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More Plowden Progress

Graduation

Graduating hard maple can be a tough, laborious job. Besides, there is always the possibility of carving too deeply and ruining the plate. So, I try to cut the risks by creating a “map” by marking the thickness every few centimeters, and then carving the “dots” until each “dot” is about the thickness I want. Finally, I connect the “dots”, using planes and scrapers, checking for thickness as I progress.

Creating the dots. The circled numbers are already the correct thicknesses.

Grafted Scroll and Neck-Set

Once the graduations are complete, and the inside of the back plate has been scraped completely smooth, I install the label and I am almost ready to close the corpus. In this case, however, I also had decided to use the scroll I had carved, but graft a new neck to the scroll, as the original neck was too thin: so there was a good deal more work involved. Here is the grafted neck, partially shaped, with the completed back plate:

Completed back plate with neck-grafted scroll. The heel was still not shaped.

I had been anxious to complete the back plate, and had not yet set the neck. So I completed the neck and installed the fingerboard.

Next I set the neck, so that the angles were all correct.

Neck-set, front view. The mold is still in place.

Neck-set, side view. Notice that the neck heel has not been trimmed flush, yet.

Closing the Corpus

Then I removed the mold, and installed the inside linings on the back edge of the ribs, shaped the linings and the blocks, flattened the back of the garland, and installed the back plate. I use spool clamps and a single large spring-clamp to close the corpus. My wife thinks the spool-clamps look like old-fashioned hair-curlers.

Closed corpus with spool clamps and a spring-clamp.

Trimming the Button and Neck Heel

Once the glue was dry, I removed all the clamps, cleaned off any glue that had squeezed out of the joint, and trimmed the button and heel. The dimension from the juncture of the top edge of the front plate and the side of the neck heel (from each side) to the very center of the curve of the heel, should be right at 26 mm. You can see the two marks I laid out with a compass, testing that distance: it was still a little too high in the center of the curve, so the neck needed to be trimmed a little more.

Purfling the Back Plate

Once the neck-heel and button were trimmed, I still had to perfect the outline of the back plate, making certain that the overhang was even all around, as much as possible. Then I laid out the purfling slot, using a purfling marker, and began incising the outlines of the slot.

Incised purfling slot. It will be corrected, and fine-tuned as I work, and look good with the purfling.

Next I cut the slot out, using a small knife and a purfling pick, then dry-fit the purfling, after bending it on the bending iron. Finally I glue it in place, using hot hide-glue.

Edge-Work

I marked a crest-line, about 1.6 mm in from the outer edge, then used a gouge and scrapers to carve the channel, and fair it into the plate surface. The edges were all still quite rough,and crude, so I began shaping them, using a small plane, and a half-round file, then sandpaper to get a smooth edge all around. I don’t use sandpaper much, but this is one place where it is appropriate.

Trimmed purfling, smoothed channel, and edges taking shape.

The front edges have to be finalized as well.

Finishing Process Begun

Once all the varnish preparation is complete, I brush a coat of coffee all over the instrument, to tan the wood a little, and raise the grain. When that is dry, I sand off most of the raised grain, using 400-grit sandpaper. This ensures that the grain will not raise too much during application of the spirit varnish, later. Afterward, I rub in a coat of gypsum in a coffee suspension, to fill the pores of the wood with particles of the mineral. This keeps the varnish from saturating the wood, and possibly dampening the sound.

Mineral ground drying. See how it obscures the wood? that goes away when the sealer is applied.

Back with sealer. — The sealer renders the mineral ground transparent, and it will never be visible again.

I expect that, by tomorrow, the sealer will dry sufficiently that I can begin varnishing. I am getting anxious, as the show is a week from tomorrow, and I am far from completing this instrument.

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Closure and Final Scraping

Graduation complete

When I last posted, I was beginning the graduation process for the back plate of the Titian copy. I had a pretty busy week, but this is where it went:

Completing the graduation of the Back plate on the Titian Strad copy.

Once the graduation was complete, I removed the interior form (sometimes called the “mold”) from the garland, and trimmed the blocks and linings, so that the garland and back plate could be joined. I had already flattened the back of the garland, so this was a pretty simple step.

I aligned the plate on the garland as closely as I could, dry, then began applying clamps to hold it. I adjusted the position slightly as I progressed, so that when I finally had clamps on all corners, and in the center of each bout, the position was exactly what I wanted. Then I began removing two or three clamps at a time, and slipping hot hide glue between the plate and the garland, using a thin palette knife. I quickly replaced the few clamps I had removed, and more clamps between them, so that the section was securely attached. Then I moved to the next section and repeated the process, until there was glue and clamps all the way around. I saved the neck block for last, because I intended to add that larger clamp, and it would have been cumbersome, had I used it early in the procedure.

I allowed the glue to dry overnight, and, in the morning, I removed the clamps and began carving the heel, and working on the edges of the back.

Finally, all the surfaces looked right, and the next step will be to remove the fingerboard, and prep the entire corpus for the varnighing process. The Guarneri copy is side-lined for the moment, which is what usually happens when I attempt to make more than one instrument at the same time. I usually get to a certain point on all of them, and then run with one to the finish, and come back for the rest. (Ah, well…at least they do get done.)

Full Front view: ready for varnish prep.

Next time, I will either talk about the varnishing preparation process, or I will follow the work on the Guarneri. Probably the varnish-prep. 🙂

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