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24256Re: [atm_free] Coaters

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  • zoran stojcevski
    Nov 17, 2013
      I checked a bit the Texereau book. On page 269 is shown the mirror surface of highly well polished mirror after chemical silvering. The defect are 60 nanometers. That means peak-to-valley error is already 120 nanometers, almost approaching 1/4 wave. Yes, this are mirror surface and not the mirror figure defects, but still.... not acceptable for me, even as amateur. Also, Texereau says further polishing of the surface should be applied, probably the silver coating to be smoothed further. Everybody who is capable of making 1/10 or better mirror I think should be shame to opt for silvering and ruining the surface of that good mirror.
      I think better idea is first to be applied small area of the mirror with silver to be seen how the silver will be deposited - good or bad. Microscope capable of 500x will be enough one to check the quality of the surface and the deposition.
      Mike Clemens did what he MUST do in his case - to apply silver. Anyone can imagine how much money and job and stress and other problems will cost sending that mirror for aluminizing - renting forklifts, mirror is not insured and you risk losing the mirror if something happen during the shipping and during the aluminizing, etc. Definitely anyone who has bigger than 1 meter mirror will opt for silvering. I hope we will hear soon how the mirror perform.

      On Sunday, November 17, 2013 10:21:38 PM, Peter Chen <peterchenmd@...> wrote:
      Re: Silvering

                 I'd like to chime in here, if I may.  The Peacock Lab stuff is really easy to use. Just follow directions.
                Distilled water is cheap, less than $1 per gallon last time I saw it at Wal-Mart. Use liberally for rinsing and cleaning as well.
                 To remove old coating, just use laundry bleach.  The silver comes off easily. Wipe under tap water with soft cloth. Rinse thoroughly with distilled water.

      P.C. Chen

      On Sun, Nov 17, 2013 at 9:37 PM, Mike Coslo <mcoslo@...> wrote:
      Looking for a place to chime in here, this is as good as any.

      When I finished polishing my first mirror, a 12.5 inch, I wanted to do an extended star test, but I also wanted to use it and enjoy it.

      So I silvered it. There is a writeup of what I did on the web somewhere. I still get occasional questions from people who have seen it.

      Here’s what I know.

      You’ll probably need a few tries to get things right. It is not difficult, but there is a learning curve. I silvered the inside of a beaker a few times accidentally.

      Everything has to be as clean and dust free as you can make it

      Clean. Having the mirror surface as clean as possible is the absolute key to success. You might be tempted to eliminate the nitric acid cleaning step, and go with acetone and other cleaners. As they say in Brooklyn fuggidaboudit!

      I ended up doing a multi step cleaning, ending up with the dreaded nitric acid cleaning of the mirror. Several times, until I would stake my life that it was clean enough, then did it several more.

      The chemicals are corrosive, make sure the dam you put around the mirror will handle that.

      Another important part is that the silvering process happens pretty fast. Your best bet is to refrigerate or ice bath the solutions before  you combine them for the final step. This helps slow the reaction down, and you won’t silver the inside of your glassware immediately.

      The result is like magic. The old tomes say to polish the surface with rouge after it dries. I did not, because it was fine as is. Not sure why, but that kept the chances of scratching down.

      It was gorgeous, to use a technical term. Star testing went apace, and I had enough tests to negate the effects of viewing conditions.

      How long did it last? I kept the original silver surface for a year. It was still useable, but I wanted to have a new surface on it to go to a star party.

      I did take care of it - kept the mirror away form the inside of the house. Cooking foods are nasty for silver, and why Grandma had to polish the silverware so often. Coal heat is bad also.

      In the end, I didn’t get much tarnish, but the silver seemed to be almost fading away, and pitting in some places.

      I think everyone who is comfortable with hazardous chemistry should try silvering at least one mirror. If you aren’t comfortable, or a rank newb, you should have some assistance.

              - Mike -

      On Nov 17, 2013, at 11:56 AM, Joe <nss@...> wrote:

      > To anyone that has done this silver process, and left it un protected. IE: Bare silver. There has been posted many timelines as to how long it lasts.
      > OK, cool.  Now just as an experiment, before re coating, have you tried to remove the oxidized layer? using something like "Tarn-X"? they claim that it ONLY removes the oxidized silver, and will not touch the non oxidized silver.
      > I wonder if this could extend the life of the coating some?


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