On Jan 5, 15:45, quapla(a)xs4all.nl wrote: it NOT plastic. Acetone, MEK, toluene, and many other organic solvents are sometimes supplied in 1-litre pastic containers but should not be kept in plastic for long-term storage. Even polythene bottles will be damaged in the long term -- they go brittle as the plasticisers are leached out. Such things are normally kept in glass bottles for small quantities, say up to 500ml, or metal tins for a litre or more. Is it kept somewhere warm? It should be kept cool (no more than 68deg F). If it's reasonably pure acetone, I can't think of any reaction it should have with steel or tin, so I guess what you're noticing is evaporation causing a slight pressure buildup in the can. Unless it's contaminated -- it doesn't co-exist well with some other solvents (such as chloroform) and moderately strong oxidising agents, or some catalysts (including some forms of carbon). If it's rusting, then you should probably replace the can before it becomes weak enough to leak. -- Pete Peter Turnbull Network Manager University of York