Sealing a stage

All right guys... I am building a stage for fire performing, and I was wondering if any one had any input on thompson's water seal vs polyurethane to seal it. I wasn't sure if either might be better.

Well I know polyurethane is flammable before it dries and I would have to assume that if you had a fuel spill or enough prolonged exposure to an open flame then it may be possible for it to catch fire.

I would say though that if the possibility is significantly small on the poly catching fire then it may be a viable option. I would suggest putting sand in the mixture to add traction as fuel will no doubt splash on the stage and the poly surface would become quite slick. You may even think about weather treating the wood and then doing a poly coat on top of that to provide just that little bit extra protection since you will probably want to be using the stage long term.