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Electroforming on uniquely shaped mandrels

(-----) 2006
(to help readers better understand the Q&A's)

'Electroforming' is essentially the same thing as electroplating, except that the plated layer becomes the object of interest rather than being just a coating on the object. The mandrel is the removable object upon which the electroform is built. The mandrel could be a stainless steel belt if you're electroforming copper foil; it could a wax drop if you're making hollow gold earrings; it could be an aluminum shape that you'll later dissolve away.

Q. This is my third question posed to the experts, my previous two were answered well and saved me a lot of time so thanks again, and in advance, to any help I may get on this one.

So now that my shop has our electroforming up and running and we've been getting nice consistent results for a few months, the powers that be have decided to do some one-off art and decorative pieces. The problem is one of the pieces is rather large, a bit bigger than lifesize, jack-o lantern. What I need to know is: does anyone have any advice on how to electroform something that shape? it will be open inside like a real jack-o-lantern, this creates several problems with the inside having very low current density as the out side is basically a shield blocking the inside from possibly getting plated at all. Would I let the outside grow then just mask it off and hope the inside plates? I'm at a loss.
So I once again look to the good people here at finishing.com to help an enthusiastic new electroformer who may be in over his head.

John Keen
metal shop - Chester, New York

(to help readers better understand the Q&A's)

Auxiliary anodes are small objects connected to the anodic side of the circuit to put current where you need it. They can be made of copper if you are copper plating, but will become consumed; so they are more often made of a dimensionally stable material like platinum-clad titanium.

A. How about using an auxiliary anode on the inside?

Good Luck

Hamilton Solidum
- Mays Landing, New Jersey


A. Forget about masking the outside for a two step deposit. What you need to do is put an auxiliary anode in there with a separate rectifier so that you can control the current. You also need to get agitation in there like a bubbler tied to the anode. Good luck, you're going to need it!

Russell Richter
- Danbury, Connecticut, USA


Q. How would I go about using an extra anode? Would I suspend it inside? If so,how? We use rather large copper bars as anodes and I don't think I could possibly fit one inside. Could I use something else as an anode? A smaller piece of copper or even copper wire? and conform it to the inside shape? thanks for the advice so far. And thank finishing.com for the help.

At the risk of turning into an editorial ... I use this site a lot to help troubleshoot and often don't even submit questions. I just read related topics in the letters library. But, man, it burns me when I see people respond with disrespect after someone tries to help them with their problem. If one doesn't like someone else's suggestion, why did one pose their query publicly to begin with? ah....off topic. Anyway, all the help is, indeed, appreciated.

John Keen
- Chester, New York

September 2013

Hi John. You are on exactly the right track, but electroforming specific pieces is somewhat of an art, so the advice is general rather than detailed.

Yes, if the object you are making is copper, you can use copper wire or shapes for the anode. If you were making multiple pieces you can make the auxiliary anode out of platinum-clad titanium so it doesn't dissolve. As Russell notes, you're going to need a lot of luck and/or practice for something like this.


Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

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