Caul material?

[polkat]

I am going to try William Fulton's plate bending technique as described in the library over on the MIMF site. Since the bending forms (cauls) have to withstand submersion in hot water for a time, what would be the best wood to make them from? Oak maybe? Would it be a good idea to coat them with some kind of waterproof, heat resistant paint? Any ideas? Thanks!

[GMM22]

For maximum stability in hot water I would suggest Lignum Vitae. True Lignum Vitae (i.e., Guaiacum Officinale or Guaiacum Sanctum) might be hard to obtain and costly, but Argentinian Lignum vitae, "Bulnesia arborea or Bulnesia Sarmientoi" would probably do fine. It is fairly common and not expensive.

[upnorth]

I would not coat them with anything and I would use any wood that I had lying around.

Polkat email me at kenmckay@hotmail.com.

[GMM22]

Well, maybe Lignum Vitae is way overspec. Mind you, all of my tooling usually is

[Michael Richwine]

We tried that some years ago. Made cauls out of aluminum, with the idea of saving material. Results were very disappointing, and I think the idea was generally short lived, at least in relation to violins.

If you're going to try it just to test the technique, I'd think you could use anything you want that's easy to carve.

[Andres Sender]

The technique is far from dead. In fact at this very moment I am sitting next to Sam Compton, who bends and is very happy with the results.

Bill Fulton recommended plywood for first experiments, then aluminum for permanent cauls. Sam uses plywood as he is still shifting things around in the technique.

FWIW I'm not an advocate, just an interested bystander.

[Michael Richwine]

Interesting, Andres. We couldn't even get a sound good enough for beginner instruments out of bent plates, no matter what thicknesses and graduation we tried. Is Mr. Compton doing anything radical with thicknesses?

[polkat]

Thanks Andres. I had considered aluminum as well, but I live in a rather rural area where obtaining aluminum plate, as well as machining it, would be a bit of a task. However, we do have a source of marine plywood locally, which I suppose would be more water resistant then regular. We do have a blacksmith nearby (guess this does sound rural, huh?) who might be able to help with aluminum. I'll check.

GMM22, correct me if I'm wrong, but isn't Argentinian Lignum vitae commonly called ironwood, which I believe is quite oily. Would the oily nature be a problem?

Upnorth, I emailed you.

[Andres Sender]

Nonado--Sam says bending allows him to go thinner.

Polkat--you can order aluminum plate by mail from onlinemetals.com, and saw it out on a woodcutting bandsaw or even by hand if you don't mind the exercise. It's messy and unpleasant, but quite do-able. Were I you I'd use any plywood just to get going and worry about improving things later.

[polkat]

Andres, yea, I think I'm going to start with plywood. By the way, has your friend Sam mentioned just how thin he goes with bent plates?

[GMM22]

"GMM22, correct me if I'm wrong, but isn't Argentinian Lignum vitae commonly called ironwood, which I believe is quite oily. Would the oily nature be a problem?"

It seems that every species that is very hard and dense is called ironwood somewhere by some source. I would disregard this convention as it can be confusing. Lignum vitae including the Argentinian has a high oil resin content, and that's what makes it more stable in water than other woods. I do not think it would be problematic. Finished surfaces do not leach. As noted, any wood would suffice for your needs initially. If one was opting for something better long term, I think it would be preferable to aluminum at least in regards to working properties.