Eli5: how does formaldehyde work in preservation?

Question

Always hear it being used to preserve things, but why?

In: Chemistry

Answer 1

organic matter decomposes when in contact with moisture and bacteria. check out that peruvian mummy that was found recently, ancient but very well preserved. the reason is more or less the same as formaldehyde – when there is no moisture, and no bacteria to decompose = the tissue remains intact.

for the peruviana, it was altitude and frigid cold that preserved the body. but formaldehyde can provide a barrier that no moisture or bacteria can enter, regardless of the surrounding environment.