Hi all,
When drying freshly cut sugar maple and Manitoba maple i often get a black fungus or mold that penetrates the wood. Throughout the whole slab in Manitoba. We mix hardwoods so we do dry fairly slowly. We go slightly slower than wood species 3 in the woodmizer HD manual. Is there anything i can put in the kiln or coat the slabs in that would prevent this? We mill to 2 1/4 - 2 1/2.
Any advice would be welcome.
It is likely that it is mold fungus. Avoiding the mold requires fast drying to eliminate the surface moisture. Note that this could be a different fungus, but the cure is the same.
is there anything i can put on the slabs to prevent its growth?
I'm shooting in the dark a little here because I don't know all of your process, but with the maple at least, the issue is too slow drying when there is too much moisture in the maple, leading to fungus and deep discoloration of the wood itself. I believe you have two different things going on, first mold on the surface, and then enzymatic discoloration of the deep wood itself. Surface mold is easily prevented and requires fast drying and high airflow. Enzymatic stain is very problematic in maple, and requires cool temperatures and fast drying. Schedule 3 is a low and slow schedule and would be guaranteed to discolor fresh sawn, high moisture content maple.
So although you can apply anti fungals to the surface of the wood (Timbore, Boracare, etc) it won't do anything about the enzymatic stain deep in the wood. Two different process caused by much the same reasons, too slow a drying rate, too high an initial kiln temperature and not enough airflow.
What moisture level are you starting at in the wood? What species are you mixing?
You mention you are doing mixed loads of fresh hardwood and maple, but the two are generally incompatible in the initial stages of drying, and only become compatible when you can hit a pretty high wet bulb/dry bulb depression at all times, without overdrying any species in the mixed load. Schedule 3 has very small WB/DB depressions until the final stages, and would guarantee too slow of drying of maple and resulting issues as you describe, but would be good for some other species, which I assume you are using it.
Without knowing your situation, the easiest answer is to not mix the loads until everything is well down into the 20% or lower range, and this can be done easily by placing large fans in the maple in a drying area for several weeks to flash off some moisture. Surprisingly, this will actually remove moisture faster than in the kiln because you are forcing it to slow down in the kiln, and getting mold. Fan drying will prevent this and speed the process up. It also evaporativly cools the wood so also prevents mold and enzymatic stain.
At lower moisture levels, the mixed load maple will not mold up.
What YH says.
Some woods need to dry slow to prevent checking and similar defects.
Others need to dry FAST to prevent staining.
Some are more forgiving as they have natural resistance to staining, but dry easy (cedar etc)
And some are just a problem :D
Once the wood gets to ~20%, fungus wont grow, and it's pretty hard to stuff up in the kiln. So air drying the maple with fans, then finishing in the kiln might be an option.
I would recommend air drying down to about 30% then finishing in the kiln.
Manitoba maple is a soft maple commonly called Boxelder in the US.