Manufactured in the UK by Conservation Resources, these envelopes are made out of 120gsm sulphur and lignin free unbuffered paper. We use our neutral pH starch adhesives throughout. Envelopes are hand-made with one side and bottom seam only. This product opens along the short side. This quality has passed the PAT test and is ideal for the storage of photographs, negatives or glass plates . Available in packs of 50 or 500 envelopes.