Re: Wood stains

[Chris Burt <chrisbur@microsoft.com>]

| Also used on boxwood and other light woods, usually by fuming, which is to
| put the item to be stained in an airtight box with a container of nitric
| acid and add some iron (old nails usually) to the acid and close the lid
| (quickly).  The nitric acid plus iron produces NO2, that orangish cloud you
| see in polluted sunsets, which surrounds the wood and reacts with it,
| coloring it permanently.  The advantage to fuming is that it is much more
| controllable and even than wiping the nitric acid directly on the wood with
| a rag (and easier on the hands!!!).

Time for another lurker to emerge. I was trained as a vioin maker, over 
20 years ago, and have built violins (baroque and classical), violas, 
cellos, viols da gamba, and viols d'amore. I'm now a technical writer 
at Microsoft, but am currently setting up a workshop for building 
violins, violas, and cellos.

I've some practical experience with the incorrect use of nitric acid on
boxwood that helps illustrate an advantage of the fuming process:
	I once wiped nitric acid onto 14 boxwood viola d'amore pegs. In a
few months, the gentleman who purchased the instrument from me complained
as the bulbs of the pegs were twisting off of the shafts. The acid
significantly weakened the wood fibers. This experience happened 20 years
ago, so I've forgotten the exact concentration of nitric acid that I used. 

Two questions:
	What concentration of nitric acid is recommended for the fuming process?
	When did the fuming process come into general use for violin fittings?

One caviat concerning storage of nitirc acid:
	I kept the bottle of nitric acid tightly capped and stored it in a 
wooden cabinet. Iron and steel tools kept within several feet of the 
storage cabinet rusted and continued to rust until I got rid of the 
acid.