Final woodwork on 5-string 16-1/2″ Viola

Last “woodwork” tasks:

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.
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.
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.
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.
I cut the center bout slots, first, along with the corners.

 

the goal is to complete the whole slot before inserting any purfling.
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.
Outer perimeter complete…working on the weaves.

 

Purfling weave nearly done. Notice that some joints are not as clean as others.
Purfling weave is nearly complete. Notice that some joints are not as clean as others.

 

Completed weave: needs to be planed flush.
Completed weave: needs to be planed flush.

 

Completed purfling weave...warts and all.
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 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
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.
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.
Front ready for varnish.

 

Side ready for varnish.
Side ready for varnish.

 

Back 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:

    1. a tanning treatment,
    2. a mineral ground treatment,
    3. a sealer, to lock the mineral ground in place, and
    4. finally, the varnish itself in a series of 6-12 coats, depending on color.

 

Enough for today.

 

Thanks for looking.

 

 

 

 

 

Scroll and Neck Carving

Carving the scroll

Beginning with the Saw

When I first tried making an instrument (a viola) I did not know about using a saw to start, and I carved the entire scroll by hand with a set of small gouges my wife had presented me with a few years earlier. That took a long time, and it was very difficult to keep symmetrical.

Later, I saw a series of photos posted by a maker in Brasil, who showed how he used a thin-bladed saw to outline the scroll, making many small cuts, then removing the waste wood with a combination of saw and gouges. That was a bit of a revelation, and I enthusiastically embraced the change. I did, however, take a bit of practice to master the concept.

So here is the process:

{You can see the dark lines and spots in the wood. This is called “spalting” and is very popular with some people, though it actually is caused by a fungus. This particular Big Leaf Maple billet, along with that of the back, was salvaged from an old tree taken down on my wife’s family’s property.)

First, I carefully laid out both sides of the scroll, then  I used my bandsaw to cut out the whole “footprint” of the scroll and neck.

Then I went back and laid out the volute, including the centerline, on the outside of the curve, all the way around, so I know what the scroll should look like from the front and back, as well as both sides. I also used a knife to scribe the centerline deeply enough that I will not lose it as I begin to shape the outside of the scroll.

Then I used the same bandsaw to remove the slabs from the sides of the pegbox, and a little way down into the neck: (You can see I already rounded the heel of the scroll a little, too, with a gouge. That is a personal quirk of mine…I want that heel looking “round” right from the beginning.)

Scroll with outline cut and slabs removed.
Scroll with outline cut and slabs removed.

 

Then I use a small pull-saw (Japanese style, but I don’t know what brand) to cut beside the scroll profile lines just down to where they nearly touch the sides of the volute lines around the outside of the scroll. It is very important to keep these cuts perpendicular to the centerline of the scroll.

Sawing to create the profile of the scroll.
Sawing to create the profile of the scroll.

 

Then I use a combination of a thin saw and various gouges to remove the waste wood created by the saw.

Removing waste wood.
Removing waste wood.

 

Continuing to remove waste wood.
Continuing to remove waste wood.

 

At some point (usually, the earlier the better) I will decide to carve out the interior of the pegbox. I did not take any photos of that process this time, but there are a variety of options. Some makers use a drill to carefully excavate a series of small holes, so that it is easier to remove the waste wood between the holes. That is practical, but you have to be very careful to not go too deep, or too far off to either side. (It is easy to destroy your scroll, in other words…)

I outlined the opening with a small straight chisel, then used that same chisel to begin excavating the waste wood from the interior of the pegbox. You can also see the remaining layout lines for the neck, in this photograph.

Carving the pegbox.
Carving the pegbox.

 

After the pegbox was mostly complete, I began carving the turns of the scroll, as well. This is another place where it is very easy to make serious errors. I continually examine the scroll from all angles to see to it that both sides are progressing equally, and that I am achieving a satisfactory symmetry. If I can keep the two sides looking like mirror images of one another up until the final smoothing, then there is little danger that the final smoothing will change that symmetry.

Beginning to carve the turns of the scroll.
Beginning to carve the turns of the scroll.

 

Continuing to carve pegbox and beginning to carve the scroll.
Continuing to carve the pegbox and the turns of the scroll.

 

Scroll nearly complete; Pegbox essentially complete.
Scroll nearly complete; Pegbox essentially complete.

 

Once the scroll and pegbox were complete, I prepared the fingerboard and glued it in place temporarily. I need the fingerboard installed, in order to correctly set the neck. (I realize that some makers can successfully set the neck without the fingerboard, and I have done so in the past, but it is also easy to make a mistake. I like having the fingerboard correct, and use it to help set the neck correctly.)

Scroll starting to look pretty close to complete: Fingerboard temporarily installed.
Scroll is complete: Fingerboard is temporarily installed.

Setting the Neck

(I did not take photos of this process, but it goes as follows:)

  1. Lay out the location and footprint of the neck mortise.
  2. Use a thin razor saw to cut the sides of the neck mortise, but not too deeply.
  3. Use very sharp chisels and gouges to remove the waste wood from within the mortise.
  4. Keep checking the fit and adjusting the mortise, until the neck fits perfectly.
  5. Glue the neck in place, using hot hide glue, and a clamp.
Neck properly set, glued and clamped. Glove is for padding.
Neck properly set, glued and clamped. Glove is for padding.

You can see in the above photograph that the neck heel has been left to be carved to the correct shape at the same time as the back button. (A lot of people do not realize that, in the violin-family instruments, the joint between the heel of the neck and the back button is critically important to the strength of the neck joint. It is not just to be pretty, as is sometimes the case in guitars.)

 

Neck-set back view, showing plastic clamp-pad.
Neck-set back view, showing plastic clamp-pad and spalted Big-Leaf Maple back.

 

After I carved the heel to the correct shape, The instrument was essentially done, and final shaping and scraping for varnish preparation is the next step.

Side view, showing completed neck-heel.
Side view, showing completed neck-heel.

 

Back view showing back button shape.
Back view showing back button shape.

 

Ready for final Varnish-prep.
Ready for final Varnish-prep.

 

I will save the varnishing process for the next post.

 

Thanks for looking.