I heat treat bamboo to make flyrods. I use what is called a heat gun oven. Basically two sizes of stovepipe with insulation between. I get the temp up to 320* and leave the strips in for 15 minutes. I have also used the propane torch method but on the whole clumnot strips or lams. Yes it turns black, steam comes out, even catch fire. But we remove the rind anyway. I file the nodes down before “flaming”. Can’t see why it wouldn’t work on lams, just have to be careful not to let them catch fire. The black stuff will come off with steel wool.
Ovens like mine are homemade and except for the heatgun (1200 watts) cheap to make. Try searching “heatgun ovens”.