The acidity present in bad quality mats and other framing materials can cause serious damages to the artwork. This alteration is commonly known as mat burn. In this case, this print by the Spanish artist Picasso was completely disfigured by the stains that the mat caused. Even if not always is necessary to wash the artwork to remove the discoloration caused by the mat, in this case, other than the mat burn, there was a severe overall discoloration. It was necessary to wash the print to remove all the acidity and degradation products that were in the paper. The results speak by themselves.