Exposing Photopolymer Laminated Copper Clad Boards With A Peachy

[Pete]

No resin involved at all here. You can get copper board with a film of photosensitive etch resist on. When you develop the board anywhere that has been exposed to UV light dissapears and exposes copper, then you use an etchant to take away copper to leave your circuit under the etch resist.
Over exposing would just mean that too much resist is taken away and hence too much copper will be removed, under exposing means that there is resist left on parts you want to etch away.