Tim........nice horn, something I have never fooled with. When you say you colored it with AF, I assume you mean aquafortis? If that is the case, do you handle it the same as if you are staining a maple stock? Do you apply it, dry it, then
apply heat?....Don
Yes it is Aqua Fortis. I clean the horn with rubbing alcohol, coat the horn using a dauber, like you would use for leather dye, let is sit for a while, 30-40 min, wipe it off (I use a paper shop towel) and heat it with a heat gun, I have tried both low and high and except for the time it takes find little difference in the settings. Let it cool and wash it in warm water, dry it and if it is the color you want finish the horn, if not repeat the process. If you get splotches or streaks either you missed that spot or it had oil on it, it can come as simple as your finger tips. If you watch closely as you paint it on you may see little areas that look as if it will not stick to it, like water flowing off a waxed car, that is a sign of oils on the horn of a spot that is scraped smoother that the area around it, as if you missed a spot If either happens you will have to scrape the whole horn down and start over.
Got a little carried away but I hope this answers your question.
Tim