Silvering testing continued

I tried something that should have occurred to me before now: using multiple layers of paint.  Obviously.  I get a much smoother, shinier surface with multiple coats of primer and chrome paint, 2-3 layers of each.  Now it's looking like a mirror.  It's still a very, very poor quality mirror (this brand of chrome paint will not result in a smooth chrome surface regardless of substrate smoothness) but it's reflecting more light and focusing light more sharply.  This is very encouraging.

Silvering test

I've silvered a couple of test objects.  They work as parabolic mirrors, although the main goal here was to improve my silvering technique.  The results are good enough that I think I'm ready to move on to fabricating a hand mirror.

Test objects

I printed up a couple of test objects to see how well a 3D printer could produce the substrate for a first-surface mirror.  Just a couple cm long.  Pretty good results, with some concerns.

- slump.  There's a real danger that the mirror will sag while bing printed.  Very bad given that I need soe degree of precision, especially if I'm building an array of small mirrors.  I'll need to take preventative measures in mirror design (vertical support for the curved surface from the bottom up)
- the thickness of the layers affects surface smoothness and slump

Next task: mirroring.  I've picked up some chrome paint.  Chrome paint has a pretty poor reputation for actually producing an even shiny surface so we'll se how it goes.

Material test: aluminized mylar

I'm going to try some small scale mock-ups of paraboloid mirrors over the next few weeks.  First up: aluminized mylar, a thin plastic sheet with an aluminum coating.

I knew that there were some pretty serious disadvantages to using this material, and those turned out to be even more serious than I'd thought.  The only real advantage is cost.  I was able to make my handheld concave mirror for less than $5, and this video by Dan Rojas demonstrates that it's possible to build a concave mirror more than a meter in diameter for less than $25. His method involves stretching the mylar across a frame then applying suction to make it concave.

Caution: do not try this at home.  Fire hazard, blinding hazard.  This isn't just boilerplate. The blinding hazard turned out to be quite a bit worse than I'd expected, and I had thought I was already being a bit paranoid.  I would strongly recommend against copying the techniques I've used here; what I was doing was quick and crude, intended only to get a sense of how the material behaves.