I bout a sheet of MDF for 18 bucks at my local lumber yard. Took it home and stored it in my Uncle's barn. A month and a half later I come back and it is sitting outside. I asked me uncle how long it has been sitting out in the rain and he said about a month. I told him that MDF doesn't hold up very well to moisture. (It was raining the past few weeks). He replied "oh bullshit, it won't hurt it any." I go and look at the MDF and it looks exactly how it did when I bought it. No swelling or anything. Is it still safe to use or should I buy a new sheet?