wrote in message
I built a work table in my basement (really a kind of desk) out of MDF.
It turned out really nice. I used a helmsman indoor/outdoor spar
urethane to seal the MDF.

Is there anything I can apply to 'post cure' this flawed urethane?
Without having to do a bunch of sanding?

Spar varnish was probably not the best for the job, but now you have to work
around that. I'd try some heat. Not a lot, but a lamp that would raise the
surface temperature a bit for a couple of hours. Another method is to
contact MinWax and as for help.

http://www.minwax.com/listserv/askminwax.cfm