Sometime ago I recall hearing that some types of matte medium contained talc and should not be used as a fixative for ballast and/ground cover as the white talc will bleed through. Well I tried to renovate an old coal mine scene showing the mine as abandoned with the piles of mine tailings around. I opted to use pink foam that I sculpted to look like large piles or small hills of mine tailings. I first painted pink foam with a black latex paint then coated with matte medium and used WS ash as a final cover. The area was done some time ago and is completely dry. I noticed rather quickly that one area on the side of the tailings pile that has what looks like a water mark edged in white. It actually looks like someone spilled something on it which I know is not the case. I'm really quite pleaed how the scene came out with the exception of that white stain. Anyway I checked the matte medium container's list of ingredients and did not see talc listed as an ingredient. Any ideas what it could be?
Yep it's the matte medium. It'll dry with bleed lines around the outer edges. They look like little cracks of concentric white lines. All you have to do is make up a jar of diluted MM in water and then let it settle out and pour off the glue from the top. Pretty simple really. My old layout had tons of it. Was very frustrating. BTW I used artist matte medium, I think it was liquitex. I do not recall it listing the talc either.
That is what I used too [liquitex]. The funny thing is this only occurred in one area about 1" x 2" a rather small area when compared to the total area I did with that same bottle. No problems with it elsewhere.
