Cyanotype is an antique photographic process, the original blue print. The prints are archival, however yellowing may occur if prints are exposed to phosphates or high pH solutions. Please take care when laundering your garment--I recommend turning your garment inside out and hand washing with cold water when necessary, followed by line drying in a dark room. Use care while handling cyanotype prints, as sweat and hand oils may also cause discoloration. If you feel soap is needed, be sure to use non-phosphate soap. Too much washing and the print can fade. To brighten the blue, try washing in a diluted bath of hydrogen peroxide.