On the excellent suggestion of one of the forum members here I am going to try stainless steel measuring cups ($8 on Amazon) for a diy waiven reflector. That said, stainless has around a 70% reflectivity which really isn’t all that good.
To fix that I was looking into silver plating the cups once done (+95% reflectivity). Is there an inexpensive way to go about this? Add to that, how do you keep it from tarnishing, and can one still solder the waiven to the pill?
Somebody here on BLF found a spray-on mirror coating in their local DIY store, although I don’t remember the details.
Was it VOB who posted the link?
Yeah, fiicr it, either.
I found a spray-on mirror coat, but it is made to go on the back side of glass to make a mirror. One would have to find or make a hemispherical glass dome, then coat the outside of it to make a ‘Wavien’ collar. IIRC, that’s how ‘real’ Wavien collars are made anyway (but with better coating than spray-paint).
https://www.amazon.com/Rust-Oleum-267727-Specialty-Mirror-6-Ounce/dp/B01M03SLQG
is for glass, so if you can get a spherical Christmas ornament or something…
I’ve made my own colloidal silver, and it can “plate out” on the glass coffee-pot that I use. Looks ugly on the inside, but from the bottom, it creates a beautiful perfect mirrorlike finish.
Same principle, I imagine.
How much would you charge to make a few mirrored domes for us? :innocent:
I’m pretty certain you have to coat the inside surface for the best reflectivity. Coating the outside will give you a “mirror” but since the light would have to travel in and out of the glass the efficiency would probably be worse than the bare stainless steel.
Amateur telescope makers have been making their own first-order surface mirrors for a long time (including grinding their own spherical and parabolic reflectors and lenses - by hand!) so it may be helpful to Google that… For electro-formed reflectors, they (the manufacturers I’ve seen) list aluminum as the most reflective but most delicate of their coatings, and rhodium as a good balance of reflectivity and durability. I have successfully polished an aluminum measuring cup/baking dish to a pretty good surface, but it requires removing the anodized layer and sanding progressively with grits from 150 to 3000 before doing any polishing.
If you look at projector bulbs the coating is in the inside. Unfortunately they use either a parabolic or ellipsoid shape.
Even with a coating, the surface must be polished, since any imperfection would be telegraphed onto the coated surface.
People make DIY mirrors for astronomical telescopes, too - they make a glass blank with the right curvature, then chemically plate it (I think) with the reflective coating. That might be another idea to investigate. However they do it, that technique must produce a quality reflective surface on the inside of the curved glass.
I know first order reflectors are better. But the spray-paint mirror coating doesn’t work that way. That’s all I was saying. For a first-order mirror, some other option would have to be used.
EDIT: I have a burned out short-arc projector bulb that uses a hemispherical reflector on the back side to recycle backward travel light waves to the front. It has some kind of special surface, probably for maximum reflectivity.
Is the Wavien reflector behind glass? Typically optical quality reflectors have the reflecting surface on the “front” side of the mirror to improve quality.
From my research silver is highly reflective and stainless can be coated by first coating with copper, then the silver
They actually do this with broken pieces of ceramic tile and coarse cerium oxide. Doesn’t look like a lot of fun to me.
I’ve thought about just machining an aluminum billet to whatever dimension I’d need. 2000 series aluminum machines and polishes really well…
I cut an aperture on the parabolic reflector of one projector bulb by chucking a diamond wheel in a drill press and going around the glass, real slow. Cut pretty easily…
Eep! Y’know how long it’s taking me to just solder the wires to some fake-load resistors for my LED turn signals? At least I did the rears, but still need to do the fronts.
I’m lucky if I can find the time to scratch my bum. That, and all the time I spend here…
And I really really enjoy scratching my bum…
I actually tried, unsuccessfully, to cut a coated glass Christmas tree ball, but it was so fragile. I think if I had seated the entire ball in Play-Doh or such it would have been easier. I was thinking of using PlastiKote on the outside to reinforce it once cut, but never successfully cut one.
Maybe doing the outside first (to get the mirror-finish on the inside), then coat the outside in epoxy resin, maybe with a swatch of gorilla hair.
The balls are already plated so no need for reflective coat! Great idea though on pre-coating the outside. Maybe use fiberglass sheet and resin, before cutting…
Are you saying that the existing coating on Christmas balls already makes the inside a mirror? I would have thought not. Interesting!
If you get the glass ones. The plastic ones are opaque… unless you get a clear plastic one and coat it yourself. But I suspect the inner surface is not as good as the glass ones. Even the colored glass ones are chrome on the inside.
