MITRA Forum Question Details

Sorry for the belated reply, Kristin and I were away to celebrate our daughter’s 2nd birthday.

I am not an expert on these paints but it is my understanding that Flashe paints are bound in a poly vinyl acetate dispersion. Like acrylic dispersions, they are not resoluble once dry. I would think that adding a small bit of water should work fine. The various emulsifiers, dispersion agents, etc. should help to keep mold growth down. There is already water in the paint formulation so I do not see how it would contribute mold growth unless the water you add has some mold spores. Using distilled water would avoid even this possibility.

Dipping brushes directly into paint jars can introduce spores, so it's always a good idea to dispense paint with a clean metal or plastic instrument (e.g. spoon). I like the suggestion of using distilled water. Antimicrobials in water-borne colors and mediums can lose potency in long-term storage, and it's not uncommon to see some mold growth in old, previously opened containers. Ivory Black seems particularly vulnerable, maybe because the pigment is a good growth medium, or because mold prefers a dark environment. One of our paint chemists recommended Lysol spray (that specific brand, original formula) to retard mold in acrylic containers- a light spray on the product surface before sealing the jar. He said the active ingredient was also commonly used as an anti-fungal in acrylic house paints​, and that the alcohol carrier would not affect the overall condition of the paint.

Really interesting Matthew. I have experience substantial mold growth on aqueous pigment pastes of ivory black and yellow ochre even when some ethanol has been added. I have not seen any on tubed or jarred commercial acrylic dispersions nor in Elmers glue (which is a dispersion of PVA).