If there are any "drying oils" present in the oil (such as linseed, fish or flax-oil), oxidation of the relevant unsaturated fatty acids can be expected to form a polymeric film on the biodiesel/air interface. It reforms every time the surface is broken until it is all reacted with the air. I wonder if that could be an alternative explanation? Michael Allen
have noticed that raw biodiesel from tallow readily forms a skin as it cools, but the same BD after washing does not. Paul Gobert. ....... yes drying oils sound like a possible explanation and Paul's contribution kind of kicks my suggestion out of touch! This could be confirmed by picking up a bit of the skin with a spatula a checking for solubility in water .... Paddy Biofuels at Journey to Forever http://journeytoforever.org/biofuel.html Biofuel at WebConX http://webconx.green-trust.org/2000/biofuel/biofuel.htm List messages are archived at the Info-Archive at NNYTech: http://archive.nnytech.net/ To unsubscribe from this group, send an email to: [EMAIL PROTECTED] Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
