Propylene Glycol is listed on Ebay UK (http://cgi.ebay.co.uk/1-L-PG-MPG-Propylene-Glycol-1-2-Propanediol-9...|66%3A2|65%3A12|39%3A1|240%3A1318|301%3A1|293%3A1|294%3A50). As the original Edward Craven Walker patents give Propylene Glycol as a suitable additive to the water content of a lamp, I'm wondering whether anyone has tried using this substance previously in Lava Lamp refilling?. It has a specific gravity of 1.036, so it should be possible to use roughly the 70% water/30% Propylene Glycol mix that the patent mentions, obviously the proportions would need "fettling" for the best (or any!) flow. I must admit I'm tempted to get some and have a go, having several cloudy/empty Mathmos lamps around the house.