-- non-subscriber, please reply to sender and MMD --

Dear MMD:  Whilst removing leather from bellows constructed in 1910,
I was using a thin penknife.  Eventually the steel became coated with
a layer of copper which must have come from the glue.  Was it the
practice to add a copper salt to hot glue, presumably to inhibit the
growth of mould?  Has anyone else noticed this?

Ted Bowman, UK