Thanks for the information on browning. My concern, however, is how do you use, store, and dispose of mercuric chloride safely? It is my understanding that "corrosive sublimate" is a very toxic material.
I store the liquid in a glass bottle and keep a small amount (3-4 oz) in a plastic bottle for use. The amount of liquid that I use on a set of shotgun barrels for example would probably not exceed one or two teaspoons of liquid. In use, I pour say a teaspoon full in a large plastic bottle lid and wet down a cleaning patch size piece of absorbant cloth in that liquid. I keep the cloth in the plastic lid with the liquid and add a small amount of water to the dried out liquid when I wet the barrel down after carding. In between times I have a Windex bottle of water that I just spray on the dry barrel(s) and wipe it around with the above cleaning patch.
A comment was made about dry carding; in my experience, dry carding removes too much of the rust and I alway card with steel wool and lots of water.
Relative to the amount of mercuric chloride actually used; it is a white powder and not very soluable in water. I would have to look up the formula but you dissolve no more than 1 or 2 teaspoons in a liter of water and that will last you for a lot of barrels.
the alcohol I think is in the solution as a wetting agent; ie it reduces puddling on the smooth metal
the reason that I don't immerse the barrel(s) in ferric chloride is that I never had a lot of success with wooden barrel plugs not leaking. Part of that may have been that I immersed the shotgun barrels vertically in a plastic pipe full of ferric chloride solution.
Also keep in mind that the results are highly variable between barrels; on some the pattern just jumps out at you while on others it is quite difficult to bring out the pattern and at best is comes out a pale grey colour.
If the mercuric solution does not rust very effectively I will add a few drops of copper sulphate to it and sometimes that helps.
Finally, the solution is very similar to most of the cold rusting solutions found in Angier's book on bluing/browning. From what I can see all of his several solutions for iron barrels are variations of the same thing and all using mercuric chloride. I kind of suspect that some of the cold rust blue solutions sold commercially today are very similar to Angier and to Gaddy.
One final thought is that the amount of mercury mixed with the rust on the barrels is miniscule.
cheers Doug
