Posted by js on June 01, 2002 at 20:34:13:
In Reply to: OFF TOPIC- Bass Sax repair posted by Gus Pratt on June 01, 2002 at 15:11:38:
Silver-soldering a crack in a (70-year-old?) instrument and being a novice at it is risky. Silver soldering sheet brass without burning it up is an advanced technique, as silver soldering is best for connecting solid "chucks" together, rather than (corroded) edges of sheet metal.
If you insist in this pursuit, find a very small gauge of brass wire. Cut the brass wire and bend it to lay perfectly in the crack. Apply a good coating of silver solder paste flux to the wire and to the crack, and then lay the wire in place. Heat the wire just until it is red hot, and apply silver solder. Hopefully, the wire will wick the silver solder and allow it to transfer to both sides of the crack - making a strong "ridge" of silver solder right over the crack. Again, this is an advanced technique which requires a lot of familiarity with using a torch like a paint brush. I use this technique for repairing expense vintage cracked (Heckel) bassoon bocals for professionals. (scroll down)
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DO THIS INSTEAD !!!!
Buy some mostly lead-based "crack-filling" solder. Allied Supply and others sell it. They claim it has some silver in it. Maybe it does. This solder tends to "pool up" right where it is applied rather than flow and actually does fill cracks well. The best flux for this type of solder is the "watery" clear acid flux, which often comes with the little "kit".