During my experimental stages of processing mylars, I took one sheet and used my heat gun to shrink it down to a ball smaller than a corn kernel. I forget what I weighed it at, but it was almost not readable on a gram scale. But my goal was to take a lb of them and try to slowly heat them to shrink them down considerably, and then put them on high heat, enough to make them brittle and possibly ash up and (or) break apart, leaving the silver in a ball or a pile. I never finished doing it that way.
But I think that if a person do a slow/low heating of the mylars (maybe a day or longer) they should shrink down enough without losing any silver from flying away, it should be condensed enough to apply higher heat to burn off more plastic until most or enough of it's gone to be able to process them further, or to crush them more and to keep the heat going.
If I were to attempt this experiment like I'm describing it, it would be better to do in the winter time, being as though I could justify using that much heat outside.
If I had a fast way to do each sheet or a pile of them at a time using a heat gun, I would because it only took seconds to shrink a mylar down to the size of a small pearl.
Although I don't use any incineration in my processing of the mylars, I wouldn't mind giving a try at a 1 lb batch. I incinerated them in a grill before and I lost silver in the soot going in the air, so open incineration will cause you to lose silver. A closed incinerator with a long tube pipe chimney about 6 ft going up, with a 60 mesh wire screen would allow the smoke and soot to escape and should keep the silver from going up that high.
On another note: Look at the photo below. Are you processing the tabs that have the red markers around them? If not, you're not getting all your silver and your yields will be lower than expected.
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