For many luthiers, joining the bookmatched backplates together is their first glimpse of what the finished instrument is going to look like!
There are three basic methods for getting the edge of the plates ready for joining: using a jointer, using a hand plane, or using sandpaper attached to a flat surface. Of course, it’s most common to see people using a combination of these tools. We will not be entertaining the well-worn debate about whether a blade edge is better for gluing than a sanded edge in this blog! What is not debatable is the advice to clean the wood’s edge with a solvent prior to gluing. This is especially true with the Rosewoods which have a high oil content. Acetone is a popular choice. Just clean the edge and glue up right after the solvent has evaporated, typically just a minute or two.
There are two ways to include a decorative backstrip. The first is to join the plates and then rout a channel down the center to accommodate the backstrip. Some feel that this creates the most secure joint as the backstrip functions as a reinforcement of the joint in some respects. The second method is just to sandwich the backstrip between the plates and glue all the pieces together at once.
LMI offers a great variety of decorative backstrips, which are thick enough to be sandwiched (or easily inlaid). In addition, you could use a combination of bindings, wood strips, and purflings to come up with your own motif. For gluing the plates, you can’t go wrong with LMI’s popular Plate Joining Jig (PJJN).