Friday, November 21, 2008


As I wanted to try and do this build from scratch as much a s possible, I bought some bone for nuts and saddles on eBay a while back. The vendors description at the time was: "2 lbs of treated cattle bone for carving", with a photo of a number of bone pieces cut in half next to a ruler showing them at about 4" long, a little on the small side, but I hoped that with a bit of effort I should be able to get a fair amount of pieces cut from them. I got the lot for about $12 plus $8 for shipping. They arrived as described and everything was honky dory.

I had been following discussions and articles on the net about suitable material for nuts and saddles, and there seems to be many possibilities and options. From man made materials like Corian and Micarta, to wood, shell, bone, horn, tusk and even stone and metals. But most sources tooted bone as very suitable for the job, because of it's density, workability, look and price.

Over the summer I attended a serious of lectures at my work by a paleontologist called Stuart Sumida. It was an obvious opportunity to pick his brain. I showed him the bones I bought and told him what they were for. He guessed they might be phalanges - finger or toe bones.

I also asked him what bone was the densest you could find, to which he answered a Baculum or penis bone. Apparently, if an male breaks this bone, there is no way any female with just a little self respect would ever even consider a 'little bit of how's your farther' if that bone wasn't intact on the male, and if you believe in evolutionary theory that should have resulted in the development of a very dense and strong bone.

Just for fun I did a little research, only to find out that they are rather small (not that I have anything to brag about), unless they come from a very large animal, and then even so, making them not very useful for nuts and saddle material. They are also protected under the same regulations as ivory, and therefore rare, expensive and best to leave them be.

Normally, you have to cook your bone to get rid of all the soft tissue, but as mine arrive semi-cleaned I was able to get cutting right away. I selected the bones in order of thickness, selecting the one with the thickest walls for nuts and the others for saddles, and cut them on my bandsaw using a 1/4" 6TPI PC blade from Timberwolf. I tried to get as many pieces out of each bone as possible and at the same time have them as oversized as possible, leaving a variety of rough cut shapes and sizes to work with. Most of the nuts, however, came out about 1/4" x 3/8" and the saddles about 1/8" x 7/16". The longest piece of the usable leftover were cut into 1/8" squares for tieblock inlays. The rest was either kept for potential inlay material or simply discarded.

It was a little tricky to cut the bone pieces at times. I didn't dare use my hands for these small sizes and irregular shapes and using pushsticks made it a fiddly affair. Most came out in nice straight cuts but some were a little wavy too. Hopefully not more than can be cleaned up once the pieces are worked into their final shape.

One thing I did noticed though was the rather unpleasant, somewhat pungent and heavy smell of what I would imaging a crematorium smells like. I tried not to think about it to much, and stayed focused on not having any of my own bones slipping into the traveling saw blade.

One thing that became clear from all my reading was that it was imperative to degrease the living daylights out the bone before putting them on the instrument. If you don't, or do it insufficiently, the grease will continue to seep out slowly into the wood it contacts, eventually ruining glue joints and what not.

The method one article I found recommended was to first clean the soft tissue of by boiling the bone in hot water for an hour or two, either just water from the tap or in a solution of mild detergent or household armonia. The degrease the bone for 1-3 weeks in Coleman's Fuel while changing the fuel every now and then.

As the bone didn't have any soft tissue on it, I decided to skip the first part and go straight to the degreasing.

I got my Coleman's Fuel from a local sports shop that have a lot of camping gear. I read that it had to be done in a 1-10 volumes but I didn't have a jar that was big enough so I winged it a little and hoped I would be able to compensate with longer degreasing and a few more changes of fuel.

I put all the pieces into the biggest glass jar I had and filled it up to the brim. It immediately started to go cloudy from all the grease released from the surface of the bone. A day later all the residue had settled at the bottom and the fuel had gone clear again.

After 10 days or so I shook it all up again to see that the fuel had gone so cloudy it was almost impossible to see the bone clearly. I changed the fuel, wiped the bone as clean and dry as I could with a rag, put them back in and refilled the jar for a second round. This time there was considerable less grease showing, though still enough to be clearly visible. This cycle was repeated three times.

After thirty days there didn't seem to be anymore grease coming off the bone, or at least the fuel seemed to be as clear as it was when it came from the can. I took the bone out and to my surprise they still felt a little greasy to the touch, but I decided to leave them to dry and inspect them closer.

Once dry they had gone considerably whiter than before. However, I noticed that while some pieces were a quite uniform white, others had darker translucent spots on them. I don't have anything to compare this with but it appeared that despite my efforts they still had residue left in them,
particularly the nuts. What to do? Could it be that I should not have skipped the boiling part after all? Was it simply a matter of the pieces lying to close together in the jar?

Regardless, I decided to start again with the degreasing process, but first all nuts and saddles were prepped by filing and sanding the rough and uneven faces clean, so at least three faces were clean and flat leaving them as big as possible
for final fitting later. The tie block inlays got worked on all four sides to a 2x2mm square stick. The inlay pieces also got sanded to a 1mm thickness.

Let's do it...... in a pot with one gallon of water and 1 tsp of concentrated dish washing liquid. I put the bone in the cold water, brought the water to a boil and turned the heat down and let it simmer for and hour and a half. 1 tsp of detergent was maybe a little too much in this case, since the bone had already gone through some degreasing, but then again maybe not. The 'stew' gave off a lot of foam in the beginning, but at the end there was only little of it left.

When done I took the bone out and dried it with some paper towel. The bone seemed to be a more uniform white than before which I took to be a good thing.

The bone was left to dry for four days and then put in a jar again with some Coleman's fuel for yet another two rounds of degreasing, one week per round. I wasn't able to see any residue in the fuel after either cycles. I looked as clear as if it was straight from the can.

As an experiment, I left a nut and a saddle out of the cooking process and subjected them only to the last two cycles of degreasing in fuel in a separate jar. For what it is worth they continued to be darker and show more discoloration after the final degreasing process than the bone pieces that was cooked in the detergent solution. However, like the case with the cooked bone pieces, there was no visible traces of oils in the fuel afterwards in either degreasing cycles.

I'm a little uneasy about the whole thing. First of all, how do I know for sure that all the grease has gone? Some of the bone pieces still show a little discoloration, but I don't know if that is just the natural color of the bone or if it is oils still left in there. I somehow doubt that letting them sit in fuel for longer will change this, since they have already been in there for much longer than recommended, but what do I know.

Second, as evident in some of the photos below, small pores are showing in a number of the pieces, which I don't believe is a desirable thing if density is something of importance. In most cases the pieces are clean and solid looking, but in others pores are showing here and there which I hope to be able to work around. In a few the pores cover most of the surfaces and I wonder if I would be best off discarding them or using them for something entirely different.

I don't think I am going to use the 1mm flat pieces for inlay. They are very translucent and textures and colors from the wood it is laid into will likely show through the bone. I should either have kept them thicker, or perhaps bone is not really well suited for the purpose in the first place.

A couple of weeks after I wrote this post I decided to go through the degreasing process yet one more time. Despite the fact that the fuel didn't appear to extract any more grease from the bone pieces during that last couple of soaking cycles, it still bothered me that a few of the pieces displayed translucent spots on them. And so I repeated the whole process of boiling in soapy water for 2 hours, drying for three days, three weeks of soaking in fuel in three one week cycles.

If they are not clean by now, I don't know what it takes to get them to be....................

















BONEHENGE ........



After lots of research and speculation I have decided to try and repair a small gap that occurred in the first binding/purfling strip I added. Actually, it's two gaps, each about 0.5 wide, one between the binding and purfling and one around the rosewood veneer line between the purfling and the soundboard.

Had it only been a gap between the binding and purfling, the matter would have been much easier to resolve as I could just have filled the gap with sawdust and glue. But, it's the gap around the rosewood line that bothers me. If I was to fill that I would give a visual appearance of the line growing twice as thick for about 1" and slimming down again to it's normal size. Not good. The question next was how to to fix it.

I had numerous correspondences with fellow forum members as well as a telephone conversation. Several suggestions as how to fix the problem were mentioned. One was to just add some more glue and clamp the binding in. Another was to make some sort of space at the end of the binding, heat it all up to soften the glue, move the binding into place and reclamping it. Yet another, a variation of the second one, but also adding fresh glue before clamping it.

To figure out how Titebond glue would react to heat I ended up calling Franklin International's, the manufacturer of the Titebond glues, tech support to get the inside scoop. A very friendly tech person informed me that all the Titebond glues does indeed do work as hot melt glues and not only once as some had suggested, but repeatedly so. He recommended heating the glue to a temperature around 240-250º F for best results. I asked if it would be necessary to add more glue to which he responded that as long as there was glue in the joint in the first place adding extra glue shouldn't be needed.

I did two little muck ups to run experiments on. One was a 4" long replica of a side with lining and soundboard attached, including binding a purlings with gaps like on the real guitar. The only difference was that I it made from walnut/walnut/spruce rather than bubinga/mahogany/spruce and that it was straight. Otherwise it was dimensioned pretty accurately and it was glued together with the same glue. The other muck up was just some binding I had glued to a piece of bubinga. The idea was to start practicing on the latter just to get a feel for how much heat I need to supply to get the glue soft and then move on to the more elaborate one for a complete trial run.

During the process I tried to reclamp part of the binding just as it was and another part with extra glue added. For some reason I had better luck with getting the binding to stick when I added more glue. I don't know exactly why that was, but I speculated that it may have been because I didn't keep it clamped long enough for the glue to cool down and solidify. Or, maybe I didn't heat it up enough to properly melt and therefore not being able to adhere properly when it got clamped again. Who knows, but because of this I decided that it was probably best to move ahead with the job by trying to open the joint up a little and add more glue.

After some serious procrastination, I took the plunge and got on with it. I opted to drill two small
1/8" holes, one for the purfling and one at the binding centered around 6mm, 1/4", from the side of the neck. This allowed for 1mm for the neck still to have to come off in the final carving process, 1.5mm of slope in the heel from the top to the bottom of the binding, 1.5mm radius of the drill bit and still have at least a 2mm thick wall between the hole and the heel.

I carefully started drilling a shallow hole for the purfling, though it ended up a little deeper from the repeated attempts to get a decent photograph of the process, and a slightly deeper hole for the binding matching it's width. I used my caliper to measure the progress by sticking the depth measuring blade into the hole. I used a hand drill for this which worked really well for this
with it's slow operation; No unpleasant surprises of the bit suddenly digging in and coming through the neck.

Next came the softening of the glue. I was very nervous about this. Not that it would be difficult to heat up the glue for the binding, but because I was afraid of heating up the glue around the linings too, weakening the joint between the soundboard and sides.

With the tip of a household iron I began to heat up the binding, being as careful as possible to keep the iron on the binding only and not overheat the area in general. It's a good idea to empty the iron before doing this to prevent the water from the iron to spill all over. Don't ask me how I know this. With a drill bit inserted into the hole I gently tried to pry the binding away from the neck to create a small gap in the joint where I could squeeze in some more glue. But, that didn't do the trick. Instead of the binding on the body opening up, the little bit of binding left on the other side of the hole gave way.

Instead I resorted to just heating up binding
to soften the glue around the gap and reclamping the bugger in place.

I made as small semi circular cork lined caul out of MDF, that fitted the diameter of the soundhole. I used a flycutter for this. I don't really like using flycutters but the tool worked really well for this application, as the bevelled end of the cutter created a little lip that held the caul in place an prevented it from falling though the soundhole. I did a few dry runs before the real deal, to figure out which clamps to use and where to put them. I found that using three wooden cam clamps covered the troubled area pretty well.

Once that was sorted out, I reheated the binging again as before,
added a little bit of fresh glue on the gap and scraped as much glue as I could down into it with an old credit card and added the first clamp furthest away from the neck. This pushed the binding in place where the clamp was and opened up the gap a little more in front of it. This procedure was repeated for the second clamp, though the gap in front of the clamp did not seem to widen further when it went on.

The third clamp went on about less than 1" away from the neck and managed to close the last bit of the gap. I wasn't able to detect whether the end of the binding had moved further in to it's pocket in the neck or not, but speculated that it must have done just that and it only a very small forward movement was needed to press the binding in place. The three clamps were left in place overnight for the repair to dry.

Once the clamps were off, the binding was scraped flush with the sides and the clue was cleaned up on the top. On close inspection of the repair revealed that the binding was as good as new. I was still able to trace an approximately 0.2mm gap on one side of the rosewood veneer line but it was a lot less than before and not something I think anyone will notice unless you know it's there.

All in all I was quite pleased with the end result, particular in the light that this it was a task I dreaded doing and one that had been hanging over me for a some time.

Onto the fingerboard....