boiling is not a good way to soften horn for changing its shape permanently
look on horngild.org
Hope this is legal, but here is an extract of one old article:
Whether by the grill, which takes a practiced eye, or by the oven, which takes a 300 degree setting, or by the fryer, at no more that 320 degrees of wet heating, the goal is to make a piece of horn plastic so that when it cools it will not loose its strength, but will loose the memory of its old shape and permanently retain the memory of the new shape. The only time a horn should be boiled is when the bone core is separated from the horn after the horn is removed from the cow (we strongly recommend doing this 1.) after the cow is dead, and 2.) outside!). And, so, a deep, dark mystery of the horn trade is answered by the indubitable Horn Swogglers