Stan;
The posting I made on this was taken directly from an Ithaca service manual. They only mentioned using the cold blue. From other sources Tincture of Benzoin is the chemical to use by the same process to add yellows, just alternate with it & the cold blue. When I first tried this back in the 80's I obtained the Tincture of Benzoin from mry local drug store, don't know if is something still available or not. I tried it both ways at the time & personally preferred the colors without the yellows, just as described by Ithaca, so never used the Benzoin again.
The beauty of this finish is at the temps involved absolutely no danger or damage is involved to the gun. "If" you get a coloration that suits then all is well, "If Not" simply polish it off & proceed to bluing, you would have had to polish it anyway, as 8-bore suggested. You would have lost only a little time & a few drops of cold blue in the interim, so is no great expenditure involved. You may happen to like the result.
I believe the Perazzi frame was made from an alloy steel unsuitable to the traditional bone charcoal process so that was not an option.
