I don't think so. I have used Oscar's solution (more or less) quite a few times and it usually works well. Having said that, I should also add that about 10 % of barrels, the pattern jumps out at you no matter what you do, 10% the pattern will not come out for love nor money and the rest are somewhere in the middle. If the pattern is not coming out, I add a small amount of copper sulphate to the solution and sometimes that helps. It often copper plates the metal but the plating will rust away after a few hours. If in full panic about the copper, wipe it with lime sulfur tree spray which turns the copper to a sulphide and it cards aways easily (at least for me)
Prompted by a friend who also uses the solution I also tried using a much more dilute solution on barrels with tight twisted patterns and it does seem to help. Such barrels are much more difficult to develop the pattern on that the simple spiral straight lined type.
A good etching with ferric chloride between rustings seems also necessary to bring out the pattern as per Oscar's writings.
cheers Doug
