George said:

"Greg G." wrote in message
.. .
From your pictures, you have black mildew, which will grow on concrete, on
gypsum, grout and many other substrates. I'm betting that the
urea-formaldehyde glues used are not particularly appetizing, even if the
formaldehyde has fully outgassed.

My only observation was that, around here, it does 'grow' on MDF much
more readily than say, plywood or solid oak. And that is isn't the
glue it's feeding upon, but the fibers (or if you prefer, cellulose).
And that is doesn't have to be 'wet', only that it has to be exposed
to humidity.

I wasn't talking about paint, or shellac, or varnish or lacquer, but
plain old MDF. Painted or varnished, it's no longer the MDF but the
coating that is exposed to the humidity, so of course it will be more
difficult for mold to 'grow'.

Wrong again. It will grow _anywhere_ because it does not depend on the
substrate for nutrition. Without knowing your particular circumstances, I
would guess that you have placed the stuff near a wall where there is no
circulation to reduce the RH, and plenty of that supplied by a cold wall.
You could have painted the wall or the board with the same result.

Again, I never said it wouldn't grow. I said it grew more readily.
Bare MDF adsorbs moisture and present a more appealing moist surface
for it to grow on. Which probably explains why the formica doesn't
have anything growing on it, but the bare MDF does. And while it may
not depend on cellulose for nutrition, it certainly doesn't hurt.

Sorry you don't want to learn about mold. Why ask the question if you're
not interested in the answer?

Again, I'm not the original poster. Re-read the thread... ;-)



Greg G.