Mirrors

This page is a collection of items I have collected about mirrors and silvering glass objects. I have not yet done anything with mirroring, although I would like to. Please note that modern serious mirrors (astronomical) are made by applying aluminum in a vacuum chamber, so the techniques on this page are for scientific and art glass, like insides of Dewar vessels, thermos bottles, gazing balls, door handles, and ornaments. Please note that a long time ago (200+ years) mercury was used in certain glassware so it is still called mercury glass although all recent mercury glass is made by depositing silver from solution. Mercury is not now used and is very dangerous to have around (as in dribbles on the floor, etc.) because the vapor does damage to people. Also note that the acids involved are serious acids that will do serious damage. [edit 2008-02-13]
 

Ordinary Mirrors

An ordinary flat mirror is made by taking good quality glass and coating the back with a thin coating of shiny metal, usually silver today.  Then the coating is covered with an opaque paint, usually black, to increase the reflection and that is coated with a decorative paint, often grey, that is easier to clean.  Old mirrors often have engraved details in the glass making them worth preserving, but the silvering has been damaged, usually by moisture penetrating the coating.  Removing the coatings must be done carefully to avoid scratching the glass. 2006-08-21

Color of Mirror
It depends on the color of the glass and of the reflecting surface.
Most glass sold today, including that used in mirrors, has small impurities of iron oxide which give it a slight green color which can be easily seen by looking in the edge - like stacked glass at the store. It is possible to make totally "white" glass as it is called in the industry, but it still costs more.
Most mirrors are silvered - a thin coat of pure silver is chemically deposited and then covered with opaque backing paint. Silver has a very slightly warm tone because, as the other answers mention, reflection involves taking light photons and firing them back, with silver hanging on to a few more of the "blue" end of the spectrum, as does the green tint.
The other common reflector material is aluminum applied as a vapor in a vacuum chamber, as is done on astronomical mirrors, and some flat mirrors, and aluminum reflects more evenly across the spectrum so, to most people's eyes, looks "whiter" than a silver mirror.
It is possible to tint both the glass and the metal or to use metal alloys, produce more distinct color toning, such as a pink mirror by addition of gold.  2012-08-22

Value of Silver
Recently I was asked if the silver on a large heavy old mirror was worth salvaging.  I had not done the calculations before and found it a good exercise to look up the possible thicknesses of the mirror coating on the Internet and compute how much silver there was and what it cost.  Working backward in one sense I found that the the silver spot price these days is about $15 per ounce and a cubic inch of silver is about 6 oz.
Finding the thickness of silvering on mirror was harder than I thought it would be but this http://adsabs.harvard.edu/full/1911PA.....19..398C older reference says that after a year the silver was dissolved off a 5 foot diameter astronomical mirror silvered by the Brashier's method and found to be equivalent to 1/280,000 inch thick "400 grams of silver nitrate used in depositing silver laid down 1.7 grams of silver".
If a larger round number, say 1/100,000 inch, were used for estimating then a cubic inch of silver would cover 100,000 square inches or just under 700 sq. feet with $90 worth of silver  - so a huge 7x10' mirror, 70 sq.ft. would have about $9 worth of silver by this crude estimate and probably less than a third of that.  And unlike a front surfaced astronomical mirror, it would be mixed with a mass of removed paint. Commercial firms can preserve the acid solutions used for removing silver and, like older photography processors, get it refined for the silver. 2009-08-21 2012-08-22 edit

One Way Mirrors/Glass

Glass can be covered with a thin coat of silver or aluminum and then not covered with the paint used to make an opaque mirror. When this is done, the glass is said to be half-silvered or to be a one-way mirror or one-way glass. Because of these latter names, there are people who believe that a product exists which is always mirrored on one side and always clear on the other side, which is not true. The visibility through such a mirror/glass depends entirely on the lighting - those on the more brightly lit side will see the glass as a mirror and those on the darker side as a more or less transparent window. The silvered surface (and reflection) take out much of the light passing through, so the view through the glass is always darkened. If there is any light on the dark side, then it is possible to make out what is going on there from the bright side. Even if the dark side is completely black, some light is present having come through the one-way. Because the reflection is less than perfect, with experience it is easy to spot that a piece of mirror is half-silvered.  Normally, because of its expense and fragility, users installing half-silvered do not even disguise the small mirror as being a real mirror - the reflection merely prevents people from easily knowing whether someone is behind the view port. It is now much cheaper to use reflectorized plastic film such as is used on cars.

Front Surface Mirrors

Normally mirror silvering is applied to the back of the glass where it is protected from touching.  It is further protected and enhanced by painting over the silvering with opaque paint that reduces further the light passing the silver coating, making the reflection brighter.
When silvering is applied to the front of a mirror, it is normally very fragile - it will scratch easily and show fingerprints if touched and if wiped will show smear as tiny scratches, reducing the reflection.  It is difficult to put a protective coating on the mirroring, it must be very thin and clear.
However, there are uses for front surface mirrors because there is only one reflective surface. When the coating is on the back, a faint image is reflected from the front of the glass as well as the stronger one from the back. Whether this double image is a problem depends on the use. Glass makes a very smooth surface for a front surface mirror, better than metal.  The most widely available front surface are the small mirrors sold for use in kaleidoscopes.  Astronomical mirrors are front surface silvered and both curved and smaller flat mirrors are sold through astronomy supply firms although these are more likely to be aluminum deposited in a vacuum than silver. 2005-07-10

Silvering

Link to East Carolina University Site with information

From Ed Brice's column in the Ft. Worth Star Telegram, 2007-04-20, Q:" I have an antique mirror that needs to be resilvered. Is there anyone in the Fort Worth area who does that kind of work?" A:"My pals over at The Edge of Glass Art [9524 Semintal Drive, Crowley, TX 817-297-4404 ] will be able to handle all your resilvering needs.  They also do beveling, carving and other thing that'll slice up your finder if you have no idea what you're doing "

Heck, here are some messages
Subject: Re: MIRROR SILVERING-NEED HELP! From: jriser@azstarnet.com (James P. Riser) Date: 24 Mar 1996 02:45:01 GMT In article <4iq3nl$ai6@usenetp1.news.prodigy.com>, GWUU25A@prodigy.com (Peggy Alcorn) wrote:
> I have waited most of my life for the time to work with mirrored glass, and
> now find that no one does it by hand anymore.
> I am interested in silvering selected portions of glass to enhance stained glass work.
> Is there anyone out there who knows how to do this?
> Peggy Alcorn > PEGGY ALCORN GWUU25A@prodigy.com

Peggy; Silvering is not too difficult. When I worked as a scientific glass blower, we silvered the insides of Dewar flasks all the time (30 years ago). Cleanliness is important! We cleaned the glass with some rather nasty solutions. To silver we used a silvering formula from a scientific glass blowers book. It used a silver nitrate solution and a sugar solution. The silver ends up being deposited on the glass. As I recall, we kept everything agitated to get a good even coat and we used cooled solutions to slow down the reaction. Try looking in a university library for the formula and process. If you can not find it, I'll dig up my old books and look it up for you. Any silver deposited where you do not want it can be removed with acid. Good luck. By the way, do not get the silver nitrate on your hands - it stains! Jim

Subject: Re: MIRROR SILVERING-NEED HELP! From: bartky@mcs.net (Scott Bartky) Date: Wed, 27 Mar 96 11:37:13 GMT
In the Art's and Recipes section of the Handbook of Chemistry and Physics (perhaps older editions -in all the ones I own from my earlier nerd days) there are two separate methods described along with elaborate surface cleaning techniques required before silvering. I might add here it is real silver and not mercury which has never been used! There are two methods described viz. Brashear's Process and Rochelle salts Process the latter depositing the silver more slowly. Both methods were published in: Miller's Laboratory Physics, Ginn and Co. - publishers The Handbook of Chemistry and Physics in 1952 was published by: Chemical Rubber Publishing Co. as of 1952 the 34th edition the oldest I own It is probably into the 50th edition by now. Ask your favorite nerd for the location of the nearest reference library near you.

Subject: Re: MIRROR SILVERING-NEED HELP! From: mcFrenzy <mickey@grfn.org> Date: Wed, 27 Mar 1996 09:47:44 -0500
Silvering is not done with mercury. That was abandoned around the turn of the century. If you find "mercury" mirrors, keep them. They are valuable. I did resilvering at one time. I shall post more information and sources in the near future. It is not hard and can be done at home with the proper tools. Basically it's silver nitrate solution that is mixed w/ a base solution of sodium hydroxide on the glass. Everything combines but the silver which is left behind and deposits on the glass. http://www.grfn.org/~mickey also try this stained glass site http://www.cns.net/pristine

Subject: Re: MIRROR SILVERING-NEED HELP! From: billw@puli.cisco.com (William ) Date: 28 Mar 1996 05:24:47 GMT
>I am interested in silvering selected portions of glass to enhance
>stained glass work.
Check in the library for books on amateur telescope making. There's a process using ammonia, silver nitrate, and (I think) sugar. Aside from silver nitrate being pretty expensive, and the solution tending to "go bad" and form explosive (really!) byproducts if you let it sit, it shouldn't be too bad. I don't know if it's appropriate for silvering a small piece of glass already in a frame - I think its normally done by immersion. BillW

Subject: Re: MIRROR SILVERING-NEED HELP!
From: Gary Borden hebegb@fullnet.net
Date: Thu, 04 Apr 1996 16:25:29 -0600
Sam Gaylord wrote:
> Chuck (sirius@mhtc.net) wrote:
> : GWUU25A@prodigy.com (Peggy Alcorn) wrote: > > :
>I have waited most of my life for the time to work with mirrored glass, > : >- > : > PEGGY ALCORN GWUU25A@prodigy.com > : I would find this information interesting and would bet that there are others out there who would also. Would you please post any answers you find?
I did some silvering 4-5 years ago. It's not really THAT hard to do if you are careful with the preparation of the glass and the chemicals (one being silver nitrate) used to precipitate the silver layer on the surface. I have some literature, procedure guides, and material sources stashed away somewhere around here along with some of the materials themselves, although the chemicals have probably gone bad since. I resilvered a couple of 2-3 square ft. old mirrors for some friends, but mainly silvered several of the interiors of my own handblown vessels. I taught glassblowing, stained glass, and fusing for about 10 years at our local community arts center run by the City Parks & Recreation department (pretty progressive facility to be supported by the city). I'm going to print out this message, and as soon as I can scrounge up the info I've got available, I'll see that you get a copy or the sources to get more recent info. I can also see where this could be a profitable sideline if you've got the shop (garage, basement, etc.) and the time. Check around and tell me how many people within your region are actively silvering--very few, if any I'll bet. If anyone else in this newsgroup would also like more info on silvering, just e-mail me. I'll also try to post a general rundown on the steps involved here when time allows. For the next couple of weeks we're going through some major changes at work, so it may take a week or two. MORE LATER.... Gary Borden ------------------ 

hebegb@fullnet.net 3/10/98 mirror formula site http://www.grfn.org/~mickey
Silvering and Reducing Solutions
1.) 1 pound silver nitrate 24 ounces water 40 ounces ammonia
2.) 1 pound sodium hydroxide 60 ounces water
3.) 1 pound dextrose 60 ounces water

For making silver solutions: 4 ounces from #1, 4 ounces from #2
For making reducing solution: 6 ounces of #3 1 gallon of water
Be sure to wash out silver bottle each time
Try and watch that solutions empty at the same time
In hot weather use only 4 ounces of #3 to each gallon of water *****************************************************
following is a condensed recipe for solutions that are to be used not to be stored.
5-gallon silvering solution: 5 1/3 ounces silver 5 1/3 ounces sodium hydroxide 13 1/3 ounces ammonia
5-gallon reducing solution: 5 1/3 ounces dextrose 1/6 ounce formaldehyde

1-gallon silvering solution: 1 ounce silver 1 ounce sodium hydroxide 2 6/9 ounces ammonia
1-gallon reducing solution: 1 ounce dextrose 3/100 ounce formaldehyde

SILVERING SOLUTION for GLASS ( http://www.dragonbeads.com/silverng.html)

WARNING - use of this is at your own risk - it involves chemicals that should be treated with respect. The writer and this website assume no liability for results.

First method is do-it-yourself - sources for "kits" follow these instructions: METHOD A This is the method we used for years at The University of Illinois. Its a 3 part recipe. I know there are other products out on the market. Because of the use of Silver Nitrate this process can be quite expensive.

A. Silver Nitrate (66.6 Grams) to, One liter of deminerialized water
B. Potassium Hydroxide (140 Grams) to, One liter De-Ionized water
C. Dextrose Anhydrous (65 Grams) to, One liter De-Ionized water/175cc Alcohol
[MF plus ammonium hydroxide in small quantities, see below.]

To do the silvering process:
1. use equal amounts of each solution
2. Solution A add ammonium hydroxide (a few drops) stirring until it becomes clear
3. Solution B add to A and add ammonium hydroxide stirring until it becomes clear
4. Solution C add to and A & B and stir and pour into glassware. The silvering will happen quickly.
5. Make sure all solutions are cold before attempting to silver.
6. Make sure all solutions are in stored dark amber bottles, in a cool place.
7. All water used in making solutions is deminerialized.

I was also taught to let these the A, B & C solutions sit and cure for a week or so in a cold room/refrigerator. Don't let these solutions get warm it will speed up the silvering process and do not use too much ammonium hydroxide as  it will coagulate and ruin the batch. ( I used a dropper or pipette) This has to be done in a well ventilated area for these are very strong chemicals.

Also silver nitrate will never come out of your clothes and takes forever to come off of your skin. Always wear gloves and protective clothing while doing this process.

Jan Singhass Scientific Glass Technology Lab (Shipping) 101 Daniels Hall (Mail Box) 8209 Dabney Hall North Carolina State University Raleigh, NC 27595

Shop: (919)-515-3562 Fax: (919)-515-7668

> ... makes a reference to a "spray silvering" process. A friend
> researched this and found the following URL for the company:
> http://www.peacocklabs.com/products.htm#silveringsol [which worked on 2005-08-07]
> Their process does not involve immersing the object to be silvered in a
> solution as it just sprayed on with an ordinary hand pumped sprayer.
> Three solutions are used and my understanding is that it is very
> efficient and economical. The only downside is that the minimum
> quantities will silver ~200 sq ft.
I have run into this before and have not previously had it on the page because of the risks of spraying these solutions in the air without proper protection. 2003-04-30

REMOVING SILVER

Subject: Re: removing silver from mirrors From: "Wm Kidd" <mrstgls@worldnet.att.net> Date: 19 May 1997 17:42:49 GMT Richard <rww@pitt.edu> wrote in article 337F996D.9A2F1547@pitt.edu...
> Does anyone know how to remove the backing from a mirror and have clear
> glass remaining?
Lay the mirror flat on a protected surface (plastic sheeting e.g. visqueen), backing side up. Lay a few sheets of newspaper over the back of the mirror, and soak them with Sno-Bol toilet cleaner*, or muriatic acid. Let it soak awhile, anywhere from 10 minutes to an hour or more, (the newer the mirror, the longer it will take), after which the silvering will brush right off with a scrub brush, or peel right off with a razor-blade scraper. I remove the silvering from lots of old mirrors in order to use the glass for replacement bevels for restoring antique beveled windows with authentic period matching glass.
*[Sno-Bol toilet cleaner MSDS is, in fact, hydrochloric acid with a lot of warnings around it. Muriatic acid is another name for hydrochloric acid. MF 2010-11-27]

Mirroring Glass Messages 4/16/96
<< Two questions about mirror.
<<Can you kiln fire mirror at low temperatures, without the silvering or the paint melting off? <<i.e. slumping
       No
<<, firing decals etc.,
      Maybe, depending on temp, but probably not.
<< Can you de-silver mirror in selective areas, such as if you wanted
<< a circular mirrored area with a clear border?
      Probably, with a lot of mess. Paint remover for the backing, which will take some of the silver with it, careful removal of the silver with cleaning solutions.

<< If anyone can e-mail me steps to silver mirrors it would be appreciated. >> Check the archives for the group, it was posted a while back. A messy business that would probably be easier than trying to take it off.

Gold Mirror
This site offers a bunch of interesting looking stuff.  Offered as a suggestion of possibilities.
 Aerosol Laboratories (in India, unfortunately)