So maybe I could stain the horn with an iron solution (vinegar & iron?) and deter the little buggers? Or soak the horn in it!!!
Since I don't do scrim work on horns I really don't mind a color change. Just want to stop th bugs 
...............................Lynn
With an iron dye I have done it both ways.
I have soaked horns in a nitrate of iron bath and have simply wiped it onto the surface of the horn after it was shaped and smoothed. You must insure that there is no oil from your hands on the horn or the dye cannot wet out and sink into the horn. A good rub with rubbing alcohol will remove any skin oil.
If the horn has a lot of white color the dye will not take on the white portions. Areas of the horn with little or no pigment will dye well. The sections with no pigmentation are more porous than sections with pigmentation.
You might also experiment with copper dying for the green color.
Historically the green dye would have been a strong solution of copper acetate. But copper acetate is toxic and tough to come by. I have made it myself using sections of copper pipe in a crock with wine vinegar. As it was done in days of old.
But an easier way is to simply pick up copper sulfate at a garden center. Make a solution with as much copper sulfate as you can get dissolved in the water. Then simply de-oil the horn and soak it. When you remove it from the dye bath have a wood plug handy to stick in the open end where the plug will go. The horn is fairly pliable out of the dye bath but it will shrink as it looses water during drying. So you want to keep the hole circular until you install a plug after the horn drys a few days.
I never had any luck working with the copper dye where I simply swabbed it onto the horn as I did with the iron dye. I could only dye them green using a bath.
At one time they had used the copper dye to protect animal hides on their way to a tannery. Used in areas of the world where common salt was simply too expensive and the climate did not permit sun drying the hides before shipment.
