When I last posted, I had flattened the back plate, using a plane, but the shape was still oversized.
Flattened back plate for 5-string double bass.
So I traced out the plate shape using a small section of plastic pipe as a guide, and a ball-point pen inside the pipe to make the mark. Then I cut out the plate using my very old Craftsman “Auto-Scroller” saber saw.
My beloved wife, Ann, bought me this saw when we had been married for less than two years, and it has served me well for the last 38 years, but this may be the final plate it will cut out. It overheated rather badly during the cut. 🙁
Back Plate traced and cut to shape.
Once the plate was cut out, I used my curved-sole scrub-plane to remove waste wood, and rapidly bring the plate to near the proper thickness around the edge. As the thickness gets close to the target dimension, I switch over to the Ibex Finger-plane with the toothed blade and the wooden handle, to complete the thicknessing of the plate edge. The Oregon Big Leaf Maple is much more difficult to carve than the Spruce was, both because it is harder, and because the grain is highly flamed, meaning that it changes directions every centimeter or so, resisting all efforts to smoothly plane off the wood. The toothed plane helps, but when I start getting close to the right thickness, I will have to switch over to a scraper before the tear-outs from planing are too deep to be removed.
Arching of the back plate is underway.
You can see the longitudinal arching template in the above photo: it is just a thin piece of plywood with an 11′-3″ radius circle section cut out of it so as to leave the correct arching height in the center. I used that to help me establish the longitudinal arching. The Ibex plane is on the plate, and the scrub-plane is almost out of sight behind a small block-plane in the background. The small block-plane is helpful for smoothing the ridges left by the scrub-plane.
I am working to the rough sketch I made before beginning, with the plan for the back arching: (I did change the plan a little. I realized that I could extend the arching a little further “north,” as I have tapered the entire garland a little, so that the bend in the upper bouts will not be so severe, and the arching may be able to follow it a little way before flattening out to avoid the compound curve. It’s worth a try, anyway, and will not hurt anything.)
Rough sketch of arching-plan for the back plate.
Arching of the back-plate still in progress. Scrub-plane is more visible in this picture.
My hands and shoulders were getting too tired, so I went inside and used small finger-planes, files, and scrapers to refine the scroll. I am waiting on an order of carbon-fiber reinforcement materials to complete the neck, but other than that, I am pleased with how it is turning out.
Scroll is nearing completion.
I also completed the scraping of the Sitka Spruce belly, and it is pretty much ready to be glued to the garland.
Front plate and Garland, ready to be joined.
I pretty much wore myself out on this stretch: I’m looking like a tired old man, here. And I thought I was smiling…
The luthier with five-string double bass in progress.
As I said in the post regarding tools, I built the little curved-sole scrub-plane with the specific intent of using it to carve out the inside of the Sitka Spruce front plate for this Five-string Double Bass.
Rough-carving the interior, using the scrub plane.
Carving Dots
As the depth approached the correct value, I began switching over to the palm plane, there in the foreground. But as it turned out, I actually had a long way to go before I was anywhere near too thin.
I used the bass caliper to register thicknesses all over the plate, and then began carving “dots” at each location, to the desired thickness.
Carving “dots” of correct thicknesses all over the plate.
As I found (or created) spots that were at the correct thickness, I wrote in the thickness, and highlighted them in yellow, to warn myself against going any deeper. Eventually, I had mapped out the entire plate at least approximately according to this diagram from Peter Chandler’s book “So you want to build a Double Bass”:
Graduation map from Peter Chandler.
He had derived these measurements from a fine old master bass by Domenico Busan, which conveniently happened to be disassembled for repairs and restoration. He said that he had subsequently used these values on all his basses, and it always worked well. (Sounds good to me!)
I kept carving until I had “dots” all over the plate.
Thicknessing Dots completed.
Connecting the Dots
Then I began “Connecting the Dots”:
Connecting the dots.
As I planed away the excess wood, the “dots” got smaller and smaller, and, in some areas disappeared. By that point I had switched over to the palm plane which is less aggressive and makes a smoother surface.
Planing with the Palm Plane.
But eventually, it was pretty much all done, and time to cut out the f-holes. However, I decided to install the purfling first, and then cut out the f-holes.
Purfling installed:
I did not take pictures while this step was in progress: I just got going and pressed on until the job was finished, then took a few pictures. Sorry. I don’t always think about pictures.
I used this old purfling marker to trace my lines, then a thin-bladed knife to slice along the lines to make a slot…then picked out the waste wood and inlaid the purfling.
Old purfling tool: missing part replaced with maple.
Upper bouts with purfling installed.
Bass F-hole incised and center-bout with purfling.
Cutting the F-holes
I used a coping saw to cut out the f-holes. It was slow and laborious but it worked, and there was little chance of any catastrophic errors. The result was two f-holes cut within a millimeter of the line and no errors. It is starting to look like a double bass!
F-holes cut out.
Rough-cut f-hole ready for refinement.
Using a knife to refine the f-holes. ( I will finish them with a file.)
Bass-bar fitting
Fitting fixtures for fitting the Sitka Spruce bass-bar.
I use a very thin paper gauze tape for chalk-fitting bass-bars.
This is the tape I use, along with sidewalk chalk.
Paper tape with chalk applied.
The trick is to press the bar into the chalked tape, and “wiggle it” slightly, to pick up chalk on the high spots. then plane off just the chalked places and do it again, until all of the bass-bar comes up with chalk on it. That achieves a perfect fit. When the tape is finally removed, it takes all the chalk with it.
Then I warm the wood using a heat gun, apply a liberal coating of hot hide glue to both surfaces and clamp the bar in place. I leave it overnight to dry, just to make certain it will not pop back off (I have had it happen.)
Bass bar fitted, glued and clamped.
Installed bass-bar, ready to carve to shape.
The properly-installed bass-bar still has to be carved to the appropriate shape. I use planes to accomplish the carving.
Beginning to carve the bass-bar.
Bass bar nearly complete.
Bass bar complete
Interior of completed Front plate sitting on the garland.
Completed front plate resting on the garland. (Starting to look like a double bass!)
Back Plate Vision
There is still a good deal to be done, before I can install the Front plate, so I am stopping there for the time being.
But I really wanted to get a foretaste of what the Big Leaf maple of the back is going to look like; so I planed the inside and outside of the back plate flat, just to have a look at it:
Back plate inside surface.
Back plate outside surface.
It is pretty stuff! I am really looking forward to seeing it completed.
An elderly couple of friends gave me a large pile of highly flamed “fiddleback” maple, hoping I could build fiddles of the wood. This was Big Leaf Maple wood that the woman’s father had salvaged specifically because of the beautiful grain, perhaps fifty years ago, while making wood to heat his home.
Unfortunately, the wood turned out to be riddled with worm damage so that most of it is unusable. I felt bad about it, because she had hoped, all through the years, to have a box or something made of the wood, and now it seemed to be lost.
I had just repaired my bandsaw, though, while in the process of building the five-string double bass, and was busy cutting up billets of violin-wood to see what I really had that would be useable. I salvaged a few pieces of their maple wood that (maybe) could make a violin, and enough thin slices that I thought I would try a box for her.
When most people think of a box, they are thinking of a rectangular enclosure of some sort: but, I’m a violin maker! So…I bent the wood into an oval, and went from there:
There was not enough solid wood to do very much, so the heavier sections are from a different tree; one cut from the yard of my wife’s family home.
Gift box showing bent body, inlaid top, solid base and lid.
I inlaid the fiddleback maple section about 3 mm thick, into the lid which was also flamed maple, but not as spectacular. I trimmed it with purfling left over from the building of the five-string double bass.
The sides were only a little over a millimeter thick and bent around a hot iron made for that purpose. But they would be too fragile, if that was all that was there, and there would also be no secure way to fasten them to the base. So there is a 4 mm raised section glued to the base and the sides wrap around that “plug.” I added a 5 mm thick ring around the top, the same size as the bottom plug, in order to reinforce the upper edge.
Then I inlaid a 7 mm wide by 2 mm thick band of bent willow wood into the lid, positioned so that it fits cleanly inside the upper ring. As it happens, the lid fits perfectly in one direction, but if you turn it 180 degrees, it is very loose. So I stamped my name in the base and the lid: when you open the lid, if both are readable or if both are upside down, then the lid will fit.
Interior of bentwood box.
I varnished the bentwood box pretty much the same as I do my violins, and delivered it the following Saturday.
Both the husband and wife seemed quite pleased, so I am happy too.
As I was ready to begin the inside carving of the front plate, I realized that the little caliper I use for graduating violins and violas was simply not going to serve. I had a much larger caliper I had built 13 or 14 years ago, when I built my first bass, but it had been hanging in my workshop untouched for all those years and I was afraid that the battery might have corroded and ruined the digital indicator.
I had purchased the electronic tool from Harbor Freight, back in 2006 for about $10 (If I remember correctly,) and built the caliper out of hardware from a local outlet and a scrap of 1″ plywood decking. It was pretty crude, but it worked and was quite accurate.
Bass caliper, hanging amongst molds and templates.
I took out the little “battery-tray” thing, to see if my fears were justified, and it seemed as though the battery had not leaked, but was simply dead. So I went and bought a new battery, inserted it, and “Hey! It works!”
Bass Caliper with large display.
One of the things I like about the tool is that I can actually read the display. My small caliper has such a tiny display that I have difficulty reading it. Notice that it is reading .03 mm when it is not in use. The plywood flexes that much, under the weight of the lower jaw, so I hold the instrument upright and level, and press the “zero” function. Then it reads “zero” when it is held upright, and .03 mm when it is lying flat on its side.
So that was the first tool I was concerned about. The next concern was that I really did not want to gouge out the interior with mallet and gouges, as I had done the exterior. I was fearful of cutting too deep. So, in my mind, a “scrub-plane” with a curved sole was in order.
Curved-sole Scrub-plane
This also was one I began years ago, but did not complete soon enough to use it on the bass, nor even the cellos I made later, so the pieces languished in my toolbox drawer, waiting for me to finish the job.
I had made the body by welding together a slice of scrap stainless steel pipe, and some mild steel plate, along with a little section of angle iron and a 1/4″ pin. The cap iron was a shorter section of the same slice of stainless pipe, and the blade was (if I remember correctly) a piece of A1 tool steel. I had even gone so far as to cut sections of curly maple for handles, but had stopped there, and all the pieces were together in the toolbox. So– the time had come!
Pieces of the curved-sole scrub-plane.
Bottom view of Curved-sole Scrub-plane.
Partially assembled plane.
Completed Curved-Sole Scrub-Plane.
The completed plane, after a little adjusting, worked very well, and fit my hands comfortably, so the task of carving the inside of the bass front plate went very well.
Carving the inside of the Double Bass front plate using the Curved-sole Scrub-plane.
The only fault in the scrub-plane, because of the deeply curved sole, is that it tends to leave a rather un-smooth surface– like ruts in a dirt road. So, as I got closer to the desired thickness of the plate I was going to need a plane with a much less aggressive curved sole, and broader, as well, to produce a smooth surface.
Palm Plane
Fortunately, this one, I had built during my first bass-build, though it had not seen much use, as I never really got it adjusted right, and was busy enough that I just set it aside and completed the first bass using other tools. I got it back out and carefully sharpened the blade and adjusted the depth of the cut, and it turned out to work splendidly, though it took a little practice to get the angle in my grip just right.
Steel Palm Plane.
Steel Palm plane with a wooden finger plane.
All of the planes I have built work on the same principle: a blade is fixed at a given angle, and clamped in place by means of a cap-iron that slides under a transverse pin, and a screw that wedges the cap-iron between the pin and the blade. The principle is very old, and works well. It is used in many commercial planes, and predates all the companies that use it.
This little wooden plane was the first one I ever made. It is made of Padauk wood and is pretty crude, but it works well. (Ibex planes work better, but at the time I made it I had no money for an Ibex plane.)
Wooden plane disassembled. The thin end of the cap iron slides under the pin.
It is not a really tiny plane, but it fits my thumb and forefinger pretty comfortably. The blade was a section of scraper blade, and, while it works, I think I could improve it with a better choice of steel.
Wooden plane showing interior and relative size.
Assembled Padauk-wood plane.
Other Tools
The other tools (below) I had made years ago, and have been using regularly.
Homemade knives from an old sawzall blade.
Homemade gouges, forged from plow-steel or drill rod.
Many of my other tools are homemade, too– spool-clamps, scrapers, work cradles, templates and molds are all hand-made originals, as well as my workbench (which is usually buried in tools and materials…sorry).
So…that’s how I acquire tools! 🙂
Rationale
You might ask, “Why would you go to all that trouble when you can buy professional-level tools for reasonable prices?” The answer is two-fold:
In the first place, I really enjoy making tools! And then, there is a special joy in finding that the tools I make usually work very well, so I then have the pleasant experience of making musical instruments using the tools I made.
But the second reason is financial in nature: I simply did not have the extra money to buy every tool I needed when I began building instruments. But one does not haveto expend a great deal of cash, to get started in a craft, if one is willing to think, read, and learn the skills to make tools.
The time I spend building a tool is repaid many times over, by the pleasure I get in using the tool and the fact that all these tools will be used for many years to come, as I continue to build instruments. Are there sometimes failures? Once in a while an idea doesn’t work as well as I expected, but usually I find it very rewarding to make my own tools.
So, when I saw that there were two sections of “scrap” left over, near where the neck end of the five-string double bass back was cut out, I realized that a 5-string fiddle back could fit into each of those two pieces.
So, I salvaged the wood, and not only got two backs, but also the neck blanks for two 5-string fiddles.
Five-string fiddle back cut from the scrap left from a 5-string double bass back.
Arching the Plate
Five string fiddle begun, with back and neck from scrap from a 5-string double bass back.
I really like the look of the Oregon Big Leaf Maple back wood. I enjoyed arching the plate.
Five-string fiddle back arching nearly complete. It is sitting on the five-string double bass garland whose back provided the scrap for the fiddle-back.
Purfling the Plate
On all my five-string instruments I usually include a purfling weave. It is a modified fleur-de-lis I designed for my first five-string fiddle and have continued to use on subsequent work.
Five-string fiddle back with purfling slots incised and ready to complete.
In this photo, the slots for the purfling have been incised, but not cut deeply, so the next step is to slice deeply enough that the waste wood can be removed from between the cuts, and the purfling strips inlaid in the resulting slot.
I will include the purfling process in subsequent posts.
When I last posted, I had the garland pretty much complete, and the materials were prepared for the neck and the front and back plates. I had cut the back plate roughly to shape, in order to use as much of the “fall-off” material from the back plates, as possible, from which to make the neck.
I went ahead with the neck and scroll, just because I find it encouraging to have some of the “pretty” work done, as it makes me feel that I am making progress. You can see the neck progress, here.
But at some point, one has to go ahead with the task of bookmatching the plates and getting them ready to carve.
Sitka Spruce front plate halves for the five-string double bass.Rough shape of the five-string double bass back plate, with the template for the neck. The neck was cut out of the scrap from the back.
So, for the front and back plates, the next thing on the agenda was to plane the center-joints absolutely flat and straight and then glue them together. It took two tries on each of them, as it turned out that while they were technically “straight”, and if I put a try-square at any given point, they seemed to be square…in reality, there was a longitudinal twist to the surface I had planed, and the fit was not acceptable. (sigh…) No big deal… I just had to saw the joint back apart, and try again.
Finally, I got everything lined up correctly; then I glued and clamped the plate halves together, and produced the plate banks, ready to trace the actual shapes.
Sitka spruce front plate for five-string double bass, bookmatched, and ready to glue.
Front and back plates, bookmatched, and ready to trace shapes.
Tracing the plates
Sitka spruce front plate, ready to trace the shape.
Ready to trace the shape of the garland onto the front plate.
Using a pipe spacer to trace the shape of the garland onto the Front plate.
Tracing the plate out with a pipe spacer like that enables me to establish a very even overhang of about 4.5 mm. The problem is, it also makes round corners, which I did not want. So I had to correct, the corners, using a long straightedge to “point” the corners toward the center of the plate at the far end, and then use circle templates to extend the curvature of the plate edge above and below the corner to meet the straight lines. (Incidentally, the reason I have stopped using a washer for a spacer, is that any washer small enough to have the right distance from outside to inside also is so thin that if there is the smallest change in the fit between the plate and the garland, the washer will slide under the garland, changing the overhang distance to zero. The thin slice of PVC pipe never does that.)
Cutting out the Front Plate
I used an old Craftsman “Auto-scroller” saber-saw (Hand-held jigsaw) to cut out the perimeter of the front plate. Ann, my beloved wife, bought me that saw 36 years ago, when we had been married for only about three years. That little saw has a lot of miles on it!
Cutting out the completed shape of the front plate. I am not attempting to cut exactly to the lines. I will correct to the lines, after the arching has been completed.
Inside view: the cutting is complete: the front plate is ready for arching.
Outside view of the front plate.
Arching is Next:
Before I could begin arching, I needed to mark the intended plate thickness: I used a marking tool to scribe a line all the way around the plate at 6 mm. Before the plate is done, this will be reduced to 5 mm in most areas. I used a ballpoint pen to highlight the groove so that I could more easily see it when I am working, and not accidentally go past it.
Edge-thickness scribed into front plate.
Then I secured the plate in a cradle especially made to fit this design, and secured it in place by affixing small squares of 1/4″ plywood around the perimeter so that the plate will not shift laterally, while I am working on it. The reason the little stop-blocks are so thin is that I do not want them to be in the way when I am planing the edges.
Front plate secured in a work cradle.
Tools for arching: cradle, gouges and planes.
Sculpting the front plate arch.
Front plate arching in progress!
Planing the arching surface smooth.
Some of the planes used to shape the bass.
Shadow line defining the longitudinal arching shape.
Transverse arching shape.
Arching nearing completion.
Arching and outline completed.
Time to lay out the F-holes!
F-holes laid out, incised, and inked.
When I build the smaller instruments, I inside the f-hole perimeters quite deeply, knowing that, without exception, I end up needing to correct the arching, using the f-hole side-profile as a guide. I want the “stem” portion of the f-holes to be essentially parallel to the plane of the garland-plate joint when viewed from the side. On the violins and violas I have built, I have universally found that, in spite of my best intentions, I have left too much “puffiness” in the area of the lower wings of the f-holes and I need to plane away more wood. If I have incised them deeply enough, I don’t lose the marks when I remove the wood.
I was quite pleased to find that, on this instrument, the side profile was exactly what I had hoped for, as soon as I laid it out. So I incised them, but not very deeply, and then inked them with a ball-point pen, so that I could easily see them while perfecting the arching later, using a scraper.
So– the next step will be to complete the “graduation” of the plate– carving away the majority of the wood thickness from the inside of the plate, so that the plate is the correct thickness all over…ranging from 9mm at the center, all the way down to 5mm in the flanks.
All of the Big Leaf maple portions of this bass are made from a log I was given, years ago, by the late Terry Howell. The fellow I hired to mill it up said he did not know how to do quarter-sawing or flitch-sawing, so I settled for plane-sawing, which means that all I have is slabs. That is OK, because I like using slab-sawn wood, especially for backs; but it also meant I had no pieces thick enough for a neck on a bass. So…I chose to glue-laminate the neck billet, and produce a piece thick enough to use.
Contrary to my usual rule of “nothing but hot hide-glue,” I chose to use Titebond on this, reasoning that it is not supposed to ever come apart. One of the reasons we usually stick with hot hide glue is that it is always reversible. Titebond is not.) My son Brian lent me about a dozen clamps to make the job easier. He makes exquisite guitars, and learned early the value of having lots of clamps available.
Neck billet bookmatched, glued and clamped.
The resulting billet was still about 3/4″ too narrow to accommodate the “ears” of the scroll, so I added a layer on each side, carefully chosen from nearby grain, so they would match (hopefully), and not be too obtrusive.
Extra wood glued on for “ears.”
Carving the scroll
Finally, I drew in the planned shape of the entire scroll and pegbox, and proceeded to cut away as much waste-wood as possible, using a saw.
I forgot to photograph the initial carving portion, so this is from a five-string cello I made earlier. The same process is followed.
Saw-work on a viola scroll…I forgot to photograph this step on this bass.
Removing waste wood using gouges. (Again, this is a viola scroll; but the same principle applies.)
All saw-work is done on the scroll…time to remove wood using gouges and planes.
Removing waste wood using a gouge.
Removing waste wood using a palm-plane.
Waste wood has mostly been removed. Time to begin the pegbox and volute.
Carving the Pegbox
Pegbox has been drawn and is ready to carve.
Beginning the interior of the pegbox.
Pegbox carving is complete.
Carving the Volute
Beginning the volute for the 5-string double bass scroll.
Bass Scrolls are BIG!
That large viola scroll fits easily…loosely…inside the bass pegbox. Reminds me of a mother monkey cuddling her baby. The bass scroll is simply huge, compared to any other instrument I build. (No, I will never build an octobass.)
As you can see, there is a lot that goes into carving a scroll…and this thing is really big! So, though I’m not done, I will go ahead and post this, and share the rest as it gets done. (The turns of the scroll will be more deeply undercut, and all surfaces more refined.)
This is not really a new project, but rather one that was “tabled,” for lack of better term…work was suspended until a better set of circumstances emerged.
I built the mold for this bass in 2015, began bending ribs in 2017, with a woefully inadequate bending iron, and a great deal of frustration.
A commission came in, so I set aside the bass, to work on the cello, and never came back to it…so it sat in the corner of my workshop silently sneering at me every time I looked that way.
But! Since I was laid off from my job, where I had worked for 33-1/3 years, in January, I am catching up with some projects and able to face others with new eyes.
Here is the five-string 16-1/2″ viola I am just finishing up, balanced on top of the bass mold:
Large viola with double bass mold.
Once I had the bass mold up on my bench again, it was easier to confront the problems, rather than avoiding them.
The New Bending Iron
The first thing I needed was a new bending iron. A fellow I met online, John Koehler, a fellow bass maker, told me how he built his bending iron. So I followed his lead, and built a new bending iron:
My homemade bending iron.
It is a section of exhaust tube, welded to a piece of angle iron, so that I could clamp the apparatus in a vise. Heat is supplied by a 550-W electric charcoal briquette lighter, controlled by a 600-W dimmer switch. It took a little trial and error to get it set up correctly and to calibrate it, but it turned out to work very well! (What a relief!)
Bending the ribs
Bending the remaining two Big Leaf Maple ribs was nearly effortless, and took about ten minutes, tops, not counting waiting for the tube to heat up.
Lower ribs bent to approximate the mold shape.
Installing the ribs and linings
Then I glued the ribs into the fir blocks on the mold with hot hide glue, one at a time, and affixed the willow linings in the same manner before moving to the next rib.
Treble rib with linings installed.
Once one rib was completely secure, trimmed and lined, I rolled the bass mold over and repeated the operation on the other side.
Bass side rib with linings installed.
I planed the linings flush with the ribs and blocks, and the garland was essentially complete. It will require careful leveling before fitting the plates, but not much other than that.
Completed rib garland.
In the coming weeks, I will complete the center-joins of front and back plates, then complete the carving of the plates and the neck and scroll, and start putting this bass together!
Just as a teaser, this is the wood for the front, back and neck:
Sitka Spruce billet for the front plate.
Big Leaf Maple for the back plate and neck.
(Notice that there is a fair chunk left over where the neck pattern does not use all the wood it is on: watch that space! )
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.
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