Poster paint is a common type of tempera paint that is gum-based, opaque and usually brightly coloured. While poster paint is great for art projects and kids’ crafts, it’s not so great when you accidentally get some of it on your clothes. You should attempt to treat the stain as soon as possible—the longer you wait, the harder it will be to remove. Make sure to treat the stain before washing the affected garment.
Apply some full-strength liquid washing powder to the stained area and rinse the fabric. If this doesn't completely remove the stain, go on to Step 2.
Mix some all-fabric powdered bleach with water to create a diluted solution. Pour this solution into a container and soak the garment in it. If this doesn’t remove the stain, move on to Step 3 to try another method.
Create a solution of liquid chlorine bleach and water. You can use this to soak the garment if it is white or light-coloured, but bleaching can change the colour of the fabric. You may want to test the bleach solution on a hidden area of the garment. Soak the garment in the diluted solution for 15 minutes. Proceed to Step 4 if bleaching is not possible or didn’t remove the stain.
Apply a colour-removing product. Make sure to follow the directions on the label of the product to treat the stain. This will take the poster paint out, but it will also remove all of the colour from your garment. This step is not recommended for coloured fabrics. After applying the product, wash and dry your garment.