I found a really cool Calamites fossil with exquisite detail on a wet day a couple months ago, but after a week or so of keeping it indoors, the details started to fade and the colors became dull. It springs back to life when damp, but that only lasts so long and I fear that annually applying water might eventually wear the fossil. I think I've read somewhere that you can use vegetable oil to keep rocks/fossils looking saturated, but I was wondering if that might cause any structural damage or any other ill effects to a sandstone-based fossil. Thanks!