Mafuta ofunikira a Birch ali ndi fungo lakuthwa modabwitsa, lamphamvu. Fungo lake lodziwika bwino limalimbikitsa mpweya watsopano, wopatsa mphamvu. Akagwiritsidwa ntchito pamutu, amapanga kuzizira kwapadera.
Ubwino
Methyl salicylate nthawi zambiri amagwiritsidwa ntchito pamutu kuti apereke mpumulo wapanthawi ndi apo ku minofu yocheperako kapena kusalumikizana bwino. Birch amaonedwa kuti ndi mafuta ofunikira kwambiri, chifukwa chake kusungunula ndi mafuta onyamula kumalimbikitsidwa kuti agwiritsidwe ntchito pamutu. Kuziziritsa, kutonthoza kwa Birch kumapangitsa kuti ikhale yogwira mtima popaka minofu kapena kupaka minofu ndi mfundo. Ndi fungo lake lamphamvu, mafuta ofunikira a Birch amathanso kuwongolera fungo ndikutsitsimutsa mpweya.