This is a general question for the group, especially chemists: It seems that the issue of copper absorption into silicone (and then leaching back out) comes up all the time in this forum. (Most commonly when people are buying pre-owned aquariums, and worried about previous use of copper medication). It also seems like nobody is entirely sure whether the silicone takes up the copper or not, so we've decided as a group to stay on the safe side and not risk putting an octopus in an aquarium that has ever been exposed to copper. So here's the question: Couldn't we do a test and resolve this once and for all? I'm not a chemist, but I do work at a university and could probably cook up an experiment if given some guidance. For example, put a few blobs of silicone on some glass samples, soak them in a variety of common copper aquarium medications, clean them off, then test for copper residue. We could do acrylic too, while we're at it. The first part is pretty straightforward, but I have no idea how to test for the copper residue. In the end, what we care most about is the re-cuprifying (made-up term) of the water. What if I soaked the samples in aquarium-type saltwater for a while and measured the water for trace amounts of copper? I think it would only be convincing if I used an extremely sensitive copper test, and perhaps soaked for a long time. Any ideas? Suggestions? Finding that there is copper would give an easy answer, but finding no copper would be tougher: What kind of test would convince you that there was really no copper left (to the point that you would trust putting an octopus in such a tank)? For example, what level of precision would the residue test have to be (reading zero) to be low enough?