edgework

September 22, 2016September 23, 2016

Finishing Sequence Part One

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Beginning of the Finish

We looked last time at the viola with the edgework incomplete, and final scraping not done.

Here is the viola with the edgework done. Notice that the outer edges have been rounded inward to meet the edge crest, so that the junction between edge crest and purfling channel makes a clean ridge around the perimeter of the viola. This is just something I do, because I like it…as far as I know, it has no functional value. Many old master instruments have a much less clearly defined crest.

Coffee Stain and Re-smoothing

Then I wet the fiddle down with coffee, to raise the grain and add some color. One result is that my edgework all needs to be reworked with a small, sharp scraper. The other is that the whole instrument needs to be re-sanded, using 400-grit sandpaper. The water in the stain raises the grain, so that every random fiber that is not closely tied to the surface will swell, and raise up, making the whole surface very rough. So I deliberately raise the grain, and then scrape or sand off the rough surface. Using a very sharp scraper, very lightly, just “brushing away the rough stuff” is probably the best way to do this. I use a scraper for the areas where I want detailed, clean edges, and 400-grit abrasive paper for the broad surfaces. I perform this step at least twice, before moving on to the mineral ground. The result is a surprisingly light, yellow-tan color, all over. Almost just a cream-color. It will darken up nicely under varnish, though, and not glow white from under the varnish.

Come to think of it, the above photos already have the coffee stain, too. I forgot to take photos of just the edgework, I guess. So–those photos are right before I applied the mineral ground.

Mineral Ground

This is a suspension of very fine particles of gypsum…in a coffee-solution, because I still want to add more color, if I can. Other people use other minerals–finely ground mica, finely ground glass, microscopic beads of glass, clay, volcanic ash or other non-organic nano-particles. Some omit this step entirely. Roger Hargrave shared this as having had an important effect on his sound, so I have tried it, for the last several instruments, with what seem to be positive results.

I keep the solution well-stirred-up, and brush it on liberally, then rub it into the wood with my fingers, as vigorously as I can. Finally, I wipe off as much of the excess as I can, using a rag. The stuff goes on looking brown, because of the coffee, but dries to a chalky-white film. I don’t particularly want it on the wood– I want the microscopic particles to fill the pores in the wood, so that the varnish will be less likely to soak deeply into the wood, and deaden the sound of the viola.

The ground dries rapidly, leaving the whole viola a chalky-white, ugly object. I go over the dry instrument, checking everything, and scraping or sanding off all the excess ground. When I can see the grain of the wood everywhere (though dimly) through the gypsum film, I apply the sealer coat.

Mineral Ground, wet...back view — Mineral Ground, wet…back view.

Ground drying — The ground dried rapidly– this was only about three minutes after the above picture.

Mineral ground drying — And this was only about five minutes.

Dry Mineral ground — Here it is, dry–without the flash. In daylight this is chalk-white. See how the grain is obscured.

Mineral ground dry front view — And the front– you can see the excess pretty easily.

Here, you can see the excess ground in the f-holes, and along the purfling.

All that excess gypsum had to come off. It took a while, but I got it ready to seal:

Viola front is ready for sealer– all the excess mineral ground has been cleared away.

Back ready for sealer — The back, ribs and scroll have been prepared, too. All are ready for the sealer.

Sealer–What kind?

Different makers use different sealers:

Some use a very thin varnish.
Some use Rosin-oil (I’m not even sure what it is….)
Some use shellac.
Some use commercially available sealers.

Currently, I am using a very thin mixture of pine pitch and turpentine, with a little alcohol. The alcohol and turpentine cause the mix to penetrate deeply. The pine-pitch goes into the wood along with the solvents, and remains there. It is interesting to watch the sealer going on…the chalk-white gypsum instantly turns transparent, and effectively disappears, leaving the natural color of the wood, along with whatever staining was added.

Without adding any color to the sealer, this would leave the wood a somewhat pale color. Usually, I have been satisfied to add color later. I added a little amber color to the sealer, this time, though, because my last instrument was a little too light-colored, initially, and I didn’t like the result.

The alcohol evaporates nearly immediately, while the turpentine takes a few days to evaporate, and (I am told) it leaves a bit of residue, as well. But that is OK. Turpentine is a natural wood extract, and I don’t mind it being in the wood.

The pitch dries in the wood, locking the gypsum in place, and sealing the wood against any other substance. Again, the pine-pitch is a natural wood extract, which eventually dries hard, and I don’t mind it being in the wood. Besides, it smells nice. 🙂

Here is the viola with just the sealer. I will show the varnishing sequence in the next post.

Sealed viola back — And…here’s the freshly-sealed back; again, using the flash.

The wood will change color just a little as the sealer dries. But it will never go back to the dull-looking finish where the grain is obscured again. The varnish I apply will enhance, not obscure the figure in the wood…I hope. 🙂

Varnish (coming…)

I use a spirit-varnish, currently, though I have used oil varnishes in the past, and undoubtedly will again. I will start off with a yellow varnish to enhance the figure in the wood, then use darker coats to finish. I use enough coats to get the color the way I want it, including whatever shading I choose to do, then add enough clear coats to give it the depth and sparkle I want. Usually 6-8 coats, I guess. I sand lightly after virtually every coat, to reduce any bumps, sags, runs, or brush-marks, as well as looking for brush hairs or bugs, stuck in the varnish film (it happens….)

Finally I rub the surface with extremely fine abrasive (12,000-grit micro-mesh), and then polish it all over, using the dry skin of my palm, or thumbs, rubbing hard enough that the varnish gets uncomfortably hot. This takes away the “glittery” look of the fresh varnish, and leaves the glow of hand-rubbed work. Pictures in the next weblog post.

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July 24, 2016

“Beginning of the Finish”

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Finishing My Newest Violin

Introduction:

For every violin, viola, five-string fiddle, cello or double bass I build, the finishing process is nearly the same. After completing the last of the purfling, the order is as follows:

Channel (the concave curve in which the purfling is nearly centered, but which must fair smoothly into all the other surfaces, concave or convex.)
Final edgework (making the outer edge (and inside of the plate) curve together into the channel and arching)
Varnish prep (final fairing-in of all curves and elimination of all bumps and unwanted ridges)
Water-based stain (usually two or three applications)
Mineral ground (one application)
Seal-coat (one application)
Varnish (numerous coats)
All set-up issues: saddle, fingerboard, nut, pegs, soundpost, bridge, endpin, strings, tailpiece and (on the smaller instruments) chinrest.

The Channel, and Final Edgework:

I scribe a margin around the entire outer edge, usually about 1.6mm in from the outer edge. This will serve as the “limit” for the channel. I cut the channel to the desired depth, using gouges first, then small planes and scrapers, bringing the smooth curve up to match the scribed limit. Then I file the outer edge so that it curves in from the center of the edge of the plate up to meet the scribed margin of the channel. The other margin of the channels are scraped so that they fair into the curve of the plates themselves. I true-up all my lines using scrapers, files, and very fine abrasives, and then I am ready for final varnish preparations.

On my last post, I had just completed the back purfling. That seemed a good place to “call it a night”.

Back purfling complete: the channel has not been started. You can see the sharp edge of the purfling in a few places.

Then I began preparations for cutting the channel, by scribing in the boundary line:

Scribed line, marking the edge of the channel.

Scribed pencil lines where the channel will go at the corners. (I didn’t use the flash on this one–that’s why the color is different.)

Beginning the channel cut. The purfling looks cleaner, as the rough, glued edge is gone. I also began shaping the edges.

Varnish Preparations

I have a particular spot on my basement stairs, where I can get a very low-angle, not-too-bright light source, which casts shadows across the face of the instrument, and makes is easy to see irregularities. So, the last thing I do is stand there, holding the fiddle and rocking it very gradually, to see any shadows that indicate a rough spot or an irregular shape. When I find one, I gently scrape it away with a very sharp scraper. I want to move as little wood as possible at this point in the build: I already have the arching and graduation just about exactly where I want them to be. This is strictly fine-touch finish-scraping.

Some people are very particular about not using ANY abrasives. Sorry– I do use them, in a very limited way, but only at the very last part of the build. The edges of the spruce plate, for instance, are so soft that a scraper is simply too aggresive for final shaping, especially after I raise the grain with my water-based stain (strong coffee, in my case…yes, and I drink the leftover “stain.”) So I use a very fine (worn 400-grit) abrasive paper to make the edges smooth and pretty. I also use it later, between coats of varnish, to make sure that no bits of dust, splinters, etc. can spoil the next successive coat(s) of varnish.

Channel complete...no flash. — Channel and edgework complete…no flash. The wood isn’t really this yellow– we have a fairly dark house, and the sunlight filtering through makes it look this way.

Completed channel, with flash — Same shot of the completed channel, with flash. This is pretty close to the real color at this point.

Coffee Stain

I use a coffee stain because it imparts a gentle yellowish look to the wood, without doing any damage to the wood. Many people use strong tea, and I have done so. Some have a particular tea they use, for the color they want. That is fine. Some have alcohol-based, color-fast dyes to accomplish a similar result. That is OK too. I’m just telling you what I do. People have sometimes asked whether I use de-caf or regular. I love that question: I say, “Oh I always use regular, to wake up the tone!” 🙂 (Riiiight…)

Mineral Ground

This is something I got from Roger Hargraves. He is a master luthier living in Germany, and he wrote an online book as he built a magnificent double bass. In it he explained why he uses a mineral ground, and what it is (it is effectively exceedingly fine gypsum dust, introduced into the wood pores in a liquid suspension. He used a very thin varnish as I recall…I used coffee, again. It dries slowly, is easily applied, and cleans up with water.) So, I apply the mixture with a brush, one area at a time, rub it in with my fingers, and immediately rub back off as much as I possibly can, using a rag. I do NOT want a thick layer of stuff on top of the wood– I want the pores themselves to be filled with the particles. I coat all areas except the “handle”portion of the neck in this manner. Supposedly it leeps the varnish from saturating the wood, thus avoiding overloading the wood with varnish and deadening the sound. Does it help? He says it does, and I know for a fact that he did it…and I saw the bass in person, last year at the International Bassists Society convention, in Ft. Collins, CO.

The ground dries chalk-white, in spite of the fact that I used coffee for the liquid. I sand it gently to remove any excess gypsum (there always is a fair amount that comes off the surface at this point). Sorry, I didn’t take a picture at this point. You’ll have to take my word for the fact that it simply looked like a chalk-white violin, with the grain and purfling quite obsecured by the dry mineral ground.

Sealer

Then I seal the violin, all except the “handle” portion of the neck. There are many things people use for sealer: Some use special commercially available preparations (I have done that, too), and some use very thin varnish, or shellac. For now, my sealer is a combination of Pine sap (yes, that sticky gunk that flows out of a cut in a pine-tree) and turpentine. The turpentine penetrates the wood very readily, taking the pine pitch with it. I allow the turpentine to evaporate off, leaving the pitch in the wood. I am of the opinion that the pitch is an OK thing in the wood, and that it seals the wood against further penetration by varnish. That’s my theory, anyway. 🙂 The mineral ground turns completely transparent under the saturation of the turpentine and pine pitch, and remains that way after the turpentine evaporates. Here is a photo of the violin with the mineral ground rendered transparent by the sealer. It will probably take a few days to get absolutely dry, (turpentine evaporates slowly) so this is the last photo for this post:

Varnish

I have used a wide variety of varnishes, but currently I am using a spirit varnish concoction. If I need more color, I use the “Transtint” dyes available in woodworking stores and online. It does not take a great deal of dye…you want to go easy on this stuff. I have considered extracting dyes from plants, etc. Never have gotten around to it. 🙂

I’ll show the varnishing process in the next post.

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July 21, 2016

More Progress on the “Plowden-model” Violin

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More Progress: The Plowden-model looks like a violin!

Removed the Mold and Installed the Back Linings

One nice thing about this (French-style) mold is that it is easy to remove– it usually takes less than five minutes to get it out, provided I have waxed the non-glued surfaces of the mold, so there is no chance of an accidental adhesion to the ribs. I simply use a flat chisel to crack the glue loose at each block, where it is attached to the mold, and then slip my parting knife (in reality, it is an old potato knife) between the block and the mold, to make sure nothing is still adhering to the mold. After that I can slide the mold out by lifting as shown, while wiggling each individual block to make sure they are all moving evenly. The only drawback is that I have to install the back linings after the mold is removed, and the rib garland is pretty fragile. In the past, I have used a two-part collapsible mold, in the italian style (centered between the front and back edges of the ribs); but it is more difficult to remove. The only real advantage is that I can install all the linings while the corpus is still on the mold, and still get the mold out without too much trouble. I believe it does have a slightly greater tendency to leave the ribs slightly convex in the center, as well, and some people find that attractive. (I do too…. Perhaps I will eventually go back to using the Italian-style molds.)

Back before mold removal. You can see how thin and fragile those ribs are.

This time, the linings went in without a struggle, though, and the whole task took about 30-40 minutes. A few hours later, the glue had dried, and I was able to remove all the tiny spring-clamps, and get going on leveling the back of the garland, and cleaning up the interior.

Back linings installed, ready for shaping and smoothing.

Blocks and linings before shaping and smoothing. I had trimmed the front side of the blocks, and the front linings, before I installed the front plate.

Blocks and linings shaped, ready for scraping and smoothing. The blocks and linings are weeping willow…the bass bar is Sitka spruce.

Cleaning up the Interior

Cleaning the interior primarily means shaping the linings and blocks, after the mold is out of the way, but it also is a final opportunity to scrape any rough spots, and make any minuscule repairs. So, I put on my magnifying visor, and look things over very carefully. I use a knife to trim the linings so that they are triangular in cross-section, thickest at the edge, to suport the edge of the rib, but tapered so as to not restrict the vibrations of the middle of the ribs too much.

One thing I have to remember, at this point, is that it is also my “last shot” at the interior of the back plate, so, before I install it, I carefully check and scrape it, and, as a final “seal of approval”, I install my signed and numbered label, gluing it in place where it will be visible through the bass-side sound-hole. All my instruments are individually hand-crafted, and each ends up a signed and numbered original, not a mass-produced instrument. I’m really not interested in doing things the “factory” way.

Installing the Back Plate

I used to complete all the work on the back plate, including purfling and final edge-work before installing it on the garland. But I have recently altered my order of operations so that I purfle and do edgework after the plate is installed. This allows me to adjust the plate overhang boundaries, and make final decisions as to how I want things to look, before permanently locking the shape in place by installing the purfling.

I also used to “self-induce panic,” by spreading hot hide glue around the perimeter of the garland and plate, and then frantically trying to align the edges perfectly and adjust all the (25-30) spool-clamps, etc. before the glue gelled. That was a fool’s-errand, as the glue usually gels far more quickly than I could ever get everything clamped in place. The late Sam Compton shared how he applied the glue and allowed it to gel, then aligned everything at a leisurely pace, gently clamping everything in place. Afterward, he went around the perimeter with a hair-dryer, gradually warming the plates until the glue re-liquefied. Finally, he tightened the clamps just enough to completely close the joints. Pretty clever.

I ended up clamping everything dry, then loosening a few clamps at a time, and slipping the hot hide-glue into the seams, using a very thin palette knife. That seems to work pretty well, and definitely eliminates stress. (His method probably is even better, but this is how I do things, for now.)

Back plate glued in place, using hot hide glue and spool clamps.

Label visible through f-hole. The f-holes still will require quite a bit of smoothing.

Final Edge Shape and Purfling

Once the back is securely glued in place, I can trim the edges to exactly the shape I want, so that the overhang is matching the front plate, etc., and then begin purfling.

Front view: back plate has been installed and trimmed to size.

Back plate installed. Side view, before purfling and edgework. — Side view, before purfling and edgework.

Back plate installed and trimmed to size, before purfling and edgework. — Back view: before purfling and edgework.

I use the purfling marker to scribe in the double lines (except for the corners) where the purfling will be inlaid. I then draw in the corners very carefully. I have occasionally used a template for the corners, but it seems to not always work, since the corners are not always exactly the same. So I end up just making some layout marks to get the limits delineated, and then I draw the corners in, freehand.

I incise the purfling slot with a small, sharp knife, in three or more steps:

The first pass with the knife is very shallow and light, only serving to deepen all the scribe marks.
The second and third passes bring the purfling slot to the correct depth, and
The last step is to use a purfling pick to remove all the waste wood between the paired cuts.

Purfling slot partially completed; — One-piece European maple back: the Purfling slot is partially completed; but still too shallow, and a little too tight.

Purfling slot complet — Purfling slot is completed… it turned out to be a little too tight: I used a tiny sharp knife to trim the tight spots, until everything fit.

I check the depth and width of the slot by inserting a small section of purfling into the slot, all the way around, until I am sure that the slot is correct. then I bend and fit the purfling strips, and make sure the fit is as exact as I can make it, terminating in the classic “bee-stings” at the corners, rather than a simple “mitered corner.”

Finally, when all is as close to perfect as I can manage, I lift each section of purfling partially out of the slot, one at a time, and slip hot, thin, hide glue into the slot, using the thin palette knife again. I press the purfling all the way down to the bottom of the slot, and allow the glue to dry before beginning the final edgework.

Back purfling completed. Channel still needs to be cut and edgework is still untouched.

The Channel, and Final Edgework:

I scribe a margin around the entire outer edge, usually about 1.6mm in from the outer edge. This will serve as the “limit” for the channel. I cut the channel using gouges first,then scrapers, and bringing the smooth curve up to match the scribed limit. Then I file the outer edge to round in from the center of the edge of the plate up to meet the scribed margin. I true up lines using scrapers, files, and abrasives, and then I am ready for final varnish preparations.

We’ll talk about all that in the next post, and post pictures. I need to get this one wrapped up. I’ll show close-ups of the edges and corners next time. there is still a long way to go, but it is looking more encouraging. 🙂

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September 25, 2015September 25, 2015

5 String Fiddle Progress Report #13; Completing the Purfling Weave

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Five-String Fiddle Purfling Weave

Over and Under Illusion

Some makers, especially those making violas da gamba, Lutes, etc., make much more complex purfling weaves. Some of the Celtic designs employ the technique in very sophisticated ways. The point is to make an illusion of 3-D “over and under” weave in the purfling. As far as I know it has zero effect on tone; just appearance.

Installing purfling

When I left off, last post, the purfling groove was nearly complete, but not quite: I finished picking out the last bits of wood in the “fleur de lis” areas, then went all the way around checking for depth and width.

My purfling bending “iron” is an old-fashioned solder-iron affixed to a brass cylinder with various diameters. I don’t know who made it…I got it from my friend Jake Jelley.

Starting with the completed purfling groove, I first cut and bent the center-bout purfling strips, and inserted them into the grooves, making sure the mitered ends were all the way into the corners of the “bee-stings”, as the sharp miter-ends are commonly called.

Then I cut and bent the long upper and lower bout strips, and fitted them carefully into place, jamming them tightly into the miters at the corners, and trimming them to fit exactly at the other ends.

Dry fit lower and center bout purfling strips

Then I began gluing the long strips in place, so that they would stay put while I installed the short ones. I tipped the center strips up and inserted hide glue in the groove, then pushed them back in place, and forced them to the bottom of the groove, so that the glue was squeezed out all the way along each strip. Then I repeated that procedure on all the upper and lower-bout purfling strips. Afterward, I could begin work on the “fleur-de-lis” designs.

Second side lower bout purfling dry fit — Fleur-de-lis design begun

The “Weave”:

You can see that I had to decide, initially, which strip goes “over” and which goes “under”: In reality, of course, they are all at the same level, but, choosing which gets cut off (thus looking as though it goes “under”) and which goes on through an intersection (thus appearing to go “over”) determines which way the “weave” seems to go. Once I pick a direction, I need to pay close attention to see that it continues with the “over and under” look, to make the “weave” illusion appear correctly. I also try to make both ends the same way (starting “left over right”, for instance).

Lower purfling weave complete, ready for final scraping and edgework (which has not been begun.)

Purfling weave completed: next step will be to cut the channel.

All that is left on the back, now, is the channel, the edgework, and final scraping. We are officially “on the home stretch!”

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