A frying pan with old, heavy dirt can be cleaned using one simple and inexpensive product - "Old Paint Remover".
It may vary in brand and price, but you don't need to buy the cheapest one.
It is better to opt for the average price.
Cover the surface with a bag or cling film. The product can be used at home because it does not have an unpleasant odor.
However, the room must be warm.
Pour a small amount of the product into the pan, smooth it out with a brush, paying special attention to the sides and edge. Repeat the same procedure on the back side.
Cover with a bag or film and leave for half an hour or an hour. The duration of exposure will depend on the severity of the contamination.
Very dirty pans should be kept under a bag for 50-60 minutes. This product makes the carbon deposits liquid, like paint.
Therefore, the contamination will be very easy to remove. After cleaning, just wash the pan in the usual way. After such cleaning, they will shine with cleanliness, as if just from the store.