Forgive me if this is a silly question. I've just started a project at removing every bit of paint in my house to be redone. I've run into, what i think is green paint? on the bottom layer of each wooden item (doors, skirting boards etc.) The heat gun does not react to whatever substance that is. I'm hesitant to sand it just yet in case its lead based paint. Just sanded the top corner to see how difficult it was to remove. The answer is very. I've been doing it outdoors so not too concerned but interested to know what substance it is. The house was built in late 1800s. Whether these are the original doors, i couldn't say. The lock mechanisms are pretty ancient.