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I recently purchased a "new" wood violin bow on eBay with a broken tip. I easily repaired the cracked wood using super glue and a short segment of 4.5 mm diameter carbon fiber rod bored perpendicular to the crack.
Once assembled, I noticed that the stick has a slight twist and the hair is not properly aligned. I went to Youtube and noticed that bow makers set the camber of the stick by heating it with an alcohol flame. I think that I can do this to remove the twist, and since I only paid $12 for the bow I can be pretty brave in the attempt. However, I don't want to do a lot of varnish refinishing (assuming success) if I can avoid it. I saw a Youtube video where the varnish was covered with a anti-oxident coating before the flame was used on it, but naturally the material was a trade secret and I don't know what the material was. I hate videos like that.
My first thought is to use a silicone grease since it is stable to about 800 F and the wood becomes limber at about 330 F. I also have a anti-sputter paste that is used on mig welders to protect the electrode that may also work. I have no idea on how to remove these materials from the stick, but Simple Green is my guess. Any suggestions, particularly those having previous successful experience, would be appreciated.
I got some more information. I received a PM from someone that took a bow making and restoration class which "used a brown block of something that looked like buffing compound to run on the stick to protect the varnish during bending and cambering." She gave me the instructor's name and I sent an email today. I will report back if I hear anything.
I figured that it was time to do some experimentation with fire.
I purchased a dual wick alcohol burner from Amazon (wicks are covered with copper tube which produces a lot more heat than the conventional wick alcohol lamps I have used in the past).
The test wood violin bow was an inexpensive one I got from eBay because it had a broken tip. Varnish of unknown variety. I coiled the hair at tip end to keep it from the flame.
The first material I tried was Dow Corning #4 Electrical Insulation Compound. This is a non drying silicone grease that is NSF approved (you can use it on food processing equipment). I applied a light coating on the bow shaft with my fingers and subjected the shaft to about 3 minutes of flame, keeping the shaft in the flame (above the flame is hotter) and kept moving and rotating the shaft. I noticed a slight amount of bubbling of the coating in spots. Removed coating with paper towel. No damage to varnish was noted.
The second material I tried was NAPA Sil-Glyde #76-1351. It has a stated working temperature range of -20 F to 600 F. Same procedure as above. No bubbling of coating was noted. No damage to varnish was noted but the grease took longer to remove. This material is heavier than the Dow Corning #4 and forms a thicker layer.
The third material I tried was Forney MIG Gun and Contact Tip Nozzle Gel #37031. Same procedure as above. After about 30 second within alcohol flame, the coating started to smoke. The varnish was obvious tacky and stuck to paper towel.
I think that the original material I saw was a high molecular weight paraffin wax used to lessen friction on band saw blades. I have a tube of that coming to test.
The NAPA Sil-Glyde looks promising, but I would not try it on an expensive bow unless you practiced a lot on cheap ones first.
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