At the Salt Cellar we've decided that each tile we sell for cooking needs to be broken-in, or 'cured', by us. We do this for for a number of reasons. First, the procedure involves a couple of hours to do it right. We need to heat the tiles gradually up to a temperature of 500 degrees and then let it cool down. This this takes several hours and it makes sense of us to do a whole batch of them at once. Second, sometimes even good-looking blocks are really flawed and they break apart during burn-in. Last, it is possible that a block contains a small amount of water. If this is the case the block may literally explode (as one did in my oven last week!). Interesting. So as a safety issue we'll take some of the 'excitement' out of the process for you.
Once the block has been successfully cured it can be heated to operating temperature much more quickly. Still, it is a good idea to start on a low temperature to get the tile warmed up. Then you can turn up the throttle. Wait until the block is fully heated before tossing on the fish or meat.