->The two mills at Pontesbury had reverberatory furnaces by 1860 (3 + a slag
>hearth at the Stiperstones mill and 4 + a Castillian furnace (for slags) at
>the Snailbeach mill)..
>
>Also at that time, some of the lead was being converted into red lead - so
>it is just possible that the 'drass' furnaces were some sort of oxidising
>device.
>
>See Percy:
"The process of manufacturing red lead comprises two distinct stages, the
first in which lead is converted into protoxide, and the second in which the
protoxide is converted into red lead, the sole agent of oxidation in both
being the atmospheric oxygen aided by suitable heat. In the first stage
the temperature should be considerably below the melting point of protoxide
of lead, and in the second it should be considerably lower than in the
first. The first stage is in some localities termed "drossing", and the
product "dross". The second stage is in some localities termed
"colouring", and the product "colour".....
(Percy's Metallurgy 1870 Vol 3 part 2 page 509. ) Descriptions of drossing
ovens, colouring ovens and the processes then follow.
Cheers
Ian Forbes, Killhope
|