Today I noticed that my MDF cutoff box was covered inside and out with a white and green powdery growth. I'm not smart enough to determine what it is.

None of the other wood in it had any growth on it - except a piece of MDF.

I checked the rest of the wood in the shop and it all looks fine.

Granted, the conditions are great for this to happen - un-airconditioned garage in south Texas in the middle of the summer following weeks of rain. Temperature in the high 90s and it feels almost as humid.

I'm new to MDF. Is this be expected? 20 years in this shop with never a problem on regular wood, particle and pegboard, plywood, or high density particle board.. There's even lumber here from the last owner that looks like it just came from the lumberyard.

The majority wipes off easily. Plans are for a light wipe-down with bleach and then to poly it.

Comments anyone?

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.. .
Today I noticed that my MDF cutoff box was covered inside and out with a
white and green powdery growth. I'm not smart enough to determine what it
is.

None of the other wood in it had any growth on it - except a piece of MDF.

I checked the rest of the wood in the shop and it all looks fine.

Granted, the conditions are great for this to happen - un-airconditioned
garage in south Texas in the middle of the summer following weeks of rain.
Temperature in the high 90s and it feels almost as humid.

I'm new to MDF. Is this be expected? 20 years in this shop with never a
problem on regular wood, particle and pegboard, plywood, or high density
particle board.. There's even lumber here from the last owner that looks
like it just came from the lumberyard.

The majority wipes off easily. Plans are for a light wipe-down with
bleach and then to poly it.

Comments anyone?



Look for a leak. Takes 16-18% MC, so they say, to support mildew. At least
it wasn't the ugly black stuff, just the more benign "hairy" white.

The majority wipes off easily. Plans are for a light wipe-down with bleach and then to poly it.

Comments anyone?

Sounds good to me - bleach should take care of it, but anything water-
based won't be very good for your MDF. The bleach will kill the
fungi, but the MDF will absorb the water in the bleach. If this is
just your scrap box, I'd seriously recommend taking the whole box out
of your shop and tossing it in a dumpster, while breathing as little
of the dust/spores as possible. I work with a variety of fungi/molds
at work right now, and some can be pretty unhealthy. Your MDF mold
might not be too dangerous, but many fungal spores are allergens or
irritants even if they're not pathogenic, so I'd err on the side of
caution. I might even spray it with bleach and then throw it away.
If you really need to keep these particular cutoffs, you could try
bleach or alcohol, but setting them out in direct sunlight for a whole
day should do the trick too, then a good coat of poly/shellac/etc.
Any chance you could get a dehumidifier or better ventilation in your
gar-shop for the rest of the summer?
Good luck and stay safe,
Andy