On Jan 4, 10:06, Philip Pemberton wrote: RTC, I MEK is indeed methyl ethyl ketone, aka butanone. It's not particularly toxic, nor particularly dangerous -- very roughly on a par with iso-propyl alcohol, and less dangerous than some solvents that have been mentioned on this list for use on plastics. It's used industrially to "weld" ABS and PVC, as a cleaner in the printing industry, as a degreasing agent, to clean equipment used for plastic foam (including cans of the expanding urethane foam filler used in the building industry), and as a constituent of some plastic glues. It will dissolve most ink and some paints. Like IPA, acetone (nail varnish remover), methylated sprit, etc, it's fairly flammable. It will attack a lot of plastics, but not most epoxies (once properly cured) or "waxy" plastics like polythene. The effect on potting compund will depend on the compound, but it will make some types of RTV (Room Temperature Vulcanising compound) "silicone" swell and eventually make some types crumbly. BTW, the acetic acid given off by curing RTV is rated as 10-50 times more toxic than MEK :-) -- Pete Peter Turnbull Network Manager University of York