Definition: Refers to paper and other items that do not contain acids. Acids can cause paper to discolor, become inflexible, and eventually turn brittle over time. Acid can also destroy photographs or various other elements if it comes in contact with them. If preserving your projects for years to come is important to you, you should avoid the use of paper and other items that are not labeled "acid free".

To be considered Acid Free, an object must have a pH level of 7 or above.