<html> <body> <blockquote type=cite class=cite cite=""> Is polythene impervious to acetone?  Where might I find a sheet of it? </blockquote> Hi Dave,                    You can get polythene in sheets at any hardware store, and yes it's impervious. Dale, has given you a similar spin. leave the steam alone, just keep flushing <G> Don't be shocked if you use a pint to a quart of acetone.  And yes, you need lots of ventilation, a face mask will also make life more comfortable. I either do the job in the shop, or on the customers door step.  Don't even think of doing it in the home. A hair drier can help to gas off the acetone a little quicker. If it is key top hardener,  it will take a few weeks before you really get a full idea of where the tone will end up. If you over do it a little, (but I doubt it) wait at least a week before doing any further chemical treatment. Minor reshaping with 320 grit paper will bring the tone back up in brightness a little. A little ironing with a warm voicing iron will stabilize the felt. Regards roger </body> </html>