Lead?
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In Maryland, there is an historic city called St. Mary’s, which has had and continues to have quite a bit of excavation and study. The restored parts are open to the public.
Anyway, several years ago, there were coffins discovered that had lead linings. I can’t remember anymore what the archaeologists’ thoughts were as to the reason for the use of lead. I am thinking that it would be to delay the onslaught of the soil organisms, but I am just guessing.
You are correct. Lead and lead oxides kill bacteria, fungus, mold mildew and algae, though they were unknown organisms at the time. Lead also would absorb all the oxygen in the coffin fairly quickly in the form of lead oxides......