

Using the cheapest 'acid-free' paper you can find and thinking that you are covered for decades is going to cause you heartburn at some point. The paper can also still contain a substantial amounts of Lignin.

This is the fallacy of acid-free paper marketing how much buffering a paper may contain to neutralize the acidic Lignin organics is undefined. If you have Lignin in the paper, you have the potential to produce acid over time. Lignin is the 'stuff' (organic substance) that binds cells and fibers in wood. You can also find a large amount of paper marketed as 'acid free' even when it includes recycled wood fiber! Any time you have wood fiber in the paper it means that there is pulp and the resulting Lignin. If there is high humidity and temperature conditions, or if there are large variations and swings in the temperature and humidity, the need to consume the remaining neutralizing buffer reserves is much greater. And the ability to neutralize is impacted by the environmental conditions. It might be able to neutralize the paper for 10 years, it might be able to neutralize the paper for 1 year. As time and environmental conditions evolve, the buffer that is held in reserve can be drawn upon to neutralize the paper. Paper, like water, has the ability to hold buffer in reserve. Throw a bit in there, and you can sell it as 'acid free' paper. How much they add, how 'acid free' the paper really is can be anyone's guess.

There is no industry standard for 'acid free' paper manufacturers use the term 'acid free' simply because they do not add any acids during the production process and/or add some Calcium Carbonate for buffering.
