Auteur Topic: How to make a brooch  (gelezen 2113 keer)

aureum

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How to make a brooch
« Gepost op: november 01, 2007, 00:44:42 am »
How to make a  brooch



Metal
Though iron, silver and even gold were also used, most Roman brooches were made from copper alloys. The common alloys were bronze (copper + tin), leaded bronze (copper + tin + lead) and brass (copper + zinc), though up to a quarter of brooches were made of other copper alloys containing different amounts of tin, zinc and/or lead, such as gunmetal (copper + zinc + tin). Each alloy has a distinct colour so the alloy used would have been obvious to all. Brass was effectively a Roman introduction, though it was first imported into Britain just before the conquest. Its golden colour made it more valuable than copper or bronze, and it was initially used mainly for ritual objects and brooches, as well as military fittings and coins. Analyses have shown that each brooch type or design was made from a single alloy or a limited range. This holds good wherever the brooch is found. For example, Aucissa brooches from France and Britain and identical brooches from Israel are all pure brasses. Ore mixes had a variety of effects. Lead, for example, made a cheaper alloy but one unsuitable for sprung pins.


Rare Celtic Brooch Mould, dated 2nd / 1st cent. B.C.

Dimensions :- 7 cm x 3 cm.


Shape
Brooches were made either by hammering a piece of metal into the right shape or by casting molten metal in a mould. The moulds most archaeologists are familiar with are made of fired clay. Those for Romano-British brooches are normally two-piece moulds formed round a pattern. By taking the mould apart, the pattern could be removed and re-used to make another mould – the beginning of mass production! The re-assembled moulds were used once, broken to remove the casting and thrown away. It is surprising therefore to find so few. A reason for this may be provided by two recent finds from Norfolk of metal two-piece moulds. These could have produced hundreds of brooches in a very short time. Most were probably melted down and made into new moulds once the originals went out of fashion.

The wheel brooch was made in a stone mould like this one. You can see that it is part of a larger mould used by the jeweller to make several brooches at once. Molten metal was poured into the mould and then left to cool (this is called casting). When the metal hardened, powdered enamel was put into the channels left by the casting process and fired (cooked) in an oven or kiln.



Roman mould, made of bronze, 4-5th century AD. The mould seems to have been used to make high-end brooches in gold or silver, as it does not cast a catchplate or pin attachment. To its right is a silver brooch made from a wax produced by this mould.   4.5cm., approximately one ounce of silver.


Decorate
A third of all Roman brooches found in Britain have some applied decoration, and most of the rest have relief decoration that is cast in, chased, punched or engraved. About half the applied decoration is champlevé enamel and a further third tinning, a thin coating of a tin-rich alloy covering some or all of the brooch’s surface (often erroneously described as silvering). Sometimes tinning was combined with other metal inlays to produce a real polychrome effect. The enamel on British-made brooches is usually of the type described as simple – one colour in each field – but occasionally juxtaposed enamel blocks of contrasting colour were used, in the fashion seen on brooches made on the continent. More complex enamelling, such as spots inserted into an enamel field, or millefiori (in which slices were cut from bundles of different coloured rods fused together) are normally only found on continental brooches. Other types of decoration include beaded silver wires or repoussé-decorated brass sheets soldered to the surface of brooches, and glass ‘gems’.

Brooch mould from Dunadd



naar aanleiding van deze mooie thread Serie-productie Fibula's ...met dank aan Menno

zie ook: Metalworking Moulds from Old Scatness Broch

zie ook: Small Scale Bronze Casting in the Early Middle Ages



mvg leon
« Laatst bewerkt op: november 01, 2007, 03:06:27 am door aureum »

Offline Menno

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Re: How to make a roman brooch
« Reactie #1 Gepost op: november 01, 2007, 01:01:47 am »
Mooi verhaal en nuttige aanvulling, Aureum.
Op deze manier is goed te zien hoe dat soort halffabrikaten tot stand kwamen.



Als je nog even doorgaat ga ik die keltische en romeinse veiligheidsspelden nog leuk vinden ook!   ;D ;)

mvg/Menno
Groeten,
Menno

Offline timba

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Re: How to make a brooch
« Reactie #2 Gepost op: januari 17, 2008, 00:32:00 am »
Hallo.

Speciaal voor Aureum  ,en ook voor de andere forum leden en bezoekers.

Groetjes.

Timba

aureum

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Re: How to make a brooch
« Reactie #3 Gepost op: januari 17, 2008, 01:42:50 am »
hoi timba

bedankt voor de aanvulling

mvg leon