Hi! I have a long Calph grill thing that is 1/2 ribbed and 1/2 griddle. It is long enough to cover two stove burners. I have an electric stove. I think the grill/griddle is from their non-stick line (not anodized or stainless steel). I want to grill meat, and I know I have to preheat it, but how long can I safely let it pre-heat on high heat? I had a lovely huge Calph fry pan that warped, I think from too high heat (I never did figure out how it warped). I'm afraid of warping or otherwise ruining this thing. Any idea how long I can safely let it pre-heat on "high"?