Make your own silver plated reflectors and first surface mirrors

[chevy1965usa]

While pondering the cost of getting my reflector silver plated, I remembered a chemistry experiment i did in high school. We silver plated some nickels with low current and a solution of silver nitrate.

This got me going, so i headed over to the local high school and talked to the chemistry teacher about this. It was great he actually pulled out a power supply of some sort and a small piece of steel and plated it right there in front of me. It was mirror like with only a wipe with a cotton rag.

This is all it takes. You need a power supply that can provide 3 volts and about .02amps per square cm of material. You can get solutions of silver nitrate online at many places for under 25 dollars. The item you want plated is the negative and use a small piece of silver wire for the positive. Put the silver solution in an inert container and suspend the item in the solution as well as you can. Attach the negative to the item and the positive to the silver wire. Place the silver wire in the solution along with the item and put the power to it. Leave it going and check the plating until it looks like a pure silver surface. Some buffing will be needed but not much.

Not only do i think it will work for my reflector but i also think it could work for a first surface mirror of sorts. But not sure it would be any better then the mirrors you can get from the DIY company's. But will work really well for metal reflectors. I remember reading a post by guy about how he paid 45 dollars to have his reflector plated but got a 22% increase in light output.

Well thats my 2 cents worth. Hope this helps people keep there projects as DIY as possible.

What do you think?

[superdaveumo]

I was reading about silver nitrate and saw that it darkens with exposure to light and oxydizes. Does the electrolysis procedure remove these properties of silver nitrate?

In other words, when you plate something with silver nitrate using the zapping technique, does the resulting reflector / mirror oxydize or darken over time (due to exposure to light and oxygen)?

[Stocker]

Considering the cost, a weekly/monthly/annual/as required buffing would be a good solution to that, just make the reflective part easily removeable.

[chevy1965usa]

When you plate the material it turns out to be 98-99.9% silver. So it would only oxidize as much as maybe a silver spoon or something. Although it would probably oxidize a little faster since its being heated.

[TriodeGuy]

I recently did quite a bit of research on chroming and one thing I learned is that the slightest imperfection or scratch will show through the plating. Don't know how much this applies to plating with silver though but from what i've read it sounds like you have to polish your substrate to an almost mirror shine before you can apply your mirror finish.

[chevy1965usa]

TriodeGuy:
I think your right about needing a perfect surface. But good thing for me the reflector im using all ready has a polished surface. So a good coating of silver should just increase light output. This is assuming that the material being coated is stainless steel, which it is.

I cant find the post, but i remember someone saying that aluminum was more reflective then silver. This is only true for wavelengths under .4 micron. In the visible spectrum from .4-.75 microns silver goes from 94 to 99 percent reflectance. Where as aluminum goes from 92 to 88 percent reflectance. Aluminum performs even worse in the infrared spectrum. Which will only heat the metal more and possibly make it non spherical. So i think aluminum is out for that. At least cheap thin aluminum.

[TriodeGuy]

Sounds like you've got a good plan. If you go ahead with this make sure you post your results, i'm really curious how this will pan out.

I ran across the info on plated surfaces needing to be highly polished on a Caswell's plating forum. There were a bunch of guys there who were griping about not being able to polish out fine scratches regardless of how fine the grit of the compound they used. Another guy there posted this link...

nasatech

Ironically, the link describes a process for polishing aluminum to optical quality using india ink.

Don't know if this would be of any help to you, but it's an interesting read nonetheless.

[pinkmouse]

Originally posted by chevy1965usa
Aluminum performs even worse in the infrared spectrum. Which will only heat the metal more and possibly make it non spherical.

Wrong way round!

Heating the substrate will have little optical effect, but getting the IR out of the beam makes cooling further down the line far easier

[chevy1965usa]

Wrong way round!

Not so sure about that. Take a look at this page.

http://www.sorl.com/opticaltips/coatingreflectivity.htm

I could be wrong as i am no expert and am just relying on chemistry and physics classes taken in high school and collage.

There is also another strange effect that takes place with respect to reflectivity and metal temp. All metals loose there reflectivity has they are heated. The reasoning behind this is a bit to complex for this discussion. But if you heat a metal from room temp to 1000C (if it can go that high without melting) the reflectivity of the metal is cut down by one forth its value at room temp. If my memory serves me correctly the factor that represents this reflectivity change is constant as temp goes up and also constant(almost) when compared to other metals. So if one metal stays a significantly cooler then the other then you should theoretically have better reflectivity.

Although, i think im getting to picky about this, im really just mentioning it because i like thinking that my schooling wasn’t a complete waste (all except my CS classes). Bacuese obviously the inglish clsses dednt hlp.

A really good friend of mine is a electrical engineer and is working on a power supply that will work for a varying range of different sized items. I will be posting pics as soon as I get some silver nitrate to test with