The pearl slide has been fit. This step begins with selecting the shell. Most often I use Japanese abalone which is known as awabi. As with all bow making materials finding the highest quality shell is a task in itself. Once the maker has found a source for the awabi and purchases a quantity he or she must sort it out. I would expect a yield of 20-30% on average of usable shell. Shell is prone to many defects. The maker will pick out a gorgeous piece only to find a tiny crack, blemish, chip, or hole from some tiny invasive predator. It can be heart breaking really to have to pass up some otherwise lovely material.
Once the piece of shell has been selected I thin it out from approximately 1 mm in thickness to about .6 mm on a diamond stone. Now it is thinned it is glued to a 1 mm thick piece of ebony. After the glue has set it is filed to match the dovetails seen in Cello Frog Series #3. The taper is filed to match the channel or coulisse and the slide is slowly fit. When it reaches the back of the channel against the silver talon or heel plate it is filed to match. The front of the slide is then cut off with a jeweler’s saw and the front is filed to match the ferrule or passant.
Returning to the top of the frog the coulisse for the silver underslide is created using chisels made specifically for frog making by local artisan Ed Louchard http://www.zephyrwerks.com/contact.asp. One of these chisels can be seen to the right of the frog in the photo. I made the handle from Bubinga wood and did a short silver wire wrap that is similar to a winding on a bow. Ed has made some beautiful tools for me based on old French models provided by Charles Espey. I will devote some time in future posts to the tools and French method. The channel that you see in this photo was created entirely by hand with chisels and the base was finished with a fine file. Early French bows were fit onto the stick as you see this one. That is to say the silver under-slide wasn’t used until the early 19th century. I have made several bows in this fashion. You can see a photo of one at the following link, look for my 2006 gold medal winning cello bow. Notice that there is no line of gold in between the frog and the stick. http://www.robertmorrowbowmaker.com/bows/indexflash.html It is possible that the under-slide has a dampening effect on sound quality. The bows that I have made without under-slides have been well received. The trade off is that the ebony is fragile and can easily be damaged by careless work while re-hairing.
The silver under-slide has been fit, glued in place, pinned with silver pins, and filed flat. I make the under-slides on a steel form made by local machinist Wayne Meginnes. The hole for the eyelet is drilled at this time as well.
In the next post we will move on to the stick.