The bass bar in a violin-family instrument serves to support the bass-foot of the bridge, and the bass-side of the front plate (also called the “table” or, the “soundboard.”) Without adequate support in the proper place anong that side, the bass tones will sound quite flabby and unconvincing. The following is only a description of how I install the bass-bar, not telling anyone else how it ought to be done.
We always make the bass bar of European spruce, with the grain vertical to the plate; thus, flat-sawn to the bass-bar, itself. I begin by laying out two locations, one seventh of the distance from the center seam to the widest part of the bass-side edge at both upper and lower bout. That usually translates into about 15 mm off the center, at the widest point of the lower bout and 12 mm off center for the same place in the upper bout. I strike a line through those points , checking to see if it is far enough away from the inner eye of the bass-side f-hole to actually accommodate the completed bass-bar If it is not, then I move the line over a couple of millimeters, as needed, to gain clearance at the f-hole. Then I measure 40 mm inboard along the line from the upper and lower edges of the plate, to designate the end locations for the bass bar.
I cut the bass-bar blank to length, and plane it to the appropriate thickness, then hold it on the lines I have laid out, essentially perpendicular to what will be the plane of the ribs. I use a compass, set to the maximum gap at the bottom center of the bassbar, to scribe the contour of the plate onto each side of the bass bar. (Notice that, due to the compound curves of the violin plate, the two marks will not be the same. This is important.) Once I have both sides traced in accurately, I carve away the excess wood outside the line, to follow the line as closely as I can manage. I try to achieve a straight line between the two, regardless of where the two lines go, because that will follow the complex curves of the plate.
I double-check the bass-bar against the plate, and usually it is surprisingly close to fitting, at this point. So I use a strip of the paper-gauze tape available in pharmacies, about an inch wide, to cover the layout lines I had scribed into the plate, and then proceed to chalk-fit the bass-bar on top of that tape. The tape is very thin, so that I can see the lines through it (although I do trace them again onto the tape, to make them even easier to see.) But the tape is also so thin that, if I can get a perfect fit on the tape, when I remove the tape, I will have a perfect fit on the plate, as well, and no chalk residue to remove.
The hardest thing for me to learn in chalk-fitting, was to only remove the transferred chalk and the wood immediately under it, not the whole area. Frequently the culprit in an imperfect fit is actually quite a small area, so it is counter-productive to remove too much wood.
I chalk the tape, along the layout lines, and then press the bar into place, sliding it lengthwise a few milimeters back and forth to pick up some chalk;. I plane or scrape off the high spots where the chalk transferred, then try again. When I get a more or less full transfer of chalk from tape to bass-bar, I know the fit is acceptable. Then I carefully remove the tape, and (finally) glue and clamp the bar into place. Usually, I trim the bar a little, first, so it is nearly the correct shape on the top surface, so the clamps will fit more easily.
One bass bar is complete: the other has only been trimmed to make it easier to clamp.
After the glue has dried and the bar is rigidly secured, I use finger-planes to trim the bar to the size and shape I want.
Beginning with a medium-sized finger-plane.
Finishing with a small finger-plane.
Final touch-up with small plane and scrapers. The camera angle is what is making the two bars look so different.
Installing the top plates
So, the next task is to complete the inner edgework, and then install the top plates on the rib garlands. I plane a tiny bevel around the edge of the plate that will face the ribs; then file it to a curve, nearly quarter-round, flush with the outer rim of the plates. Then I position the plate on the garland as precisely as possible (sometimes things seem to have moved a bit, so I have to compromise a little.) Finally, I loosen a few of the spool clamps at a time and slip hot hide glue into the joint, using a thin palette knife. I clean up all around, so as to not leave glue on the outside of the violin.
Spool clamps can look like these, or even more simple: sections of closet rod with all-thread bolts. There are a lot of possible options.
Finally, the plate is fully glued and clamped, and I wait for it to dry.
Guarneri copy top plate installed with hot hide glue and spool clamps.
After the top plates are installed, I trace the European Maple back plates and cut them out. Here are the two garlands with the top plates installed and the back plates cut out:
Completed Garlands with plates.
Next stop will be arching the back plates.
Thanks for looking.
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I had a number of other projects going, so I neglected to maintain the website presence…the only post lately has been of another violin resurrection. But…I hope to change that.
The last post was of the neck-set on the 3/4 violin. It looked like this– but the back plate was not made, yet. Most makers complete the entire corpus, then set the neck. I complete the rib garland and the front plate, then set the neck while the inside mold is still in place. This allows me to get the neck-set perfect, and to level the back of the garland, including the back of the neck-heel, before making the plate. When I install the plate, it fits perfectly, only requiring the final trimming of the heel and button together, to establish the optimum height in the center of the curve of the heel.
Neck-set side view
Completing the Back Plate
So, the next thing was to trace the back plate, and complete it:
Corpus with back plate blank
Beginning to carve the back archings. There is a long way to go!
Once the arching is complete, I cut the purfling slot
Then I install the purfling, dry, to make sure everything fits correctly. That strip of aluminum is my bending strap.Then I glue the purfling in place.
Then I mark the edge of the crest, so I know where to carve the channel.
Then I carve the channel, using a gouge, and use planes and scrapers to fair-in the curves of the channel and the archings.
Here, the arching and purfling are complete…but the graduations (inside arching) are not begun.
Graduation
I begin by measuring the thicknesses all over the plate, so as not to run into any surprises and make the plate too thin. Then I use gouges and planes to bring all the thickness close to what I want. But, to make sure I don’t go too far, I measure and carve out small spots all over, to the exact thickness I want in each little “polka-dot”. That makes a “graduation map” that allows me to follow my plan to completion, by removing all the excess wood between the dots, thus “connecting the dots.”
There are other ways to do this. One involves a special tool, commonly called a “Strad-Spike”, because one was found among the tools of Antonio Stradivari. I have seen them and and have actually used them, but have never gotten around to building one. So…
Graduation map laid out.
Final thicknessing in progress.
Graduations almost completed.
By the way, I think it is interesting to hold the plates up to a lamp and see how much light comes through:
That is a lot of light coming through that spruce plate…it is about the thinnest plate I have made.
Even the maple lets a little light through.
Closing the Corpus
Finally, to install the label and close the corpus. (I always forget to take a picture of the label…sorry.) Most makers put their label in after everything is fully completed. I used to do that, but I found it so frustrating to get a glue-coated label through the f-hole, line it up correctly and get it smoothed out on the back plate…all working through the f-hole…that I decided my labels will go in when I close the corpus; always. That means the label predates the completion by a few weeks at most, as a rule. I think one time there was a long wait, but that was the lone exception.
Closing the corpus
Fully glued and clamped, using hot hide glue and spool-clamps.
Closed corpus from the back.
Closed corpus from the front. Dainty little thing, isn’t it? This is my first 3/4-size violin, and it feels pretty tiny.
Finishing
I removed the fingerboard so as to be able to easily access the entire exterior, for final scraping and finishing.
After that, I had a lot of “scraping and looking” to do. (Scrape and look, using a low-angle, dim light, then scrape and look some more.) When everything was as smooth as I could make it, and exactly the shape I wanted, I stained the entire violin with coffee, to get rid of the stark-white bare, new-wood look. It takes at least three coats, usually, to get the color dark enough that it will not shine through the varnish. The collateral effect is that the grain raises because of the water. So, I sand it lightly, to smooth the grain “just enough.” I want the grain to be visible in the final state, but not too visible.
Coffee stain
Then, I rubbed in a coat of the mineral ground. I brush it on liberally, rub it in hard, with my fingers, then wipe it off as hard as I can, using a rag. When it dries, the instrument will be whiter than ever– chalk-white, all over. The first time I did this I was pretty alarmed at the look, but I had just watched Roger Hargrave do the same thing, and knew that the white mineral would completely disappear with the first coat of sealer or varnish. And it did!
Here is the violin with the sealer applied:
With three coats of coffee, and the dark sealer, the wood looks pretty dark. But it will look good under the varnish.
The back, with the seal-coat.
After that it was a case of applying several coats of golden varnish, then a few coats of red-brown varnish, and a final two coats of the golden stuff.
Front varnish nearly complete
Back varnish nearly complete.
There is the front with the final coat of varnish.
Set-up
Standard set-up, and the violin will be done! That includes the saddle and endpin, as well as re-installing the fingerboard, fitting and installing pegs, a bridge, the nut, the soundpost, tailpiece, and strings. A chinrest completes the instrument.
Bottom of the violin before the endpin and saddle were installed.
Endpin installed: saddle is next.
Heres the plan: a rounded saddle to prevent “saddle cracks”. They work because there is no sharp corner to act s a stress riser.
There’s the footprint of the saddle: no further shaping is done until I cut out the mortise in the front plate.
I traced the footprint onto the front plate, and began cutting out the mortise.
Then I cut out the mortise using sharp gouges and a small knife. Any nicks in the varnish will be retouched later.
The varying thicknesses of the top plate can then be traced onto the saddle itself, and final shaping can begin.
Saddle and endpin are nearly complete. The saddle will be filed a little more, and the varnish retouch will happen later on.
I reinstalled the fingerboard, and while the glue is drying, I fit and installed the tuning pegs.
Fingerboard and pegs complete. Notice the nut is also intalled.
Completion
Finally the little violin is complete!
Front view of completed 3/4-size violin
Side view…
And the back view.
Close-up of the scroll
Thanks for looking. Please keep in mind that the Marylhurst Musical Instrument Show will be April 29th and 3oth. If you can make it, I hope to see you there. This little violin will be there for you to test drive, along with others.
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So, I went ahead and cut out those f-holes, using an f-hole “drill” my children bought for me, and an X-acto knife.
F-holes cut out and ready for the bassbar…outside view. They still will require a good deal of refinement.
Then I chalk-fit a bassbar blank, and glued it in place, using special clamps made by Jake Jelley, the friend who encouraged me to continue building instruments.
Bassbar blank with clamps. You can see the f-holes cut out…they still need more trimming.
Shaping the Bassbar
I carved and planed and scraped the bassbar into what I judged to be an appropriate shape for this instrument. Both it and the f-holes will receive a bit more scraping and shaping before they are varnished. The whole instrument, actually, is fair game for tweaking, refining, and perfecting, until the varnishing begins.
F-holes, bassbar and graduations nearly complete. Outer edges have been rounded to approximate their final shape.
Installing the Front Plate
I aligned the front plate as closely as I could with the rib garland, and applied six spool clamps–one for each inner block. Then I loosened one clamp at a time, and, using a thin palette knife, I slipped hot hide glue between the plate and the blocks and linings. I rinsed the edge, overhang and rib quickly with hot water, and wiped it with a rag, then re-tightened the clamp, and added more clamps between that clamp and the next, repeating the procedure untill all the edges and especially all the blocks were securely glued and clamped, and relatively clean.
Front plate installed, using spool clamps. Ann thinks these look like hair-curlers. 🙂
Back view of mold with front plate installed, and spool clamps. The mold will be removed after the neck is set.
Purfling Comes Next
Not everyone does things in the same order. I have had trouble, in the past, getting my edge overhangs even all the way around. If I install the purfling first, then I am locked in, so to speak, and if the overhang is uneven, there is nothing much I can do. But if I purfle after installing the plate, I can take time first to adjust that overhang, using files and scrapers, until I am satisfied that it is the way I want it, and then purfle, following my adjusted edge shape.
Installed front plate, from the mold side, showing the overhang. Notice that there are no back linings, yet.
Purfling laid out and lightly incised. (The shadow is my head– I was too close to the plate.)
The idea at this point is to just deepen the lines a bit, not to try to cut the full depth of the purfling slot. You can see that, in some places, the waste wood begins to pop out on its own. Most will have to be removed using a purfling pick. Here is a closer photo of the incised purfling lines:
Close-up of the incised purfling lines. That corner will still undergo significant shaping and refining.
So…next time, I will show the completed purfling, and the neck-set– I hope. 🙂
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The 14-inch Viola is getting closer to completion!
When I last posted, the viola was still in the spool clamps. The back plate was installed, but that was as far as I got that night.
Lots of promise, but not much “grace” in this picture.
Spool Clamps Off: Lots of Work to Do, Preparing for Purfling
So…the next step was to remove those clamps, adjust the overhangs as needed, and get on with the purfling. That sounds pretty straightforward, but there is always more to anything than meets the eye.
Looks nice, at first glance, but take a look at the neck button (where the back plate overlaps the heel of the neck.)
Side view of the same state of the viola.
Back view: button hidden by my hand. No purfling, and no shaping done.
Purfling Groove
I marked the purfling groove, using what is frequently called a “Purfling cutter“, but which is actually a marker. It has two blades that simply lay out the sides of the groove, by scribing them a set distance in from the outer edge…which is why I want the outer edge perfect, before beginning purfling. I have modified my cutter a bit, to make it work more reliably, but the link above shows the type of tool I use. I don’t think I have that brand. I can only use the marker to get within an inch or so of the corners. I lay out the corners by hand, sometimes using a frnch curve to achieve some repeatability.
Afterlaying out the groove in pencil and scribe marks, I incise the lines with a small sharp knife, then pick the waste wood from between the cuts.
Here is the completed groove:
Purfling groove complete. Notice that the button is taking shape as well. The neck, too is getting slimmer, and smoother. Lotsa work…
Here is a detail shot of the groove:
Detail of the purfling groove.
The Purfling, the Channel, and the Finish Work.
Finally I can start cutting and installing the purfling itself. I use a wood purfling, which is very brittle when dry, but bends nicely with a little moisture and a lot of heat. Once the purfling fits correctly, I lift each stip out partway, and insert hot hide glue under it, then force the strip back into the groove. Afterward, I mark the crest of the channel, and cut the channel using a sharp gouge. Finally, I use a tiny plane as well as gouges and scrapers to bring the convex curve of the plate into a fair, smooth agreement with the concave curve of the channel.
The purfling is complete, the channel is cut, and the back curve faired into the channel.
Purfling detail: look closely, and you can see the edge-crest line in pencil.
It is a fairly high-ribbed viola: 35mm. I think it will sound good.
And, it is looking more and more like a viola!
On the Home Stretch!
What is next? Edgework, and final scraping; coffee stain, mineral ground, sealer, and varnish…and then fittings and set-up. (The outer edgework is not even begun on the back plate.)
This is definitely as far as I am going tonight, though…. Getting too tired.
Thanks for looking
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As I work by myself, I frequently fail to take pictures. I did take a few, though. (If you are impatient, you can scroll down and peek at them.)
F-holes Cut Out
I used a special tool to begin the cutting out progress: It is called an “f-hole drill”, but all it really amounts to is a specialized twin-blade hole-cutter. My children bought it for me, one year, and it has been a wonderful tool. In the first place, obviously, it is a time saver, but the biggest difference is that I can now make the upper and lower eyes of my f-holes perfectly round, to begin with, and work any special shaping in, starting from the already round holes.
I remove the waste wood from the uprights of my f-holes with a small sharp knife—many makers use a saw, and I have done so as well, but I eventually reverted to the knife. Just personal preference, I suppose.
Bass Bar
Once the f-holes are cut out and close to perfect (always allowing for later nit-picking), I install the bass bar. The bass bar is a gently-arched brace supporting the bass-side foot of the bridge. Guitars have a whole collection of similar bracing, supporting what amounts to a nearly flat (and very thin) plate. The violin family instruments depend primarily upon the compound curves of the arching to supply strength, and only need the one brace to support the bass-side bridge-foot. The other side of the bridge is supported by the soundpost, which, while it is not directly under the treble-side bridge-foot, it is very close to it, and is in a location on the treble side matching the lateral position of the bass-bar on the bass side.
I lay out the position of the bass-bar, and then use a compass to transfer the shape of the inside of the front plate to the bass-bar blank. Then I use a knife to remove most of the waste-wood, and begin checking the results against the inside curve of the front plate. When the fit is getting close to correct…close enough that it is becoming difficult to see what needs to change…I apply a strip of paper-gauze adhesive tape (available in pharmacies) to the inside of the plate, covering the bass-bar position, and I rub blue chalk into the tape. I happen to use a product sold as “sidewalk chalk;” they are big sticks of chalk, and supposedly are easy to wash off of sidewalks. But they work well for me, and the blue is high-enough contrast that I can see it easily.
I press the nearly correctly-shaped bass-bar into the chalked tape, and check to see where the chalk transferred. I cut, plane or scrape just the chalked places from the bass-bar, repeating until, finally, when I press the bar into the tape, the whole thing comes up lightly coated with chalk. Then I remove the tape, clean off any remaining chalk from both pieces of wood, and install the bass-bar, using hot hide glue and clamps. I have a specialized set of wooden clamps made for this task.
When the bass bar glue is completely dry, I remove the clamps and trim the bar to the desired shape. I make my bars a little higher than most luthiers do, in the center, but tapering to about 5-6mm high for the last few centimeters of both ends. (I will take some pictures after I remove the inside mold, so you can see the final shape.)
Edge Preparation
It is much easier to do the inside edge-work if I do it before I install the plate on the garland. So, I use a tiny finger-plane, along with round and flat files, to round the inner edge of the plate, all the way around the perimeter. I may have to do a little correction later, but I want it as close to perfect as is possible, before gluing the plate to the garland.
Installing the Front Plate
I line up the plate on the garland as accurately as I can, matching the center-line of the plate to the centerline of the garland, and then use spool-clamps to hold it in place. I was originally taught to use tiny pins to assure good placement, but eventually discontinued the practice. We know for a fact that the old masters did this, as we can see the remnants of those wooden pins in their violins, still today. Perhaps I will eventually resume using pins. For now, I do not.
Once I have the plate perfectly aligned and securely clamped, using a very thin palette knife, I slip hot hide-glue into the joint between plate and garland, and then add more spool clamps to draw the joint closed. This is a very “stress-free” way to glue plates in place. I used to experience near-panic every time I installed a plate, racing to clamp the joint before the glue gelled, but now it is a very easy and relaxed task.
Purfling
As you may remember, I have not yet installed the purfling. I wait until the plate is on the garland before purfling nowadays, because the purfling “locks-in” the location of the plate edge, and I have had problems in the past with the rib garland changing shape a little, between my tracing the plate and trying to install it. so, after gluing the plate to the garland, the first step is to double check my over-hangs, to see that they are all pretty close to the same. If I need to change them, I do so: I am free to adjust the shape of the plate to match the garland again. When the overhangs are all acceptable, I begin purfling.
Purfling is fairly simple-sounding:
mark the groove location
cut the groove,
fit the purfling,
glue the purfling,
mark the edge crest, and
cut the channel.
It sounds easy, but I still find it a hard job to do perfectly. I want my miters perfect, my bee-stings clean and sharp, and all my borders parallel. This is my 30th instrument from scratch, and I am still finding it to be challenging. Guess I am a slow learner. 🙂
Cutting the Channel
Before I begin cutting the channel I use a compass to mark a line all the way around the instrument, 1.6 mm in from the outer edge. Then, using a sharp, curved gouge, I cut my channel to that edge crest line, trying to cut the whole channel to intersect the surface of the purfling and that pencil line.
Fairing in the Channel to the Arching
Once I have the purfling completed and the channel cut, I still have to fair-in the surface of the rest of the plate to match the curvature of the channel. I do not want there to be any sudden changes; humps and hollows catch the eye of the person looking, and call into question the skill of the maker. (Besides, I think they are ugly….) I use a very sharp finger-plane to begin shaping the surface of the plate and approximating the final curves I want. Finally I use sharp scrapers to bring the curvature of the whole plate to its final shape. I use a low-angle light to cast shadows from any humps or hollows, so that I can spot them and scrape them away. At this point, the scraper has to be sharp, and I have to use a gentle touch. The changes I am making are frequently much thinner than a piece of paper.
Outer Edgework
After the whole plate is the shape I want, the last task is to shape the outer edge. I begin by using a tiny finger-plane to take the outer corners down at a 45 degree angle, then use half-round files to shape the edge all the way around, bringing the curve of the outer edge up to just intersect the edge-crest line I established earlier. I get it as smooth and even as I can, using a file, but I know when I stain the wood with coffee, it will raise the grain terribly along these edges, so I will eventually re-smooth all of them, using abrasive paper of some sort. In this particular case, I did the outer edgework after setting the neck. No special reason…that is just what I did.
Neck Set
I measure carefully, and cut the tapered mortise using a razor-saw, then use a sharp chisel to remove the waste wood of the mortise. If I do the job correctly, it works very well. I check the sides and bottom to the mortise to see that they are flat and straight, then begin attempting to fit the neck. I have already joined the fingerboard to the neck and have shaped the heel where it will join the neck-block. So, from this point forward, all the shaping and adjustment will be done to the mortise, not the neck. When I am satisfied that the fit is correct, the neck will have to be centered. straight with the centerline of the front plate, straight with the centerline of the end block (not twisted at all), and at the correct angle to place the end of the fingerboard at the right height. Also, of course, the neck has to be set so that the distance from the nut to the edge of the front plate is correct. I check and re-check, until everything works correctly. Since I set the neck before installing the back plate, I want the heel of the neck to protrude past the back end of the neck-block. I will plane it flush after the glue is dry.
Here is the completed mortise, cut for the neck. The outer edgework has yet to be completed. You can see the edge-crest marks.
The mortise is complete, and I am ready to set the neck.
There is the dry-fit neck set. Notice the overhang of the heel of the neck beyond the neck-block. That will be planed off after the glue is dry.
So there is the dry-fit assembly. It is starting to look like a viola!
When every measurement is correct simultneously, and the fit is tight, I remove the neck one last time and slather hot hide glue into the neck mortise. Immediately I jam the neck into place, and quickly check all those measurements again. Bingo! They are all correct, and I can relax while the glue dries! Once the glue is dry, I plane off the neck heel overhang, flush with the neck-block.
The glue is dry, and the neck-heel overhang has been planed flush with the neck block. I am ready to remove the mold.
In this picture, I have filed the outer edge curvature already, and, though you can’t see it in this photo, I have also completed the graduations on the back plate, and have filed its inner edges, so it is ready to install. But; before I can do that, I have to remove the mold and add the back linings.
Ready to remove the mold.
Dreaming of the next step!
I am getting tired, though, and have some other things that need doing, so the viola will have to wait until another day to move any further toward completion.
Thanks for looking.
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I used to be terribly stressed, whenever installing plates– even violin plates. Now I clamp the dry plate in place with spool clamps, then, beginning with the corner blocks and C-bout ribs, I remove a few clamps and use a palette knife to insert glue before brushing the outside of the joint clean with hot water, and replacing the spool clamps. In this way, I can get the whole job done very quickly, and with no fuss.
Outside view of installed front cello plate.
Error!
The fact is, as you see it, it looks as if everything is fine. The next photo shows what I did wrong, though. If you look closely, you can see that I forgot to remove the front plate of the mold before installing the front plate of the Cello.
Forgot to remove front mold-plate before installing front cello plate. 🙁
So…it is a good thing I now install plates in such a stress-free way. Sure, it was disgusting to have forgotten such an important step. But it only required a few minutes with a heat gun to remove the front cello plate, as the glue was quite fresh when I realized my error. And, after using my handy electric screwdriver to remove all the screws, I slipped the mold-plate halves out and set them aside, and immediately re-installed the front cello plate.
So, what’s next?
I need to finish the scroll, now, and install the fingerboard. I like to set the neck while the cello corpus is still on the mold, so that, once everything is correct, and the neck is glued in place, I can simply plane the heel flush with the back side of the ribs, and install the back plate. (Yes, I will remember to remove the rest of the mold first! … and clean up the interior, etc….) 🙂
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