I dug a bottle full of a tar like substance and it wont dissolve in lighter fluid, paint thinner or peroxide, hot water softens it, but I don't want to boil the bottle for fear of breaking it... any suggestions?
I know for sure this worked for a friend. Buy paint remover in gel form. Put the gel in the bottle filling haft of bottle that is tar free and then allow it to stand for two weeks. After two weeks take a wooden dowel rod and stir the gel and weakened tar together then pour out all content the will come out and fill with new clean gel. Repeat process ever two week till tar is completely gone. In my friend case it took eight week to get the whole bottle tar free. Hope this will help you. Let us know how it goes.
That resembles the Dranoâ„¢ technique I used last summer on a gunked-up Hostetters.. I also used a wooden dowel to excite the action and pull semi-dissolved gunk out.. took about a month, but it did work..