Paper mache is going mouldy, is there anything I can do to stop it now?

Dry it as fast as possible. Or start over, using thinner layers of papier mache and allowing it to really dry between coats.

"Sealing" the papier mache with anything is just going to keep the water in the object and allow the mold to continue to grow. Most of the mold is actually within the papier machine -- you're only seeing the fruiting bodies on top.

You should be able to kill it by preventing air from getting to it (by drying as much as possible, then completely coating with something waterproof like clear polyuethane, colored acrylic or latex paint, or a permanent white glue (diluted 3 or 4 to 1 with water...same as ModPodge), at least.

You can also "kill" it and remove the blackness (if it's mildew) by applying a solution of bleach and water for a little while (speed up in the sunshine if you want). Then you could also seal it to prevent further problems, etc.

Next time you do papier mache, be sure and let one or two layers dry thoroughly in a warm/breezy/dry place before adding the next layer or you'll have similar problems.

HTH,

Diane B.

Yes, you use polyeurathane spray that you purchase at Home Depot or Walmart. Not that cheap, but that is what you use. A small can would be cheaper, if you want to paint it on there, but most people spray it. But you can paint it if you want to.

It does not cost a fortune. $5 <= can of poly <= $10

Save and reuse what you don't use up. Spray on old newspaper.