Thanks for the input. The naphtha didn't touch it. I called Steve, the former owner/builder. He said that he had noticed the stuff, couldn't remove it and decided it was a problem for another day. I think the problem is for today so I cut the tank apart. It looks like some sort of slosh/sealer. I noticed where the naphtha was sitting for a few hours it scrapped off easier. I will take it to my EAA meeting Wed and get some opinions (note that the spelling of "fuel" in the subject line has been modified).
Thanks again, Pete Gauthier
