Varnishing Process for the 16-1/2″ five-string Viola:
All Smoothing and Varnish-prep is done:
When I last posted, the final woodwork had been completed. I had twice wetted down the wood, to raise the grain, and scraped and sanded away the rough raised grain. The wood was stable enough to commence the tanning process.
After the wood is smooth, there will be:
a tanning treatment,
a mineral ground treatment,
a sealer, to lock the mineral ground in place, and
finally, the varnish itself in a series of 6-12 coats, depending on color.
Tanning the Wood
People who live in very sunny regions (New Mexico, for instance) need no light booth: they simply hang their instrument out in the sun for a few hours and it takes on a deep yellow-tan color. I live in Oregon. Western Oregon, between Portland and the coast. We are more likely to achieve a patina of bird-droppings than a sun-tan, if we hang instruments outdoors. (Sigh…)
So, a number of years ago, I bought an old cabinet, about seven feet tall, lined it with aluminum foil as a reflector, wired it with a strong UV source (two 48″ fluorescent UV tubes in a shop-light fixture), and I hang my instruments in it overnight. To heighten the effect, I brush on a coat of very diluted Sodium nitrite and let it dry before I expose it to the UV. This works pretty well, and I have pretty much adopted it as a normal pre-varnish treatment.
Tanned front side of the 16-1/2″ five-string Viola.
Tanned back side of the same instrument.
Mineral Ground:
Years ago, an excellent luthier in Europe posted a detailed explanation of why and how he employs a mineral ground in his instruments, to improve projection. I tried it (because, “if it is good enough for Roger Hargraves…”) and immediately started getting better reviews on the sound of my instruments.
So…obviously, that became part of my process, as well. I use gypsum powder, suspended in coffee (gotta wake up the tone!) so as to achieve a little deeper color in the same move. I rub it in vigorously, trying to get the particles of gypsum to actually penetrate the pores of the wood, then rub off the excess with a rag, before it is fully dry. When it is dry, it obscures the grain, and turns a chalky white color.
Mineral ground drying on 16-1/2″ 5-string Viola. (5-string bass beginning in background.)
Mineral Ground is dry. I will sand off any excess mineral, and then apply the sealer.
Sealer
Sealer coat, front view.
Sealer coat, back view.
The sealer, in this case, is simply rosin, dissolved in turpentine and alcohol. The mixture soaks into the wood, causing the mineral ground to become transparent, then the solvents evaporate, leaving the rosin in the wood. The mineral ground will never again be visible.
Varnish Beginning
When the sealer is dry, I sand lightly, using 320 grit, to remove any lumps I may not have seen, and then I am ready to begin varnishing. I always begin with two base-coats of very yellow/gold varnish, so that the gold color will shine through the darker color coats.
Two coats of yellow varnish, side and front view.
Two coats of yellow varnish, back view.
I like the way the European Maple and Spruce are shining through the varnish. I think they will sound great, too. Tapping on the corpus, it sounds as though it will have a big, deep voice.
I will follow the completion of the varnish process in a later post.
Last “woodwork” tasks on the 16-1/2″ five-string Viola:
Last time, we finished up with the neck set, and the corpus closed, but all the edgework (and final shaping of the neck heel, etc.) left to be done.
Closed corpus, purfling weave sketched, heel/button need carving.
Carving the heel/button combination
The neck heel and the back button, together, make up the majority of the strength of the neck-joint. I once had a cello come in for repair, fully up to tension, but “something was loose.” Yeah, the ONLY glue still holding in the neck-joint was the glue between the neck heel and back button! I removed the neck, cleaned out the old glue, and re-glued the entire joint: but I never forgot that the heel/button connection alone had held the entire load of the string tension! So I make certain that this joint is perfect, and the two are carved as one piece after gluing.
There is also a specific measurement from the center of the neck-heel curve to the top edge of each side of the front plate where it joins the back: in violas, I shoot for exactly 27mm.
Heel and button carved: ready to begin purfling. I have laid out the purfling and incised it.
Purfling
I used to struggle with cutting the purfling slot (I still do, but for different reasons) because I was trying to cut the full depth in a single pass, or maybe two. One of my teachers corrected me, saying that the first pass around, with the knife, is just to “darken the lines” left by the marker. Then it is relatively easy for the blade to follow the groove for subsequent fast passes, each making the slice a little deeper. Finally, I use a special tool to pick out the waste wood from between the lines.
Purfling-pick with front plate.
One problem I faced with the back plate that I had not noticed so much, on the front plate, even though it had the same issue: This purfling is a little wider than what I usually use, so, in spite of the fact that I marked out the correct width, my pick tools (all of them) are made for the narrower purfling, and they do not readily make the slot the correct width. That meant a lot of going back and widening things just a little bit (0.5 mm, usually.) The European spruce of the front plate is soft, and quite forgiving. The harder European maple back plate does not give at all, so if the slot is too narrow, the strip is not going in, at all.
Another issue is that the purfling weave is on top of a fairly thin portion of the back plate, so I could not cut my slots as deeply as I wanted to. Thus, there was very little wood-support for the purfling, and the pieces were difficult to fit, whereas, around the perimeter, I could cut a slot for the full depth of the purfling strips and achieve full support. Ah, well…that’s life. But there were some joints I am not so happy with.
Anyway, this is how the purfling went:
I cut the center bout slots, first, along with the corners.
The goal is to complete the whole slot before inserting any purfling. (Notice the shallow purfling-weave slots.)
Installing the purfling
As I did on the front plate, I installed the center-bout strips first, dry, and then the rest of the perimeter. I glued the perimeter in completely, before beginning the purfling weaves, themselves.
In the case of the purfling weaves, since the slots were so shallow, I glued each piece as I installed it, then worked on the other end of the instrument while the glue from that piece set up and began to hold.
Outer perimeter complete…working on the weaves.
Purfling weave is nearly complete. Notice that some joints are not as clean as others.
Completed purfling weave: still needs to be planed flush.
Completed purfling weave…”warts and all.” I may elect to go back and improve things a little. (Probably not.)The other weave turned out a little better.
The Channel
Once the purfling is all in place, and planed flush, it is time to carve the “channel.” This is a slight “ditch” that runs all the way around the perimeter: the bottom of the “ditch” is usually at the purfling, while the outer edge of the ditch ends exactly at a line called the “crest,” which is about 40% of the distance in, from the outer edge of the plate to the outer edge of the purfling. The inner edge of the “ditch” will be planed and scraped back to “fair” into the surface of the arching, without any lumps or hollows.
Notice the pencil-line “crest”, between the purfling and the plate-edge.
Edgework
Finally, after all the surface of the plate is correct, I plane, scrape and sand the edges themselves, so that the outer curve of the plate edge perfectly meets the inner curve of the channel, all the way around the plate.
In this case, I did not take the picture until after I had completed the next step, which was to wet the whole structure down with water, in order to deliberately raise the grain, so that any imperfections, or compressed areas, will rise up and be seen…and subsequently, be scraped and sanded flush again. All this to say, please understand the “rough” surface of all the wood.
Edgework complete, but still rough with raised grain.
So…that means the whole instrument is now complete, minus the varnish prep-work, and the actual varnish and set-up!
Front ready for varnish.
Side ready for varnish.
Back ready for varnish.
Varnish Sequence
I will post the varnish sequence as it occurs, but, for now, know that the sequence will include at least two “wet-it-down, let-it-dry, and scrape/sand-it-smooth” iterations. The idea is to produce a surface that will no longer respond to moisture by raising the grain. This is particularly important on the handle portion of the neck, where the moisture from players’ hands will certainly be in contact with the wood, every time the instrument is played. But, under the varnish, the slightest discontinuity will become glaringly obvious, so that is important as well.
After the wood is smooth, there will be:
a tanning treatment,
a mineral ground treatment,
a sealer, to lock the mineral ground in place, and
finally, the varnish itself in a series of 6-12 coats, depending on color.
The raw wood is quite porous, and would soak up varnish like a sponge…which would dampen the viola sound. So we don’t want that to happen! The solution to the problem seems to be to fill the pores of the wood with very fine particles of mineral of some sort. I don’t particularly want something that would form a concretion, as some makers have done, because I think that also changes the sound, but in a different way.
I used Gypsum, ground very fine in a mortar, then suspended in water, and daubed onto the surface; then vigorously rubbed into the pores. After rubbing the mineral into the entire surface (except the “handle” area of the neck) I used a damp cloth to rub all the excess gypsum back off. While it is wet, it just looks like wet wood, but as it dries, it turns chalk-white, assuring me that the surface is truly saturated with the particles.
Partially dry mineral ground, front side.
Partially dry mineral ground, back side.
Then, after the gypsum suspension is completely dry, I use fine sandpaper to remove any excess mineral from the surface, so that there are no thick patches of mineral.
Dry Mineral ground, rubbed clean.
Locking the mineral ground in the wood: Sealer
As you can see in the above photograph, the mineral isstill saturating the surface, and obscuring the grain. However, when I apply the sealer (in this case, a mixture of rosin, turpentine, and alcohol) the mineral ground will become completely transparent, and will permanently disappear. The varnish will then be free to show off the grain of the wood.
Front side with sealer.
Side with sealer.
Back with sealer.
Making it Shine: Beginning the varnish
It takes a while for the sealer to dry, because of the turpentine content, but as it dries, the alcohol evaporates first, then the turpentine, leaving the rosin in the wood (which is where rosin comes from in the first place, of course) locking the gypsum particles in place. and further sealing the wood against saturation with varnish.
Before proceeding to the varnish, I carefully sanded all over, to clean up any spots that still felt rough or sticky, then wiped the entire instrument down with alcohol to remove any rosin residue from the surface.
Then I applied a first coat of yellow varnish, as I have noticed that many of the old instruments seem to have something yellow under the darker red or brown varnish. You canespecially see it in the areas where the colored varnish has worn thin, or is completely gone. (Not all of them have this color, but I like it, so that is what I have chosen to do.)
So, here is the base coat of yellow varnish:
Base coat of yellow varnish on front side.
Base coat of yellow varnish on the side.
Base coat of yellow varnish on the back side. The grain of the spalted maple is showing better, again.
Base coat of yellow varnish on scroll and neck heel.
I do not apply varnish to the “handle” portion of the neck until everything else is completely done. After everything else is done, including set-up, I will rub down the handle area with 400-grit abrasive one last time, and then put about a dime-sized dot of shellac on a rag, on the end of my finger, and vigorously rub it into the wood of the handle area, until it is completely dry. This somewhat seals the wood against sweat and dirt, without leaving a heavy, “slick” coating that would cause drag on a player’s hand.
The rest of the varnish coats will be building color toward the final look of the instrument. I will include them in another post.
Varnish Progress on the Commissioned 5-String Fiddle
Varnish Procedure for All my Instruments:
Complete all scraping, shaping and smoothing: varnish preparation.
Wet the instrument down to raise the grain, then
Lightly sand with fine-grit abrasive, to remove rough bits of raised wood.
Rub in a mineral ground, then use a rag to remove excess.
After the ground dries, sand lightly again, to remove any rough excess mineral.
Seal using turpentine and rosin.
After the sealer is dry, begin adding coats of varnish.
Following the above format, here are the results:
Dried Mineral Ground, compared with varnished instruments.
Front view with sealer…mineral has disappeared.
Side view with sealer…the grain is visible; the ground is transparent.
Back with sealer; the grain is very visible, the ground has disappeared.
Now the varnishing begins!
The mineral ground was intended to close all the open pores in the wood so that the varnish will not saturate the wood. Then the sealer locks the mineral ground in place and causes it to become transparent. (Think “wet t-shirt material.” White stuff becomes transparent when wet, as a rule.)
So, now the varnish further seals the wood and begins to add gloss and protection from moisture, dirt, etc. And, if we do it correctly, it will add the color we want, as well, without losing transparency.
I have used both oil varnishes and spirit varnishes. I believe the old masters used oil varnish, but currently, I have moved to spirit varnish. Perhaps one day I will use oil varnishes again
Spirit varnish dries so rapidly that I can usually apply four coats of varnish the first day. So here is the fiddle with four coats of spirit varnish:
Front, with four coats varnish…still pretty yellow.
Bass side with four coats of varnish: Too much contrast between side and front plate.
Back plate with four coats of varnish… looking pretty nice!
Leveling the varnish
So, then, after the first few coats have dried hard, we sand lightly to remove brush marks, sags, drips, etc. and begin to add color coats. Usually, I have a pattern of shading I use, to emulate light “wear” patterns. This one has very little of that.
Final color front plate…the light patch on the upper left is a reflection.
Final color treble side: notice that the front and side match nicely, now.
Final color bass side.
Final color back plate.
Final color bass side scroll.
Final color treble side scroll.
Final Finish Work
So, now we will let the varnish thoroughly dry, and harden; after which there may be retouching and minor changes to make, but the main focus will become set-up after that. (In case anyone is interested, the customer has been kept abreast of every step in the build, and is getting quite anxious to take possession.) 🙂
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