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On 10/18/18 10:14 PM, Matthew Sweeney wrote:
I would much prefer to find a nice wood or plastic form to use, but haven't
had much luck finding a source of cheap rings, spheres of various sizes.
The polystyrene forms I found are fairly dense and I actually want to make
these items quite light if possible.
Time will tell if it works :)
There have been all sorts of interesting ideas proposed in the past..
It's hard to find them in the archives, because there's no obvious
search term..
Here's some ideas:
Spheres are easier
- cheap globes can be painted or metalized
- garden gazing balls - they can be hard to drill/cut
- floats & buoys
- large glass or plastic carboys
- spherical pressure tanks of various kinds
Toroids are harder
- tire inner tubes
There's plenty of discussion about various ways to do papier mache or
plaster of paris or fiberglass over some form, and then you're faced
with the problem of a conductive coating.
As Antonio pointed out, for a lot of applications the coating does not
have to be particularly thick, just smooth & conductive, so spray on
aluminum paint might work fairly well. I used to have a can of flat
black spray paint that clearly used carbon black as the pigment, so it
was quite conductive.
You can go to a paint store and ask them about mixing a custom batch
with aluminum powder, and then you'd use a standard air spray gun (e.g.
Binks gun) to apply it. Ask about "gilding"
you can also do traditional gilding with thin metal sheets - gold is, of
course, traditional, and makes a very nice smooth mirror surface, if
applied upon an appropriate substrate that is strong enough to burnish
the gold.
(a quick amazon check shows 0.12 square meters (1120 cm2) of gold leaf
is about $15, so covering a 50 cm sphere would be about $150.)
There's also thin aluminum and silver sheets.
You can also call around to shops that do evaporated metal deposition -
you can get almost anything covered in a metal film of your choosing -
how do you think they make those cool mirrored sunglasses, after all. If
you're not picky about even-ness of coating, it's a lot cheaper - the
sunglasses folks want just the right thickness and it has to be even.
There are also specialty plating shops that can plate almost anything -
I've seen all manner of things (including things made of wood) plated -
think about bronzing baby shoes as an example.
Although, overall, conductive spray paint is probably easiest.
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