Back in the day they used to force feed the hound dogs a plug of chewing tobacco to de-worm them. It kinda worked at purging the worms because nicotine is a potent insecticide and if you were lucky the dog only puked for a few hours and hated you forever, not so lucky and the dog died. There are better ways....
The point here is: Using a potato is an outdated and irresponsible method. It is only a somewhat effective method of burning the amalgam off gold but it offers up the same same risks of just burning it off in open air. You cannot stand downwind or you will inhale HG fumes and everything in the near vicinity will have HG contamination. You can never use the pan for anything else ever again (Are you confident you can ensure that happens, forever?) because it is also contaminated. And you have a full helping of toxic fried potatoes you have to deal with. What are you going to do with that? garbage can, bury it?.. no way
I would bet that most if not all of the people advocating a potato method have only read about it in a book and it sounded easy so they regurgitate the method to others. but they have never tried it themselves, at all.
DO NOT use any device, container or method that contains any copper or aluminum. If you build a copper retort, corrosion or not, there will be mercury coated to the inside of it after the first use. Some of that mercury will fall out when you shake the deivce but much of the mercury is amalgamated to the copper and can not be rinsed off. The only way to remove it is by the same methods used for the gold. If you store that contraption in the shed for 5, 10, 15 years, it is still just as contaminated as the day you stored it.
Aluminum is readily attacked by HG and you can get a violent reaction. This is why HG cannot be shipped airmail.
Mercury is not plutonium but it must be respected...learn about it before you do anything