Why are cooking sprays so bad for nonstick pans? Speaking to the  New York Times’ Wirecutter ,  Fran Groesbeck , a managing director of the Cookware and Bakeware Alliance trade association, said that – ironically – some non-stick sprays can ruin the coating on your pans.  They can leave a thin film behind after use, she said, and it’s especially hard to spot on nonstick pans. “You can’t necessarily see that residue, because nonstick coatings are all black, but if you don’t properly clean it off after you’re done cooking, then your food will start to stick.”  This film is  made up of ingredients  not usually seen in non-spray oils, like soy lecithin. As they linger on an often-reheated pan,  they polymerise , becoming next-to-impossible to remove. But that’s not the only unwanted side effect.…