I had a bunch of blocks to press and not thinking, kept pressing them on the same spot on the ironing surface. My ironing surface is a hinged top over my cutting surface and mat. When i raised the 'lid', I noticed my mat had a nice big bubble. I just put the 'lid' back down for a few hours and the bubble was gone-mat good as new. BTW, My ironing surface is 3/4" wood and this happened with no steam.