Q: What is Acid Burn and how to prevent it.

A: Acid burn appears as a shiny coppery color on the surface of photographic paper. It will generally be located along the edges of the print close to the edge of the matte. It can also occur highlighted in the dark areas throughout the print. Occasionally it will appear as large patchy areas of discoloration, usually yellowish brown to coppery color scattered throughout the print.

It most often occurs when non-acid free matte board is used in framing. It can also occur when prints are stored in a sealed area like a plastic bag with cardboard as a support. Cardboard is not acid free. The acids in the matte board or cardboard will begin to leech out over a period of time. When they are trapped under glass or in a plastic bag these gases have nowhere to go. The gases then begin to react with the photograph causing what is known as acid burn. Depending on how high the acid levels are, will determine how long before acid burn occurs. We've seen acid burn happen as quickly as 6 months and as long as 5 years, the average being about 2 years.

To avoid having to reprint pictures down the road, we have a few recommendations. Air is your best prevention for acid burn. Allowing air to freely circulate around the print will prevent any chance of acid burn. This is not always practical, because some prints will be framed under glass. So under those circumstances, always use acid free matte board when framing photographs. This means for the front and back of the photograph. Don't scrimp and use cardboard for a backer. Many framers will use cardboard on the back and then seal the back of the frame with paper and framers tape for a finished look. This will seal the acids that will eventually leech from the cardboard into the frame. Because there is glass on the other side, which does not allow gases to escape, eventually acid burn will occur. Make sure all materials used in framing are acid free.

If you  store prints in plastic sleeves, again make sure the plastic is acid free. Never store prints with cardboard sealed in plastic for any length of time. Cardboard is very unstable, it is made of the same type of materials as a newspaper. Everyone knows how quickly a newspaper turns yellow, well cardboard is doing the same thing, you just can't see it because it's already brown.