Use of 'straw ropes' and 'fern ashes' in lead smelting - looking through my
e-mails I noticed that this query doesn't seem to have received a conclusive
answer - and this one ins't either.
Straw ropes - these could be another variant on the use of vegetable
material for pot refining of lead. The rope would be wrapped around a pole
or iron bar and immersed in the lead to bring bits of dross to the surface.
I know that the Capper Pass factories at Bristol and Melton used swedes or
mangel wurzels on the end of a pole for cleaning up lead and solder and
grass rope would do the same. The process needs a slow release of moisture
and air which you don't get from wooden poles which char too easily.
However, I have never heard of the use of garss ropes so this is only a
guess.
Fern ashes - another guess. I agree with possible use as a cupel bottom,
perhaps used to improve or extend the bone ash. Small additions would
partially melt and act as a binder for the bone ash. Alternatively, as fern
ashes are mainly potassium/sodium carbonates, they could be added to the
second smelt to make a fluid slag in the slag hearth or reverberatory
furnace. Only a small proportion is needed to significantly reduce the slag
melting point. They might also be effective in removing traces of arsenic,
tin and of antimony from the lead. Caustic soda is usually used (Harris
process) with notrate to dry up the slag.
Regards
Richard
----- Original Message -----
From: "Alasdair Neill" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Saturday, December 03, 2011 9:33 AM
Subject: Lead smelting queries
In looking through a number of Devon lead smelting accounts I have a number
of questions, not having any detailed knowledge of lead smelting.
Firstly, at Wheal Betsy there are various references to straw ropes e.g.
"spinning straw ropes for smelters for smelting". What could these have been
used for?
In addition to the use of bone ash for silver recovery, there are references
to "fern ashes". Would these have been used as a substitute for bone ash, &
is there any record of these being used elsewhere.
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