MIMF

That's cool, Alan! Please post something of the results.

Alan,
You may find making molds with the silicon as addictive as guitars.

About ten years ago I did a bunch of climbing holds when we were putting up a climbing wall at the local YMCA. Tried several mold materials and the silicon, while not cheap, was by far the best for that use. Easy to remove the resulting part, and the mold would last forever. We mixed sand with resin to make the holds, and I thought it would tear up the molds fairly quickly, but it worked really well. Obviously didn't have to worry about bubbles etc. for that kind of a part, so didn't need to do any vacuum, etc.

One thing I still remember is how incredibly detailed the surface of the mold could be, It sometimes reproduced fingerprints in the subsequent parts, so make sure your master is cleaned up pretty well. What you see (and lots of what you didn't see) is what you get.

i'm hoping to do some vacuum bag work myself pretty soon

I used to have an 18" x 18" vacuum forming machine, it used an electric element much like your stove. Plastic sheet was suspended above the part mold. The heater element swung back after the plastic had reached the proper melt temp. You would judge this by watching the plastic– first it would sag way-down, wait, then it would tighten up. It was when it looked like it wanted to sag again, would then slam the plastic frame down on the mold and hit the vacuum pedal.

We made smaller frame adapters to hold smaller sheets of plastic so you didn't blow an 18" sheet on a 3" part. We also moved away from positive molds to negative molds that we would ram an assist block into the back side of the molded part, to really capture mold detail. Downside, negative molds are more difficult to make.

When I was in design school, we would scour the yard sales for one of these Mattel toys ---- http://www.spookshows.com/toys/vacuform/vacuform.htm

How does one pull the plastic into a negative mold, David? Are there tiny venting holes in the bottom corners or something?

Atmospheric pressure will "push" out all the air from the negative mold without the need of venting. The beauty of vacuum is that it works in all directions and is why vacuum forming and clamping is so effective on complex surfaces.

(Alan Carruth) One of my students is restoring a circa 1780 English guittar (yes, that's how its spelled). It's a ten-string cittern, with interesting tuners: there's one on my web site. This one was used for parts in restoring another, and now he wants to restore this one as well to use in playing duets. The rose in it was used for the other instrument. It's an open work casting, depicting (I guess) a shepherd and his lass, that was probably made from master that was hammered up from thin sheet. It's beyond my skill to duplicate it as a carving and get the style right, so we're going to try to make a mold using the original as a master, and electroform a copy. We're just at the beginning of the process, with a lot to learn. As far as I'm concerned, that's one of the best things about my job.

We had a mini discussion about roses and so forth after the main GAL lecture this summer. They are very thin, usually brass or possibly tin. They are particularly tricky to get in and out of the instrument.
Electro forming is an interesting process where you deposit metal onto a non-metalic mold that has been first treated with conductive paint. At that point it's just like electro-plating where the electrons flowing through an acid bath carry and deposit metal from a sacrificial bar over to the part you are creating. It's something model makers use a lot to create small, detailed sheet metal parts starting from a plastic part. It's also the way you can chrome plate plastic trim on a car etc.

Jewelers use electroforming to make metal leaves and such, and, of course, there are those bronzed baby shoes....

David, was Doolin part of that conversation? He had an article in AL about anodizing aluminum, but maybe that's something entirely different.

So, what you're saying is it would be possible to chrome my pickup covers? That'd be frickin' awesome!

Jason, I don't believe Chromium plating is a DIY process; but you could nickel plate them, or have them Chromium plated by a professional plating service.

MicroMark sells plating stuff, including something they call 'copy chrome'.

Rio Grande jeweler's supply carries plating chemicals and equipment, but I didn't see any chrome. Some of the more exotic stuff contains cyanide; reason enough to avoid it in my opinion.

Both put out very dangerous catalogs, full of stuff you NEED...

Caswell is the grandaddy of the DIY plating world. Some if not all of their formulations are designed to be neutralized so they can be safely flushed down the toilet or so they say. I'd suspect you would want to gather up any precipitate before doing that or better yet boil away all the liquid and take the dry components to your local waste transfer center for more appropriate disposal. Of course they can take liquids too so that you won't have noxious fumes billowing around your house.

My wife already things that the stink coming off the hot plastic is nuking my brain, so maybe I'll skip the projects that result in actual hazardous waste.