Issue 40 winter 23 web - Flipbook - Page 72
Once we have received the 99.9% pure lead in ingot form
this is loaded into our smelting pot and the process would
then be:
The lead is then put into the melting pots, which are gas
fired, and melted down. The melting point of lead is 621
degs. F or 327 degs. C, and when the lead has melted any
impurities which are ingrained in the surface of the lead
float to the surface and can be skimmed off as dross. This
dross is reclaimed and again sold separately.
When the pot full of molten lead has been skimmed, it is
then transferred into the pig moulds by hand ladling, the
pigs weighing approximately 88lbs each, and from here
the pigs are transferred through into the Casting Shop,
which is the next step in the process of making cast lead.
Basically, this process consists of throwing molten lead
down a bed of prepared damp sand. This method has
changed little since Roman times and the equipment
needs is very basic. The process consists of a predetermined amount of sand, which is watered and thoroughly
mixed using wooden paddles, it is then roughly spread
across the table, and then using a bar of wood called a
strickle being propelled by two men at each end and
supported by the side beams of the table, the sand is then
roughly leveled off. The strickle is then used to ram the
sand and solidify it, it is then again leveled off with the
strickle. This has brought the surface of the sand down to
its required level and is ready for smoothing to the
required finish, by the use of hand-held copper planes.
While this has been going on, the lead in the melting pots
at the head of the table has been brought up to the
required temperature and is then ladled out into the head
pan. When sufficient lead has been transferred, the head
pan is lifted by means of the pulley wheel and handle and
the molten lead is sent down the surface of the table.
Whilst this is still molten and again using the same
strickle, the lead is planed off to give its required thickness. This is determined by a number of factors, namely
the speed at which the lead is thrown down the table, the
heat of the metal and the speed with which it is planed
off, and also has a lot to do with the experience of the men
involved in the casting. The excess lead is collected in the
tail pan and is then transferred back into the pot at the
head of the table for re-cycling.
Above, Notre Dame Decorative Leadwork to Base of Spire
pressed into the sand on the table before the sheet is
thrown. These are then cut out and formed by hand into
the pipes and head.
As soon as the men with the strickle reach the bottom of
the table, the lead behind them has already set and can
be marked and cut virtually immediately. All the lead used
on our roofing contracts is measured for each specific job
and is cut to size, rolled and weighed individually. Any
lead then left on the table is cut up and again re-cycled.
Sand Cast Lead Conservation Ltd are proud to be a part
of this project as a British company working on a historic
building in Europe and we hope this will lead to many
more in the future both in the U.K and Europe.
In addition to the lead used on roofs, we also manufacture
lead rainwater goods, head and downpipes, and if these
are required with mouldings and patterns, they can be
www.sandcastlead-conservation.co.uk
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Conservation & Heritage Journal
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