[Jmad]

We recently took a week long trip and I put my cards in our home safe. This is the first time I have done this. They are usually left in a box in the closet. All cards $50+ are in Pro Mold One Touch holders (or one screw if It requires a specific year model). The lesser value cards are in penny sleeves/top loader. There were set in there loose (not in the box I usually keep them in) The top loaders were fine, however, there were a few of the One Touch cards that appeared to be warping/bending. I removed them (10 or so) and sure enough they were arched. I've since placed them in penny sleeves and under a heavy book. They are all fine now. Is this due to moisture?? Does anyone use the Silica packs to combat this??? It was alarming to say the least!