I am not sure that we really know for certain.  There were no patent
specifications at that period, so that the patent only describes the process
in a few words.  It almost certainly involved patterns (probably of wood)
around which the sand mould was formed.  Today this is such a normal part of
casting that no one thinks twice about it.

The difficulty is that we do not really know how pots were cast previously.
I think I have seen something to the effect that guns were cast like pots.
Since there are descriptions of gunfounding, we can presumably deduce how
pots were made.  If so, a core was formed; then a grass rope was wound
around it; and a smooth surface formed over that.  On top of that a loam
mould was created.  The rope was removed leaving a void into which the metal
was poured.  After that the mould had to be broken to get the pot out and a
new mould made from scratch for the next pot.

It is presumed that Darby's process of casting in 'green' sand meant that he
could rapidly (and repeatedly) produce moulds.  The best recent article in
the subject is N. Cox, 'Imagination and innovation of an industrial pioneer:
The first Abraham Darby' Ind. Arch. Rev. 12(2) (1990), 127-144.  She was
able to show that Darby's pots were thinner than those made by the old
method.  With less metal, they were inherently cheaper, quite apart from any
saving in workmanship.  Prior to Darby's arrival at Coalbrookdale many blast
furnaces cast small quantities of pots each year.  Within a few years, this
ceased and Darby appears to have had the market to himself, that is until
there began to be imitators after his patent expired.

I see your source is Samuel Smiles - I do not regard him as a source to be
used, except where he is quoting documents which are not available to us
today.

Peter King

-----Original Message-----
From: Arch-Metals Group [mailto:[log in to unmask]]On Behalf Of No
Name
Sent: 25 April 2005 18:58
To: Peter King
Subject: Sand casting developed by Abraham Darby

I posted this to the Britarch list and was
advised to post here instead.

I read that Abraham Darby developed a system
of sand casting that allowed for mass production
of iron bowls.
Also that the sand casting basics were obtained from
Holland, and he imported Dutch experts, who along with
his brass casting experts from Bristol, developed this
process for him.
http://www.worldwideschool.org/library/books/hst/biography/IndustrialBiogra
phy/chap6.html
I am aware of basic sand casting, but could someone
give me a description on Darby's process?


Thanks,
Edgar