Kia ora. Would some kind person please tell me a) what photopolymers are and b) how are they used in the making of jewellery? It sounds that they might be used in casting, I think.
I know - I’m higgerent, but I do live in the wopwops (boondocks to Yanks!)
/\
/ / John Burgess
/ /
/ /__ johnb@ts.co.nz
/ / \ \
/ (___)
(_________)
Hi John
I can’t give you a technical answer, but I can give you an idea of what
photopolymer material is.
The main way photopolymer material comes to jewelers is in the form of a
printing plate used by printers for printing on odd materials. It is
available in thicknesses ranging from about .2mm up to 2mm or larger and
comes with either a polystyrene or sheet metal backing. The photopolymer
material itself comes in different hardnesses. It is commonly water
soluble now (used to only dissolve in flammable solvents) and hardens to
relative insolubility by exposure to strong ultraviolet light. A film
negative is commonly used to mask the areas to be etched. The results
are a bit like the magnesium plates from photo-engravers. The
polystyrene backng can be removed after etching to produce a fully
pierced flat model, and by using double exposure techniques, a double
level etch can be created, producing a pierced model with etched
details, like a pierced out letter of the alphabet with raised borders,
interior scrollwork and a textured background. The metal backed material
can be molded using RTV mold rubber. It’s a bother to cast as the steam
created in the burnout process tends to etch the model further, and the
expansion of the material can crack or otherwise damage the investment.
This problem can be gotten around using the super hard phosphate bonded
dental investments designed for flaskless casting. This type of
investment needs to be removed with a hydorfloric acid substitute
(forget the hydofloric acid, it’s too dangerous) that’s available at
dental supply houses.
The industrial applications of photopolymers involve using a liquid
solution in a tank. There is a platform in the tank that progressively
moves downward. A 3-D pattern is built up in successive slices by the
action of the descending platform and a laser playing across the surface
of the vat defining each successive slice of the pattern. I realize that
this explanation is hopeless but so is my brain! 
I have heard of a
very advanced process in which twin lasers shine INTO the vat hardening
the liquid material only where the laser beams cross. I remember all the
hoopala when Boeing demonstrated this (now old) new technology.
Nowdays, there are machines capable of of building up extremely complex
three dimensional wax patterns (like a basket ring with tube setting and
wires etc…) from a computer file. One such unit is the Sanders Model
Maker. It’s a $55,000 table top unit. The only trick is you have to be
able to create the piece of jewelry in some 3-D modeling program, which
is extremely difficult for most cad programs. I saw one such ring
created by an engineer using Pro-Engineer design software (about a
$15,000 program). Maybe in the near future cad programs will get easier
to use, but I doubt it!
Sorry about the length… I do get carried away…
Jeffrey Everett
Handmade 18K and platinum gemstone jewelry. Fine die
and mold engraving. Diamond setting. Class rings/pins.
25 years experience in the jewelry trade. 515-469-6250
John Burgess wrote:
… Just didn’t want to be First!!!
Jim
At 04:06 PM 10/11/96 +1200, you wrote:
Kia ora. Would some kind person please tell me a) what photopolymers are
and b) how are they used in the making of jewellery? It sounds that they
might be used in casting, I think.
That is the first … Wopwops’er!
Jim
At 04:06 PM 10/11/96 +1200, you wrote: