I have made some new fuel tank floats out of cork for a vintage vehicle. They need proofing against 100 low lead octane fuel. Can you please recommend a suitable product? In the old days, they were coated with shellac, but having tried and failed I'm now looking for a suitable resin. Thanks.

Does the fuel contain any ethanol?  If so you would want a ethanol resistant resin or coating to seal over the surface.  You can get similar products from bike restoration places as they have in recent years had to develop better coatings as the increasing amount of ethanol  has been playing havoc with fuel systems on older vehicles, especially with composite tanks and parts in them. 

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

Phenol novolac epoxy is the go.