding scratches. Every pore depression in the hardwoods should be at least partially sanded. Wipe the surface clean for another spray session.
- Spray more Building coats of clear lacquer
- Prepare to spray more coats of the building lacquer mixture. Mix additional “building” lacquer if it is needed. Wipe all surfaces with a Tack Cloth to remove any fine dust particles just before spraying.
- Spray four (4) wet coats of building lacquer over the entire instrument in the sequence outlined in the Spray the first building coats of clear lacquer section above. Spray two coats, wait an hour, spray two more as directed.
- Allow this new lacquer to set and cure for at least two (2) days before the next sanding session.
- Sand the dry lacquer layer flat
This new dried lacquer coat should be flatter and have far fewer tiny pore depressions on the surface than the first sprayed lacquer coat. This layer can be leveled by wet sanding with the finer 320 grit WET-OR-DRY paper.
- Prepare the sandpaper and sanding pads for this sanding session. We will use 320 grit WET-OR-DRY for this leveling. Fold a sheet of sandpaper in half, cut or tear it in two pieces. Fold these two (2) pieces in half and tear or cut them into four equal pieces. Cut or tear these four (4) pieces in half. There should be eight (8) individual pieces 2 3/4" X 4 1/4". Use the 2" X 2 1/4" rubber or Styrofoam sanding pad to back this paper during the wet sanding process. 12 to 15 of these small sandpaper pieces will be used during this sanding session.
- Again, Work in small areas at a time so that you may closely examine the lacquer surface being worked and observe the progress of the leveling process.
- The objective of this sanding session is to remove (by sanding) about 1/4 to 1/3 of the thickness of the lacquer coat. This leveling should be even and uniform over the entire sanded surface. All pore depressions in the filled hardwood should be totally - or nearly totally - sanded out at this stage.
- Wet sand this lacquer coating flat and smooth with 320 grit paper. Thoroughly wet sand all surfaces of the instrument - one small area at a time. Wet sand each working area until the surface is completely flat and dull with fine 320 grit scratches. Use fresh paper often for efficient, clean leveling. Wipe the water and lacquer slurry from the surface often to check your progress. Sand all areas methodically and uniformly.
- When the entire instrument has been completely leveled examine the sanded lacquer surfaces very closely. Use this close observation and your best judgment to determine which of the following conditions exist and proceed as directed.
- If the surfaces are completely flat, smooth and pore free - the building of the lacquer is complete. Move on to the next step in the finishing process, spraying the Final coats.
- If the surface examination shows that there are only a few small pores, pin holes, or gaps in the binding or rosette - these should be individually filled. The best method is to fill each tiny hole with straight, thick lacquer applied in multiple coats - 4 to 10 - with a very fine artist’s brush. Don’t drop a big glob of lacquer in the hole, but carefully brush multiple coats of straight lacquer into the holes over an hour or two. Lightly wet sand over these brushed pores or gaps to check the results of this filling
- If the surface examination of the leveled lacquer surfaces over the filled hardwood of the back, sides, and neck shows that there are still too many pore depressions evident - another lacquer Build coat is required over these areas. Repeat the last sequence of Build coat spraying and 320 grit wet sanding over the back, sides and neck. This third Build coating of clear lacquer over these porous surfaces will certainly leave them flat and pore free. Shooting more lacquer over the back, sides, and neck for a thicker, more protective coat is a common practice. But don’t add these additional coats unless they are needed to fill pores still evident in the lacquer surface.
- Spray the Final coats of lacquer over the entire instrument
The lacquer coating should be built up to a sufficient thickness at this stage. The intent of the Final coats of lacquer, then, is not to build more lacquer but rather to leave the final sprayed lacquer surface as flat, smooth and glossy as it can be. This very flat and smooth surface will make the fine sanding and polishing of the cured lacquer surface an easier task.
- Prepare the lacquer mixture for the Final coat. This lacquer solution will have more thinner and lacquer retarder than the Build lacquer mixture. Thin the McFadden’s Spray Lacquer FL128 about 33% with lacquer thinner (2 parts lacquer to 1 part thinner). Now add a small amount of Mc Fadden’s Lacquer Retarder FLRFT (very slow thinner) to the lacquer solution, enough to equal about 10% of the total solution. This Final-coat lacquer mixture leaves a thin, flat and shiny surface over the built-up lacquer film. Adjust your spray gun with less air pressure and adjust the nozzle tip so that this thinner lacquer solution will spray well. Carefully wipe off all surfaces with a Tack Cloth FTC to remove any and all tiny particles from the surface before spraying.
- Spray two (2) coats of this Final lacquer over the entire instrument. Spray with even, overlapping coats in one direction (e.g. up and down) over each surface. Wait about 5 minutes for this coat to partially dry, then spray another coat over all parts of the instrument. Spray over the surfaces in the other direction (e.g. side to side) for this second coat. Be especially focused on spraying perfect coats - evenly sprayed with every surface covered equally.
- Allow this initial Final lacquer coat to dry an hour or more. It should then be dry enough to handle. Closely examine every lacquer surface for any imperfections in the flatness and smoothness of the lacquer film. Level any minor imperfections with 400 grit WET-OR-DRY sandpaper with a lot of water and fresh paper. Sand only enough to remove or diminish the surface imperfection. Dry and clean the sanded surfaces.
- Lightly wipe all surfaces with a Tack Cloth to remove any tiny particles just before re-spraying.
- Spray two (2) more coats of the Final lacquer over the entire instrument. Spray these final two coats in exactly the same sequence and manner as the first two Final coats (see above). Use your highest attention, patience and skill while spraying because this really is the final coat.
- Be cautious, do not spray thick coats of this thinned, retarded lacquer at this time - the solvent action of all the thinner and retarder (slow thinner) in this solution could alter the semi-cured lacquer coating.
- Set the instrument aside for the lacquer coating to fully dry and cure.
- ALLOW THE LACQUER TO FULLY CURE
The time required for the sprayed finish to cure - dry and harden - enough to wet sand and polish to a high gloss is generally between 7 and 14 days. The fine sanding will go easier and the polished surface seems glossier with the longer drying time, but finishes with only 4 or 5 days of drying can be sanded and polished to an acceptable high gloss. We recommend the longer cure time - 10 to 14 days - for the best results.
- FINE SAND THE CURED LACQUER SURFACE
The cured lacquer finish should already be somewhat flat and glossy, but a close inspection will show that it is not glass smooth, or as shiny as glass. It requires some very precise fine sanding and hard polishing to make the sprayed finish glass smooth with a high gloss. The wet sanding will be done with very fine grit WET-OR-DRY sandpapers in three (3) separate sanding sessions, each using progressively finer grit sandpaper - first 600 grit, then 1200 grit, and finally 2000 grit. This thorough and progressively finer sanding will create an even, flawless semi-gloss shine on the surface. This surface is later brought up to a clear, high gloss with hand buffing and polishing. The more precise and thorough this fine sanding is - the easier and quicker the surface will be brought up to a high gloss during polishing.
- Prepare the fine sandpaper by cutting or tearing these 5 1/2" X 9" sheets into four (4) smaller 2 3/4" X 4 1/2" pieces to use with the sanding pad. To sand the entire instrument prepare at least eight (8) pieces each of these small pieces in the 600 grit, 1200 grit, and 2000 grit WET-OR-DRY sandpaper. Always use these smaller sandpaper pieces backed by a 2" X 2 1/4" rubber or Styrofoam sanding pad. This will help keep these lacquered surfaces very flat during the sanding.
- Prepare the soapy water lubricant for this wet sanding session. Add a couple of drops of dish washing soap to the water used as the wet sanding lubricant. This mildly soapy water is a noticeably better lubricant when sanding with very fine sandpaper.
- First sanding - Wet sand the entire instrument with 600 grit WET-OR-DRY sandpaper using the soapy water as a lubricant. This wet sanding session is very important to establishing the flatness of the final gloss surface. Sand evenly in all directions - with the grain, across the grain, at 45 degrees to the grain - with the same consistent pressure to create a flat, dull surface throughout the working area. Absolutely all small flaws, pore depressions, or imperfections in the surface are sanded out at this time. Use fresh sandpaper and lubricant often, and sand each lacquer surface to the same flat, dull (no shiny spots), flaw-free finish.
- Second sanding - Wet sand the entire instrument with 1200 grit WET-OR-DRY sandpaper using the soapy water as a lubricant. This is a much finer sandpaper and it is used here to sand out the fine scratches left in the surface by the previous 600 grit wet sanding. For this sanding session, move the sanding pad back and forth over the surfaces in one direction only - sand with the direction of the grain. This may make it easier to see the 600 grit scratches on the surface. Sand an area evenly and thoroughly. Examine the surface closely enough to see how the fine 600 grit scratches are removed by the even finer 1200 grit sanding. Be thorough here. Sand, examine. Sand, examine. Sand each area until all of the 600 grit scratches are completely removed from the surface. These finely sanded surfaces will now have a satin or semi-gloss shine.
- Third sanding - Wet sand the entire instrument with 2000 grit WET-OR-DRY sandpaper using the soapy water as a lubricant. This final ultra-fine sanding session may be shorter and easier than the first two. Wet sand all surfaces with the 2000 grit sandpaper. With moderate pressure sand evenly and uniformly from edge to edge - leaving the surface with a very fine semi-gloss shine.
- The fine sanding is completed and the lacquer surface is ready for polishing.
- POLISH THE FINELY SANDED LACQUER TO A HIGH GLOSS
At this point in our process it will be very important that all of the 600 grit sanding scratches have been totally removed by the previous 1200 and 2000 grit fine sanding sessions. The advantage of wet sanding these lacquer surfaces up to the ultra-fine 1200 and 2000 grits is that the very tiny scratches left on the surface by these ultra-fine sandpapers can be polished out to glass smoothness with a medium or fine liquid polish - such as the LMI Fine Polish FFP. Without the deeper 600 grit scratches in the surface there is no need to begin the polishing with the more aggressive Cut polish.
The entire instrument will be polished to high gloss with the Fine polish. Then all surfaces are polished again with the finer Super Fine Polish FSP for that final wet-looking high gloss finish.
- Make cotton cloth polishing pads. Just like we used sanding blocks and pads when we sanded the finish, we will use the liquid polish with a polishing pad. A simple polishing pad could be a tight, fist-size wad of cotton wrapped in a couple layers of soft multi-washed cotton - like an old white T-shirt. The soft cotton slides smoothly over the surface and the hard cloth wad inside the polishing pad makes a broad, flat semi-hard backing for this soft cotton polishing cloth. Make a similar, but smaller, polishing pad for polishing in smaller or tighter areas.
- Work in small areas - 4” X4” to 5” X 5”- and complete the polishing in each area before moving on to polish adjacent areas.
- Begin polishing the lacquer with the Fine Polish. Start the polishing by smearing a thin layer of the fine liquid polish FFP on the surface to be polished. This polish is the lubricant, and the abrasive, for the polishing pad. Hold the polishing pad tightly in the palm of your hand and begin polishing the surface with it. Move the pad constantly in a circular motion over the surface and press the polishing pad down harder to the surface as the polish dries out. When the surface polish seems dried out, wipe the dried polish off the surface and look closely to see the progress of the polishing - the surface will slowly change from satin to high gloss with successive polishing sessions..
- Continue polishing with the Fine Polish. Add a small amount of polish to the pad, or the lacquer surface, and aggressively polish the area again. Polish uniformly over the entire area. Stop and check the results. Add more polish and thoroughly polish the area again. Be patient. It may take 5 to 10 minutes and several buffing/polishing sessions to bring each small area to a high gloss. Use the smaller polishing pad or a small cloth to polish the lacquer in smaller areas and tight corners.
- End polishing with the Fine Polish. When every lacquer surface is polished to a high gloss with no fine scratches anywhere you can stop polishing with this Fine Polish. This entire polishing process may take two to three hours to complete. So don’t hurry, make sure an area is absolutely complete before moving to polish another.
- Polish all surfaces with the Super Fine Polish. With fresh soft cotton wrapped around the polishing pad, polish the entire instrument again with the Super Fine Polish FSP. This polishing session will go much quicker than the first and will bring the lacquer surface to an even higher gloss - almost wet looking. This Super Fine Polish can also be used to shine or clean the instrument at any time later.
- FURTHER COMMENTS AND PROCESS ALTERNATIVES
- The entire finishing process described here - from sealing the wood to polishing the cured lacquer - will take from 14 to 21 days to complete. We suggest using the maximum drying times indicated at each stage. This longer cure time at each stage will assure the best results from the wet sanding and hand polishing.
- Do not hesitate to spray the suggested third series of lacquer Build coats over the back, sides and neck if pore depressions are still evident after sanding the second layer of lacquer Build coats.
- Remember -- this is just one particular lacquering process among many that can achieve a musical instrument quality high gloss lacquer finish. Finishers with some experience may find it beneficial to slightly alter the mixtures of the lacquer solutions so that they spray well in their particular locale or shop situation.
- McFadden's Lacquer Retarder FLRFT is a useful tool in the lacquer finishing process. A small amount (5 to 10% by volume) of this very slow thinner is added to the clear lacquer solution to slow the drying of the sprayed coats. The lacquer will then lay out flatter on the surface before hardening. It would be beneficial to add progressively more retarder to the Build lacquer solution as it is built up during the three (3) spraying sessions. Increase the retarder added from 5% to 10% by volume on the third spraying over the back, sides, and neck - this will help the lacquer flow out flat and smooth over any pore depressions left in the lacquer surfaces at this stage.
- Our FINESSE-IT Polishing compounds may be used in place of the Liquid Polishing Compounds to hand polish the finish to a high gloss. Start with Finesse-It II F3MFIN to polish the sanded satin surface to high gloss. Use Perfect-It II F3MPER to buff this finish up to the final ultra-high gloss.