Cast Two Collet Brooch
The model for my replica is a UK metal-detector find
with no provenance. It is a Deavy Class 6b brooch? , with multiple
collets and no bosses. Made of a copper alloy, it is 2.5cm in diameter
and 7.5mm tall. It has two tall collets for now-missing stones, and the
collets contain white paste. The ring has been decorated with blind
drilling and file-work. The pin is missing.
I decided to cuttle cast my replica, as it is a medieval technique that I have some familiarity with.
Cennino d'Andrea Cennini (c. 1370 – c. 1440) describes "di
seppia, di quella che gli orefici adoperano per improntare", "cuttle
such as the goldsmiths use for casting (impressing)".
Medieval cuttlebone mould in the Museum of London
I took a pet-store purchased cuttle bone, and sawed
the end off, using a hacksaw. I then cut it in half (badly,
but that didn't affect the process).
I took the antique brooch and pressed it into one
side of the cuttle. Next, I cut pouring gates in both pieces, and
air vents in the impressed half. I bound both halves together with
masking tape, and pushed it into a sand-filled replica medieval pot. I
then melted some bronze (using modern equipment), and poured
it into the inlet.
I tossed the cuttle into a bucket of water, and
waited a moment for it to cool. Opening it revealed a successful cast.
I cut the sprue off, and finished and polished using
modern tools. I drilled out the collets to match the original, as the
casting process filled in the holes.
I chose to set green glass cabachons in the brooch.
In the regulations of the Goldsmiths of London, it was forbidden to set
real gemstones in anything but silver or gold: "'ne dreit piere ne fust
assis en latout n'en quivere..."? Most of the surviving glass
stones in my annular brooch collection are a particular green, which I
was able to match closely. I cemented the cabachons into their
collets with a mixture of Plaster of Paris and casein glue, as this
seems to produce a good match to the cement often seen in surviving
brooches, and is similar to both traditional jewellery practice and
I finished the brooch by fitting a sharpened brass wire pin.