Strange orange stains on a fresh plaster – what is it and how to get rid of it?

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Two weeks after plastering, in the corner came out this orange stuff with an unpleasant smell. Surprisingly, it's a corner of an interior wall adjacent to an apartment hallway (i.e., no temperature fluctuations). The plaster looks to have dried about a week ago. Only noticed it yesterday. Layer of about 4 cm in this corner. The wall is gypsolite. It has always been dry and there has never been any fungus in the apartment. What happened and what is the most effective way to deal with it?




It may be a "plaster efflorescence" (I forget the exact name). Wipe it off the wall, and if it hasn't happened again in 14 days, it's OK.


This fungus occurs only when the plaster dries, with a lack of ventilation. It occurs in almost all gypsum plasters. Maybe the corner was blocked up or there was no air flow. And since after plastering the walls, humidity increases many times, it is the best thing for the fungus. The 1st thing to do is to ventilate the room. The second is to burn out with a heat gun, so it does not spread. After the entire plaster has dried, knock down to a few centimeters and after priming, re-master this piece.

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