Description (From Recipaedia)
A bucket full of paint stripper.Can be used to strip paint from previously painted surfaces and bring them to original appearance.
Crafting
Place a Bucket of water and a saltpeter chunk in the furnace. You get one bucket of paint stripper.
Use
To strip paint from painted blocks, use just like any paint bucket but instead of adding a color, this will remove any previously applied colors. Place the bucket in your hotbar and ONLY select it when you are ready to use it. Then tap the block or item you wish to restore and all the paint will be removed from it.
You can also use the Paint Stripper to remove dye from clothes and carpets. To do so, smelt the item with a paint stripper bucket in the Furnace.