A letter dated October 2, 1730 John Wightwick to John England, of Principio:
The Potomack piggs [Accoceek] will not reach 5£. 15s. they being cheap piggs are
fittest for founderys... We have sold some of these last arrived, but the
dealers complain they are too white, if they were grey they would go off much
better... for we have pretty near an equal quantity of grey piggs mixed with the
white which inclines me to think this must be some mismanagement of the Founder
that they are not grey. I therefore hope you will consider and give directions
to the Founder accordingly, and let the Hearths at both works be always set
Burrow and not Transheer, for white piggs will do us great prejudice in the
sales... there will be a difference of 10s p. ton in the sale betwixt grey &
white...
I have found another reference to burrow and transheer, but in relation to the
arrangement of the plates in a finery forge. Schubert (1957 p 279) talks about
the plates in a finery hearth being adjustable. These could be angled to yield
more iron or iron of better quality. Angling the tuyere plate outwards
("transhaw or transiring from the blast" Dud Dudley 1665 p31) or away from the
blast (Rinman vol 1 p 566). The iron was "lesse fined, more to the Masters
profit'. This moved the melting pig away from the nose of the tuyere and it was
less oxidized. Slanting it in or making a "Burrow work" put the tuyere and pig
closer together and decarburized it more.
So how does this apply to the operation of a blast furnace? Might it have to do
with the angle the tuyere is aimed? Somehow "burrow" raises the temperature,
causes more silicon to be reduced, which encourages the formation of gray pig.
But, by implication transheer must increase the yield of the furnace?
Thanks
JH Brothers IV
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