I tried borates on some old rotten trunks and it was clear after two years this treatment leaches out and kills the tree outright-kaboom. Don't use borates. I have been leaning on acrylic wood hardener for ease. Epoxy can be a pain to use. Acrylic wood hardener (wood petrifier and others) can be warmed (and the rot area too) to aid in penetration. Creativily drying punky areas (lights, bagged dessicants, hair driers) really helps the effectiveness of penerating wood stablizers--reapplications usually are required too. I recently heard Shaner thins Acrylic wood hardener by 50 % with water but I have not. Lenz uses acrylic wood hardener now too but then he uses penetrating epoxy and Minnwax solvent based wood hardener in certain situations last I knew.
On tough rot resistant woods(larch cedar juniper) I dont' usually use epoxy or hardeners and just use tinted lime sulfur especially at ground levels-- it helps for me and is safe.
On tough rot resistant woods(larch cedar juniper) I dont' usually use epoxy or hardeners and just use tinted lime sulfur especially at ground levels-- it helps for me and is safe.