Here's the gear you'll need:
http://www.baroqueflute.com/tour3.html
Rod Cameron has experience with the process:
http://launch.groups.yahoo.com/group/ea ... ssage/2890
"Having made many experiments, I feel that boxwood original flutes were acid stained first and then mounted in the lathe between cones to be turned down at the sockets for ring fitting. Real ivory will be discolored to yellow by nitric acid. Imitation ivory is unaffected.
For those who have wondered about the best way to normalize any residual acidity after nitric acid staining a boxwood flute, I recommend not to bother soaking or wiping with alkalis such as baking soda or ammonia. Just a little bit of overdoing this will spoil the deep lustre that acid staining gives to the wood's appearance, and instead a rather dull look results. Having tried many different approaches, nothing works as well for me as soaking the stained flute in RAW linseed oil, heated to about 45 degrees C for at least 24 hours. If the flute has already been turned down thin at the sockets to receive rings, then there is a danger of the thinned wood warping during the warm-oil soak. Adding the rings to a stained flute is not a problem and avoids warpage.
For reference, my acid staining procedure is to mix conc. nitric acid into warm water at about 50/50 ration, stir well...some heat will be generated. While still warm, and OUTDOORS, or in a fume cupboard, add iron in the form of small brad nails ( perhaps one or two 1" nails per half a cup of acid/water). Immediately the nail will bubble and dark brown, poisonous fumes will be given off as the nail decomposes. These fumes are very damaging to health, so do not take any chance that may lead to inhaling them. When you are sure the resulting mixture is free from fumes, the flute may be stained using a Q-Tip cotton swob as a brush. The flute may be oil soaked after it appears to be dry. Air temperature affects the ability of the acid to 'bite', so don't stain in a cold place.
Trained chemists will be able to describe exactly what's happening, but my understanding is that the water allows more oxygen, the iron is a mordent and necessary to avoid the unsightly 'black speckles' that appear overnight on boxwood that has been stained only with conc. acid. The iron will not dissolve into the water/acid mix unless either the iron or the mix are hot. If a nail is dropped into the mix and sinks to the bottom with no reaction, then fashion a tweezer of boxwood to hold a second nail, heat the nail and immerse half way into the acid. Once the nail is boiling nicely push it down to the bottom of your glass container until it touches the first nail. Immediately, like an electric contact, the first nail will start to boil and dissolve. More iron makes weaker acid but a darker stain. Th warm raw linseed oil soak ( I am pretty sure it was Cathy Folkers who suggested to me years ago the warm/raw tip...thank you, Cathy!) serves to normalize any residual acidity that lingers in the wood. A sure sign that this has not happened properly is the dark fingerprints around tone holes once the flute has been played for some time. The oil soak does the job without spoiling the lustre. You may set up a good oil soak tank by using a plastic insulated food cooler such as used for car camping. Buy a tropical fish tank heater with thermostat included, and a small immersible plastic water pump (for fish tanks) to keep the oil stirring. Use some inner pastic box with lots of holes to hold your flute parts so that none of the joints touch the immersed heater. If that happens, as darker spot will result where the temperature of the wood got a little too hot."
UK one)