Should you be worried?
This is something that is starting to become a concern in the canning community, some canners are experiencing brown or black spots under their lids after sealing them tight. Here's what steps you should take to make sure no harm was done to your food. First, simply scratch the black spot with a utensil and check for any hairs. Next you want to check how it smells to see if the lid or the contents in the jar are giving out any strong odors. If there's no presence of hairs or odors then that's a good sign. Finally you want to note if the seal was still strong and check for resistance when opening the lid. If the seal was good then the black or brown spots on the lids should be harmless. This is because the undersides of our Denali lids have an enamel coating protecting them. If this coating on our lids gets a tiny scratch or imperfection it can cause a chemical reaction with the natural compounds in food. Usually, this is associated with the proteins in the food, mixed with the heat from pressure canning or water bathing. In return this causes these compounds to be released that create these harmless black or brown spots under the lids. These spots are not harmful; they are just unattractive.