When PVA is exposed to humidity, water molecules slowly creep into the polymer structure. Because the water molecules are really attracted to the polymer chains, this happens faster with PVA than with our other materials. The water molecules actually push the polymer chains apart, decreasing the effective glass temperature of the material. When too much water is absorbed, the material becomes moldable at room temperature and the filament will melt together. Wet PVA prints with a lot of bubbles,