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Arching and rib height adjustment


Alex_E

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I seem to recall reading a post at some time that mentioned that very high arched instruments should have the rib heights reduced considerably and that very low arched instruments required higher rib heights.

If this is so, is there a desired internal air volume cubic capacity, as that reference point would allow the correct rib heights to be calculated for any given arching heights?

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Hummm, I think it's better working with a model such as a good Strad or Del Gesù than measuring the internal air volume.

The Hills say that sometimes Strad had to use wood that just permitted him to make a flat model, but that was compensated by deeper ribs.

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Ahh, I'm glad you included that 61-64mm range rather than just the 64mm you've mentioned before. I've been thinking about this a lot the last several days because I started working on my second violin again and almost have the outside of the back done, and I was worried I couldn't hit 64mm with the heights I had planned. Given my rib height in the center of the instrument will be in the 31-31.5mm range (due to it being 32mm at lower block and tapering evenly towards the upper) I would have to have averaged greater than 16mm for both the back and front and I didn't really want to go that high. I was thinking 15.5 or 16mm for the back and 15.5 for the front. Sound reasonable to you?

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Yes, I read a book of my local library by a luthier (Mr. West? in West coast ? ) in 1900. In the book there was a picutre of him and his 200 violins. He claimed (speaking of authority)the volumne of air (in box) to area of the opening of the f-holes should have a certain desirable ratio. Too big a f-hole will lack power;too small will result nasal sound. It makes sense to me.(shape is not all that important?). Try to blow an empty bottle across the top (without a cap). Air collides at the top. Too Big a mouth would not make sound. Well, I just want to report it to you. Something worths your discussion.

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Hi Seth

Any particular reason for the even taper of the ribs, as opposed to the usual top bout only?


Yes, because Chris Johnson and Roy Courtnall said to. On page 76 to be precise.

No reason other than that, really. Keep in mind their book was my primary teacher, and you all on Maestronet and some articles on MIMF supplemented the book. I've gotten a lot more from the net these days than the book, but that's how I started it.

I'm thinking of doing the upper bout only like Michael does it on #3.

Also, a constant taper starting at the bottom block and tapering evenly to the upper block is really easy to do.

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I don't have the book - that's interesting. How's it going with #2?


Well I was working feverishly on it and made some mistakes in the purfling groove on the back and just backed off and didn't get back to it for a couple months. I've been working on it again. I'm nearly done the outside arching on the back. When this is done I'm gonna hollow it out and glue it on the ribs, which are done. Other than the little gaps between purfling and groove in place because of my retardation in going back over the groove with the dremel to "clean up" the groove, I'm really liking how it looks. My repair to the button has turned out well with the exception that I miscalculated and didn't splice it in deep enough so that the end of the splice butts up against the purfling rather than being underneath it. If you look close, and know what you were looking at, you could tell it was spliced. 99.99% of people who see this will never know.

I took some black and white photos of the repair, and of the back in general, and am waiting to get them back from development. I'll scan some in if they turned out nicely and post them. The back's further along now than the latest of the photos I took.

With this back I decided to try out the Roger Hargrave method of using a gouge to cut out the channel area over the purflign out to the edge, and then round over the edge from there. I made the gouge I'm using, and I believe that it's not curved enough and my channel will be about .5mm deep. I don't think that's such a bad thing. I'd have preferred if my homemade gouge had a bit more of a curve to it, however.

So as I carve the edge down, carefully, approaching 3.5mm channel depth, which is what I'm going by (not the edge height, which at this point is around 6mm), I'm lowering the whole back. It's all roughed out, however the back at its highest is now around 16.7mm. I want to get the channel all the way around down to 3.5mm and get the middle of the back down to 16mm, and then blend the whole curvature back in starting from the channel and working back up towards the middle.

One interesting thing. Of the 5 sideways and 1 longtitudinal arch template that I created using Elder Thomas' program, I only have 4 of the made. They are the upper bout and corner, lower bout and corner. I haven't got the C bout template made, nor the longtitudinal. And you know what? I don't think I'm gonna. I'm gonna eyeball it. I'm really looking hard at this arching as it's taking shape and getting close to where it'll be done. I'm looking at it from all directions, from the side, with light throwing shadows, etc. And I feel like without holding as slavishly to templates I'm really forced to see the arching itself, and learn it. I'm feeling rather invigorated by my decision not to make the other arches, and just use my judgement.

I've made some aluminum madder rosinate according to Michelmann's recipe, and dissolved some in turp and mixed it in with some mastic varnish, adding a few drops of asphalt. I think it's about where I want it, but I'm gonna have to heat up the varnish a bit in my glue pot to get all the madder resin redissolved. It seems to be saturated in the solution right now and has left some madder resin on the bottom of the jar. I know this will dissolve back in if I warm it up.

I've ordered 4 ounces of propolis for $15 and I plan on making propolis soap with it according to Bill Fulton's recipe. What's funny is that making propolis soap, madder lake, and aluminum madder rosinate is almost exactly the same process. In the case of the propolis soap it's dissolve some propolis in water with lye, add alum, wash, filter and put the wet condensate into a jar. With madder rosinate it was dissolve rosin into water with lye, add madder tincture, add alum water, wash with water, dry the condensate. With madder lake it was stew the madder roots in potash water, filter, add alum water, wash with water, dry the condensate. See a trend? It's all pretty easy once you've done it.

I'm really anxious to see what this propolis soap looks like. The maple I got from Ciresa is pretty porous, and I'm hoping the propolis soap does a good job filling and sealing it. I'll just use clear mastic varnish on the propolis after it dries, then varnish like normal.

By the way Jacob you know what my maple looks like. I looked at yours carefully at the Tarisio auction and the maple you used looks exactly like my one-piece back from Ciresa. All the way down to the pores in the wood and the dark annual ring lines. It's the same wood.

Anyhow, that's what I'm up to. I figure I'll probably get the outside of my back done this weekend, maybe even get started hollowing it out if I can tear myself from the computer long enough. Hopefully I'll glue the back onto the ribs before next weekend and really start having something that looks like a violin. I still haven't done the top or the neck. I failed to get a perfect joint twice on the top and sawed the plates apart and haven't tried again. I'm gonna clamp differently this time and I assume I'll get it right. There ya have it.

As I've mentioned, my digital camera's out of commission right now and we returned my wife's digital camera and got a film camera instead. So there'll be some lagtime whenever I wanna put pics up, however I have a slide/film scanner now so I can still do it. I'll try to get some kinda progress on my #2 up soonish.

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It sounds like you're having fun.

Initially I didn't use arching templates. Then I started using some of the Strad poster ones and nearly went crazy till I found out that the height of the belly longitudinal arch won't match the height of some of the cross arches because of distortion. These days I sort of combine eye-balling and templates, but all these are dependent on my understanding of the arching principles of a given model. As you may well imagine, this understanding is at best less than perfect.

At one time I used the propolis soap. It dries to a powder mostly, so don't have too high hopes of its potential as a filler. Eventually I stopped using it, because I couldn't figure out a reason for using it either tonally or aesthetically.

I'm not advocating this, but twice when the belly joints were not good enough I just let the glue dry properly and then gave the inside a good whack on the joint with a hammer. The glue duely gave.

Oh, for a digital camera - perhaps one day I'll be able to afford one.

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It sounds like you're having fun.


Yeah. I've been doing a lot of things lately, mostly on my computer, but I do find it very relaxing to sit down and carve and scrap on my violin. I even clamped the back to my computer desk and carved on it while playing a slow-action computer game for a couple hours. I took a picture of that, when I get it back I'll scan it in.

Quote:

At one time I used the propolis soap. It dries to a powder mostly, so don't have too high hopes of its potential as a filler. Eventually I stopped using it, because I couldn't figure out a reason for using it either tonally or aesthetically.


I'll be interested to see how this turns out. As long as this powder fills the pores of the wood and then soaks up the varnish I lay over it I'm sure it won't be going anywhere. That's all I can expect of a filler I suppose. Can you comment on the color of this after it's been clarified with the application of some clear varnish or rosin oil?

Quote:

I'm not advocating this, but twice when the belly joints were not good enough I just let the glue dry properly and then gave the inside a good whack on the joint with a hammer. The glue duely gave.


Hehe. I think I'll pass. No offense, mind you.

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"I'll be interested to see how this turns out. As long as this powder fills the pores of the wood and then soaks up the varnish I lay over it I'm sure it won't be going anywhere. That's all I can expect of a filler I suppose. Can you comment on the color of this after it's been clarified with the application of some clear varnish or rosin oil?"

Thats' the thing - it doesn't seem to fill up anything after the application of varnish. It can leave darker streaks in places if it is not absolutely even and smooth before applying ground/sealer/varnish, and by the time one has worked it down to this kind of smoothness there isn't much left. No influence on colour whatsoever after application of clear sealer/ground/varnish.

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Hmm, well this is not the same description of it Fulton gives, and another violinmaker whose site I found who uses propolis soap.

http://www.cranfordpub.com/otis/on_varnish.htm

Note this guy also mentions fuming with ammonia as a possibility. I'm not going to do that.

I've already ordered the propolis. I'll make the soap and try it out and I'll let you know how my experience goes. I suppose like everything else this is a "your mileage may vary" sorta thing.

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Interesting. I'm not sure that his recipe actually makes a soap. The whole plan he gives on his page is a good one, and well organized, though--that's a good resource.

If he left it at propolis and lye, he'd have propolis resin dissolved in an alkaline solution. That may or may not technically be a soap, depending on how it's done, I suspect. This is a common way to make water-soluble resin solutions: the base of drafting ink, for instance, is a resin in borax. You can do the same thing with many resins--shellac is one common one that will work this way.

However, when he adds the alum, he's precipitating the base of a lake pigment, probably mingled with propolis. It's unclear exactly what's going on here, chemically, and if what's left can really be called a soap--it's perhaps sort of a propolis pigment, in a way.

Not that this is a bad thing--I just wonder precisely what's going on, that's all. Violin makers have a way of redefining chemistry in a way that wouldn't necessarily make sense to chemists. :-)

I once made a ground coat from the whole of bee stuff cooked with lye, and what I got may have been more technically a soap than the above, I think wax was an important component in that. As a ground, it worked quite well. It smelled awful, which is interesting, since the raw material smells great.

Propolis is a Sacconi thing, and one of those modern "romantic notions"--I think any actual evidence for it in classical instruments is extremely scant and questionable--all that's been seen is a pollen grain here and there that might more likely come out of the air onto a drying varnish layer than from propolis, as has been suggested.

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It can leave darker streaks in places if it is not absolutely even and smooth


I played around with this some in the past and had this streaking problem--especially on the top with raised grain.Propolis is different wherever you get it and some can be extremely intense.

For a while what I would do is sand between varnish coats using this "soap" or even an undried madder pigment or combined--let it dry and then lightly sand it to even it out before varnishing over it--kind of a dry glazing technique and at the same time eleminating the grinding process of the pigment. This had some interesting posibilites but required too many "glazes" between coats and didn't produce enough color for me.By the way--this worked with spirit varnish as well which some say a pigment cannot be ground into a spirit varnish.

I also found the undried madder pigment had some nice results rubbed straight onto the bare wood and didn't have the streaking problems the propolis did.

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Interesting. I'm not sure that his recipe actually makes a soap. The whole plan he gives on his page is a good one, and well organized, though--that's a good resource.

If he left it at propolis and lye, he'd have propolis resin dissolved in an alkaline solution. That may or may not technically be a soap, depending on how it's done, I suspect. This is a common way to make water-soluble resin solutions: the base of drafting ink, for instance, is a resin in borax. You can do the same thing with many resins--shellac is one common one that will work this way.

However, when he adds the alum, he's precipitating the base of a lake pigment, probably mingled with propolis. It's unclear exactly what's going on here, chemically, and if what's left can really be called a soap--it's perhaps sort of a propolis pigment, in a way.


You'll notice my comment about the similarity between this and the aluminum madder rosinate as well as madder lake. This propolis "soap" recipe is exactly the same as making aluminum madder rosinate, except you use propolis rather than rosin, and don't add any madder coloring.

Makes me wonder if one could in fact make an "aluminum madder propolisate" by following this propolis soap recipe and adding tincture of madder to the propolis/lye solution before adding the alum. The attraction of the madder rosinate is that it dissolves in turp. I wonder what properties the same thing made with propolis instead would have?

This is sounding more and more like Sacconi after all. I recall he did in fact have propolis based varnish recipes in this book. I'll have to break it out again and see exactly what he said to do. I realize you're dubious about Sacconi's varnish chapter Michael, I'm just curious whether or not we're reinventing Sacconi's wheel.

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Just to cloud the mixture further, propolis, or bee glue, is not any one specific substance. I've seen it in a lot of colors, from pale yellow-green to dark red-brown. Bees do not produce it like wax, they gather it, typically from tree buds or evergreen bark. In a pinch they will use any gummy substance they can find. (caulking? roofing tar?) According to Dadant's "The Hive and the Honey Bee" it dissolves in "acetone, benzene, and a 2% solution of sodium hydroxide. ... Ethyl alcohol ... somewhat less effective ... is not as hazardous."

Dadant goes on to say of this chemically complicated substance, "a representative composition... would be,say, 30% waxes, 55% resins and balsams, 10% ethereal oils, and 5% pollen." I believe that exactly what it is will depend on the year, the season, and the nearby mix of tree species.

Many human uses of propolis have to do with its antimicrobial or fungicidal properties. One old beekeeper told me that chewing a piece of propolis will cure a sore throat. It tastes a bit like turpentine.

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And you know what? I don't think I'm gonna. I'm gonna eyeball it. I'm really looking hard at this arching as it's taking shape and getting close to where it'll be done. I'm looking at it from all directions, from the side, with light throwing shadows, etc. And I feel like without holding as slavishly to templates I'm really forced to see the arching itself, and learn it. I'm feeling rather invigorated by my decision not to make the other arches, and just use my judgement.


Well done Seth... I used the templates to learn the shape, but by the time it came to actually carving it, I found the templates were causing me to be over cautious, so I put them in a drawer and just started hacking! The end result is quite beautiful... whether it sounds any good or not I'll just have to wait and see.

I got a lot of information by closing my eyes and feeling the flanks with my fingers. 'Figura della donna'

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