I've used WWG terrain for years. I do not recommend sealing it with anything.
In fact, as a trial, I took two Mayhem Street tiles, sealed one with a spray and left the other alone. Then after drying completely (several days as I was too busy to get back to it), I did two tests.
I spilled cola on both (as if I were playing a game and knoicked over the soda) and ten quickly dabbed up the liquid with paper towels.
And I put them both in the sink and poured a gallon of water on them.
The untreated tile (after it dried out) was slightly stained, but flat and still very usable. The tile that was sealed warped as it dried (since both sides of the foamcore panel and street cardstock sheet could not breathe).
Nothing I did could make it lay flat again, and I had to toss it. I tried pressing it with heavy books, ironing it, even bending it. And I ended up with a creased yet totally warped tile (with a slight iron imprint … just kidding).
So I've never sealed them with anything. They wear well, any occasional spill can be quickly taken care of (paper towels at the ready, plus that careless gamer can be easily buried out back in the National Forest).
It saves money NOT sealing them, and mine have not warped in several years of usage, and several years in storage (in the Pacific Northwest where it rains 385 days a year, and in the SOuth, where humidity reaches 110%).
I suspect that sealed tiles may actually slowly warp over time just absorbing the moisture int he air, and then not being able to dry out on all sides evenly.
YMMV of course.
journeys to and from the Australian national convention - and tells us what he thinks of panicking tank hordes and flat terrain!
