I still have more than a quart of Bristol Part A, and two dried up bottles of the hardener. I asked their tech guy about using another urethane hardener...of course he didn't think it would work, but did mention that it contains a portion of the "super glue" chemical...which is why it dries in the bottle if not handled with kid gloves. A very annoying drawback...along with the tiny bubbles that I've sometimes encountered. That said, it's tough stuff. I'm going to experiment with some automotive urethane hardener and a tube of super glue this Spring. Bristol's $25 plus shipping quote for a bottle of Part B struck me as extortion anyway.