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Black vitreous substance


I’m currently studying medieval pin manufacturing. Type A wire
headed pins are described by Chris Caple as having “two twists of
wire stuck onto the top of the shaft with a flux or adhesive”. The
flux or glue is described as a “black vitreous substance”. Further,
“Analyses and observations under the Scanning Electron Microscope
have shown that usually two phases are present in the black vitreous
matrix. (i) a seemingly hard or dense material which contains
copper, phosphorus and calcium. (ii) a seemingly less compact, more
porous matrix, the major constituent of which is tin, possibly in
oxide form. The black glossy appearance of this substance suggests
some form of flux or glue, rather than solder or corrosion product,
which, as it alone secures the head wire to the shaft, attests to its
deliberate use. The present lack of coherence in analytical or
structural for this material prevents any definite
character being given to this substance.” Does anyone have any
suggestions as to the identity of this mysterious substance? mark
shier – Gaukler Medieval Wares


Mark, your “black vitreous substance” sounds like what I get on my
copperwork when I use Phos/Copperbrazing rods. This is a self fluxing
material for copper. Your mentioning the copper, phosphorus, and
calcium analysis is what made me think of this. Hope this is a clue.