[Nivea]

Hello,
I am casting hand impressions of a 2 month old baby. I am getting life-like replicas with epoxy and rtv's from alginate molds but I'd really like to use metal. What metal (precious metals included) and process would give a result that wont require polishing? It would be a shame to lose the amazing fingerprint detail.

[Geof]

Have you heard of lost wax casting? I think that would be the route to go but you would have to do a positive/negative procedure first with epoxy and RTV: Cast an epoxy positive from your alginate mold, then a RTV negative from this and make the wax positive from the RTV. Then the wax is coated with ceramic slurry, dried, baked in an oven to cure the ceramic and melt out the wax and the final metal casting is made in the resulting ceramic mould. You can get amazing detail but whether it would extend down to baby fingerprint whorls is questionable.

Google 'lost wax casting' and 'investment casting'.

[USMCPOP]

Not sure if any of these would be suitable:

http://www.hitechalloys.com/hitechalloys_002.htm

[JamesP]

lost wax casting..

[Nivea]

Yes I am familiar with lost wax/investment casting. The issue Im concerned with is the molten metals ability to to conform to the detail of the mold under gravity only. I think it's surface tension is too great. I am told some bronze alloys expand on cooling but I am yet to try it. I may need to look into forced casting?
Thanks for the link, I will look into these alloys.

[Geof]

.... the molten metals ability to to conform to the detail of the mold under gravity only....

.... I am told some bronze alloys expand on cooling but I am yet to try it...

With lost wax/investment casting you increase gravity by using centrifugal casting; used a great deal for jewellery work on both a DIY and business level.

I have never heard of a bronze alloy that expands on cooling but some of the typemetal alloys do. Typemetal also melts low enough that you can cast in silicone molds I think but you would still need to do the positive/negative steps to get the mold.

[Kipper]

Lost wax was made for this...though usually I try to get rid of the fingerprints

[Harryman]

Spincasting with pewter can give you the same level of detail as lost wax with less steps too, I've got extensive experience with both. As with all things casting, the process does not guarantee quality, you tend to have to get some bugs worked out of both the process and the operator.

[Geof]

Spincasting with pewter can give you the same level of detail as lost wax with less steps too, ...

What do you use for the mold in spincasting?

[Harryman]

Vulcanized rubber, either black or silicones are the best. You can also use various RTV rubbers, but they can get pretty pricey and don't last as long.

There's some sites around showing guys DIYing machines and vulcanizing molds in ovens with C clamps. Like most things, it's best if you have the correct equipment, but you can manage with some garage tech stuff.

To make a very low, low tech centrifugal casting system, fill a bucket on the end of a rope half way with sand, submerge your mold, pour it and twirl like a madman. Not recommended indoors for obvious reasons and keep the burn kit handy.

[Konstantin]

Have you thought of a covering the epoxy piece you have in metal by electrolysis?
You could cover it in nickel, like it is used in money printing. I think there is a Discovery Channel chapter about money printing technologies.

Konstantin.

[Ican]

About any metal you cast will need some degree of finishing. Of course, Gold takes the least. Naturally, the higher the karat, the less finishing. Sterling Silver takes a lot of finishing... but you can "pickle" a silver casting and then use an oxidizer and stay away from a lot of finishing. OR... for silver, you can use an electro polishing technique that will almost make it looked buffed and retain all the detail. Hope this helps.

Ican.

PS... Don't forget the castable resins that you POSITIVELY cannot tell from real metals until picking them up... and then sometimes it's hard... and the clay metals that you can push into a mold then cure. I'm gonna write a book!!! Ha!

Hello,
I am casting hand impressions of a 2 month old baby. I am getting life-like replicas with epoxy and rtv's from alginate molds but I'd really like to use metal. What metal (precious metals included) and process would give a result that wont require polishing? It would be a shame to lose the amazing fingerprint detail.