Guardhouse glassines are made of a PH neutral, semitransparent paper with no harmful chemicals. Safe for stamps and coins, they are also commonly used to protect photos, negatives, invitations, artwork, gift packets, seeds, crafts and more because of their water, air and grease resistant properties. Guardhouse glassines are carefully constructed with flaps folded on the exterior of the envelope, leaving only a smooth interior pocket surface that will not catch on stamps or other contents. Our glassine envelopes contain un-gummed flaps and are ideal for all of your philatelic materials. Guardhouse Glassines are made with 55 gsm (38#) paper.