Posts Tagged ‘Mineral ground’

Beginning the Finish

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Beginning the Finish

Pre-varnish Scraping and Shaping

Before any finish materials can be applied, the wood has to be about as perfect as I can make it: so I scrape it to its final shape, then dampen it with coffee, to simultaneously raise any fibers that had only been flattened by the scraper blades, but not smoothly sheared off, and, hopefully, add a slight “tan” to the wood, while doing no harm.

Thus, having removed the fingerboard (which had only temporarily been installed) and having applied two coats of coffee, allowing the wood to dry between coats, and having sanded lightly, all over, with 400-grit paper, to remove the raised fibers, and any excessive “corduroy” effect, the instrument went from looking like this:

Shaping complete, but wood un-treated.

Shaping complete, but wood un-treated.

 

To looking like this:

Coffee-stained, and sanded with 400-grit.

Coffee-stained, and sanded with 400-grit.

 

Then it is time to begin the real finish: I first coat the wood with a coffee-suspension of very fine, powdered gypsum, hoping to add more color as I fill the grain with the gypsum. I vigorously rub this suspension into the wood, hoping to encourage the tiny particles of gypsum to actually settle into the pores of the wood, so as to fill them, and to slow down the absorption of varnish. It is considered undesirable, in general, to have the varnish really soak into the wood, as it tends to dampen the vibrations that make the sound. Some varnishes are more detrimental than others, but this is something I learned by reading Roger Hargrave’s notes. He is a world-class expert, so I tend to believe him that this is a good idea. I try to remove as much as I can of the excess mineral “ground” before it completely dries, rubbing hard, with a rag, but any that has settled into grain irregularities, I simply skim over, and leave it there.

So, after the gypsum has been applied, it looks more like this:

Mineral ground applied, front view.

Mineral ground applied, front view. A little darker color, and the grain is more obscure.

 

Back grain quite obscured by the gypsum.

Back grain quite obscured by the gypsum. That will clear up entirely, with the application of the sealer.

 

The sealer locks the gypsum into wherever it has been lodged, and clears the obscurity, making the gypsum completely invisible. The sealer I am using now is a concoction of pine resin, turpentine, and alcohol, with a little yellow tinting. The turpentine and alcohol evaporate, leaving the resin in the wood.

Sealed Front.

Sealed Front.

 

Sealed side.

Sealed Side.

 

Sealed Back.

Sealed Back.

 

After the sealer dries (a day or so), I begin applying the various coats of varnish: the first two or three coats are fairly yellow varnish, but after that, I begin adding the colors that will characterize the finished instrument.

Front with yellow varnish.

Front with yellow varnish.

 

Back with yellow varnish.

Back with yellow varnish.

 

From this point, forward, the instrument will become increasingly darker, leaning toward reds and browns. Ultimately, I will try to emulate the look of the 1715 “Titian” Stradivarius violin, after which this insrument is supposedly modeled. We will see how it turns out.

 

Thanks for looking.

 

 

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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.

Edgeork incomplete

Edgeork incomplete

Edgework

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.

Edgework complete, back view

Edgework complete, back view

 

Edgework complete; angled view.

Edgework complete; angled view.

 

Edgework detail

Edgework detail

 

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.

 

 excess ground

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

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 Front

Sealed Front., using the flash.

 

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.

Thanks for looking.

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Varnishing Sequence; Part Two

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Varnishing Procedure; Part Two

Leveling the early coats of Varnish

In the last post, we were looking at the third coat of varnish. It looked pretty raw, still. You can imagine how much brighter the white wood might have looked under the varnish, without having stained it first. Some people hang their newly made instruments out in the sun, so that the ultraviolet light oxidizes the wood somewhat, and darkens it quite a bit. (Especially those who live where the sun actually shines: I, on the other hand, am in western Oregon, where the sun is a novelty… I do have a U.V. cabinet, but have not been very impressed with the results, so I haven’t been using it.)

Violin back with three coats of varnish.

Violin back with three coats of varnish.

Something I have occasionally done is to apply a few coats of varnish, then strip it all back off, down to the wood. It does not affect the mineral ground, nor the sealer, but it does affect the foundation color of the wood, much improving the finished look. But it is a lot of extra work…so I have only done it a few times.

Regardless of how I accomplish the color I want, the next step is to level the varnish.

I use fine abrasive paper (400-grit), to gently remove any bumps, and to leave a matte-finish all over the violin. I am very careful to not fully remove the texture of the raised grain, left from the coffee stain, but only to scuff-up and smooth the varnish itself. The wood should have been the way I wanted it before I began varnishing. I prefer that my violins still have some “wood-texture”. Some people like the mirror-bright plastic look, but I don’t. On a guitar, that is one thing. These are supposed to be concert violins… another thing entirely.

The things I am especially vigilant about are sags, drips, runs of any sort, and brush-hairs, etc. If there is an actual flaw in the varnish, I want to remove it before I move on. But, many times, I will deliberately (later) fill any “texture” with a darker substance, again emulating the “wear and dirt” of old instruments. I limit this to pretty minor stuff, usually. I have known fellows who took “antiquing” much further; as in, breaking wood off corners, etc, and abrading away varnish right into bare wood, then rubbing dirt into the wood. Sorry…I am not going to do that. 🙂

The important thing is to realize that any anomalies in texture will be highlighted by the varnish, not hidden. Something as small as a brush hair or a speck of sanding dust will become terribly obvious if one continues to varnish over it. (I learned this the hard way….) The varnish piles up around it and literally makes a mountain of a molehill. It pays to take the trouble to get things smooth before you move on.

Completing the Varnishing Sequence

I try to make sure that each layer of varnish actually contributes what I want; building toward the whole effect. So, I have to decide when to do any shading or antiquing. I have to decide how much extra color to apply in the darker areas, and what the overall color impression is to be when a person first sees the violin: Dark? (How dark?) Antiqued? (How much?). So, there usually comes a point where I decide the violin is dark enough, and I add two or more additional coats of yellow or clear varnish to increase the feeling of depth, and to shift the overall color impression back toward golden. Sometimes that works well; sometimes it does not. Occasionally I have had to give it up, strip the fiddle, and start over. 🙂

So, here is the rest of the varnishing, in the order it actually happened:

I neglected to take a picture of the fourth coat of varnish, but it wasn’t all that different from the third…same varnish, etc. So, here is the

Fifth Coat:

Fifth coat of varnish...side view of new violin.

Fifth coat of varnish…side view of new violin.

 

fifth coat varnish front of violin

You can see the areas where I have left thin varnish, to imitate the look of an area where varnish is worn off. I will sand them, later, to add realism.

 

fifth coat varnish back of violin

And, the back! Again, you can see the “wear” areas. The varnish is taking on some of the depth of color and clarity that I enjoy.

 

After the varnish dried overnight, I gently sanded it again, then added a sixth and seventh coat. Here are the photos:

Sixth Coat:

This one was mostly a case of adding strong color in the areas I wanted darker, and virtually none in the areas I want lighter. There was a tendency to streak, so I would feather the transitions out, using a fine sable brush, moistened (not wet) with alcohol. It worked well, but, if you look closely, you can still see streaks. These will be smoothed before the seventh coat, either by the alcohol method or by sanding. It is important to realize that, on the flamed maple, your brush-strokes should follow the flame, and on the spruce, follow the grain. In both cases, the natural lines in the wood tend to disguise any leftover brush-marks.

Sixth coat of varnish: adding dolor in selected areas.

Sixth coat of varnish: adding color in selected areas.

 

Sixth coat of varnish on back

Sixth coat of varnish on back; adding color in selected areas.

 

I allowed the sixth coat to thoroughly dry, then sanded it with 400-grit, well-worn abrasive paper, and applied a final “color-coat”: after this one, I will only add yellow or clear varnish, to accentuate depth or shift the color range toward gold.

 

Seventh Coat:

Seventh coat (final

Seventh coat (final “color-coat”. ) It doesn’t look very different from the sixth coat, but, in person, the thin areas are less “dry-looking.”

 

Seventh coat of varnish on the back of the violin.

Seventh coat of varnish on the back of the violin. The neck shows the original color of the wood. It will be stained and sealed at the very last step before set-up.

 

Eighth Coat:

I doubt you would really see a great deal of difference in this coat. The photographs are not very accurate in terms of color– I guess the flash does that. They are too red, and too bright-colored. It is not really that bright, but the color is shifting back toward gold, as I apply the last two or three coats in yellow varnish.

Eighth coat (yellow varnish)

Eighth coat (yellow varnish): This is nearing completion. There will be some minor retouch after everything else is done, but this is pretty much the way it will look.

 

eighth coat back

Again, the colors are not very accurate…but it does look nice. Just not this bright.

 

So: I think that is about as far as I will take the color, for right now. I will very likely decide later that I want it darker, and, if I do, I can always add more color. But I think I will go ahead with the saddle, fingerboard, nut, etc. and see how I feel about it. If I decide it is fine the way it is, then I will go forward with set-up. If I want it darker, I can add color at that point, and another yellow or clear coat, and then do set-up.

So, that is as far as it is going tonight.

Thanks for looking.

 

 

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“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:

  1. Channel (the concave curve in which the purfling is nearly centered, but which must fair smoothly into all the other surfaces, concave or convex.)
  2. Final edgework (making the outer edge (and inside of the plate) curve together into the channel and arching)
  3. Varnish prep (final fairing-in of all curves and elimination of all bumps and unwanted ridges)
  4. Water-based stain (usually two or three applications)
  5. Mineral ground (one application)
  6. Seal-coat (one application)
  7. Varnish (numerous coats)
  8. 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

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 line, marking the edge of the channel.

 

Scribed pencil lines where the channel will go at the corners.

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.

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…)

Coffee stain, not fully dry yet.

Coffee stain, not fully dry yet. I used the flash on this, so the color change is real.

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:

Mineral ground renedered transparent by sealer coat.

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.

Thanks for looking.

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5-string report #15: Varnishing

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Five String Progress Report #15: Varnishing

Mineral Ground

I did not take any photos of this process…it only consisted of rubbing a gypsum suspension into the wood, all over, then rubbing it off, as completely as possible. The goal was to fill the wood pores, so as to limit the penetration of varnish into the wood. Apparently the varnish tends to dampen vibrations, and deaden the violin sound just a little. I don’t know how much effect it really has, but I got the idea from Roger Hargrave, who said it made a difference in his work. If it is good enough for him, I am game to try it. My suspicion is that my ears are no longer good enough to hear the difference, due to a lifetime of work in heavy steel. But…I have had very good reviews on the few instruments on which I have used the ground, so…either it really helps, or I have just improved my building skills, lately.

Sealer

My sealer is pretty simple: it is raw pine pitch dissolved in a combination of pure spirits of gum turpentine and alcohol. It penetrates pretty deeply, but the alcohol and turpentine (in that order) evaporate rapidly, and leave the pine resin in the wood. I rub off as much as I can of whatever is on the surface, and let it dry in the sun. Sometimes I have hung it up to dry indoors, but it does make the house smell of turpentine. My wife has very little sense of smell, and I don’t mind the smell, but others might, so I try to limit that sort of thing.

front with sealer

Front with sealer

 

Edge with sealer

Edge with sealer: notice the contrast between front and side. I hope to correct that, somewhat, with varnish.

 

Back with sealer.

Back with sealer. Still somewhat dull, but just wait until the varnishing begins!

 

hanging up to dry inside

Hanging up to dry inside.

 

Back drying inside

Back drying inside: I decided it was warm enough outside, so I moved it to the yard, and propped it in an old lawn chair.

 

Sealer drying in the sun:

Sealer drying in the sun: it was interesting to see that, as the wood warmed up, the sealer began to ooze back out of the pores, making tiny dots all over.

 

Varnish

Once the violin was very warm, and quite dry to the touch, I rubbed it down with a paper towel, to remove any residue, then coated the back with a yellow varnish, and the belly with a brown varnish. I hope to even out the color somewhat and diminish the sharp contrast between the dark, curly Koa and the nearly white Sitka Spruce.

First coat of varnish on the front

First coat of varnish on the front: makes quite a difference, doesn’t it?

 

one coat of varnish

There’s the whole fiddle in the sun, with one coat of varnish.

 

And...the back!

And…the back! Look how the curly Koa is catching the fire from the sun.

 

Koa Flame

Pretty serious flame in this curly koa wood! You can see why it was tough to carve.

 

Anyway, that is about as far as I expect to go, today. I may get another coat or two of varnish on there, this evening, but it will not be an appreciable visual difference until it is done. I expect to use at least another six coats before calling it complete.

Thanks for looking.

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