HS2440 Week 2 Joining metals/ Hammering and jointing Flashcards
What is required for the casting of metals
- crucible (ceramic that can withstand high temperatures)
- requires kilns that fire clays at a high enough temperature
- also furnace technology capable of melting the metal
- eg cast iron, high melting point, not widely seen until the industrial revolution in Western Europe
Crucible (images)
The simplest kinds of moulds in metal casting
- describe open casting vs piece casting, the different features
- open moulds
- earliest casting techniques, prehistoric times
- no joins along any edges, just the shape of the object
- piece moulds have a solid object with edges where (unless fettled or filed away) you can see the join mark, which is liquid running into a small gap
Describe Cored moulds
- mould made in the general shape of the object
- gap left for the haft, axe handle
piece moulds (image)
Evidence of piece moulding in china
- early complex casting
- can be used multiple times
- finishes were artificially produced using chemicals
Lost wax casting
- a clay core, the shape of the object
- covered with wax and then carved
- pins pushed into clay core (chaplets) (usually iron) to hold clay core in place when wax is burnt out by molten metal
- bake the clay and molten wax comes out
- evidence: check for dents/ marks caused by chaplets
lost wax casting: how to prevent air bubbles
- ## preheat the mould to stop the metal solidifying too early, prevents imperfections and air bubbles
direct vs indirect wax casting
- direct destroys your carved statue
- indirect takes a mould of an already made object to create a replica
diagram of a statue being cast in multiple pieces
diagram of lost wax process: multiple castings from one model
How can we see evidence of the lost wax method through x- radiography?
- see the clay core, and the crack running through it
- see remaining chaplets
differences between fire gilding and oil gilding, and processes
- fire gilding, most effective, using amalgam of mercury and gold, the mercury evaporates. is intense in colour and lasts better
- oil gilding uses a drying oil to attach the gilding, more fragile in terms of longevity
- gold is malleable and can be attached to the surface easily
Image of chemical patination and natural patina
Diagram of investment casting
- wax injection attached to a wax core
- shell building technique, spraying on a ceramic mixture, creating a shell in several layers
- molten metal poured into thin shell to produce shapes
- is then knocked out and can be reused.
Alloys of copper and how they are made into objects
Describe annealing process
- sheets of bronze or copper
- using a range of differently finished hammers eg curved edge for raising and indenting metal
- copper is malleable can be thinned and raised
- using a mandrel to smooth out the object
- copper becomes brittle as it is hammered
- distorting and flattening/ stressing grain structure, leads to cracking
- annealing means heating up, releasing stress and reshaping grains to reduce brittleness
example of lockseam (image) and soldering
diagram of lead tin solder
diagram of tinning, forming an inter-metallic compound (image)
- bonds onto the surface, forming a compound
- very durable finish
- seen by a scanning electron micrograph
Lead and tin alloys
