Subject: Silvering Process (mirrors)

From: [email-masked] (Don Berry)
Date: Mon, 29 Apr 1996 10:21:38 -0400

Several folks asked me to post this description of how to silver glass
(i.e., make mirrors.)  Here it is.

BTW, I originally posted that Steve Raynor's original warning about silver
solutions was somewhat incorrect.  I hope I wasn't the "
interesting/insulting flame" Steve mentioned later.  My point was simply
that silver nitrate solutions are stable indefinitely; it's silver
solutions CONTAINING AMMONIUM HYDROXIDE that become unstable.   

Also, the silver films deposited by this method should probably be
protected from scratches and tarnish/oxidation with paint, laquer, etc.  

This is my first contribution after lurking here for a while and learning
quite a bit.  I hope people find this useful.

-Don Berry
[email-masked]

------
>From  old notes from a glass blowing class (similar to procedure I found in
an old CRC)

     Brasher Silvering Process

Prepare 3 solutions:

A.  50 g AgNO3 in 2 L distilled water
B.  90 g KOH  in 2 L distilled water
C.  7.8 g dextrose in 100 mL distilled water

Will also need concentrated NH4OH

The article to be silvered must be VERY CLEAN and completely
free of traces of organic materials (e.g. finger prints,
grease, etc.)  Avoid cleaning with dichromate; hot detergent
works well, but must be COMPLETELY rinsed off.

After the article has been cleaned and rinsed it should be kept
moist with distilled water

The silvering solution is prepared from the above solutions
in the following amounts:  16A + 8B + 1C.  Measure solution A
into a beaker and add conc. NH4OH dropwise until the ppt. which
forms just dissolves.  Avoid excess NH4OH.  Next add solution B
and a dark brown or black ppt should form.  If the ppt is light
brown or green, discard and start over again.  Add more NH4OH until
the ppt almost, but not entirely, re-disolves.  DO NOT LET THIS
SOLUTION STAND AROUND TOO LONG (it will become dangerously unstable
upon air oxidation; don't keep overnight.)  Finally add solution C
and immediately pour the mixture into (onto) the article to be
silvered.  Vigorous shaking of the mixture produces a better film than
allowing the solution to remain still.  It is sometimes advantageous
to wash the article in solution C, leaving the article wet prior to 
adding the silvering solution.

After silvering is completed, carefully rinse the excess silver ppt.
>from  the article several times with distilled water to prevent staining.
A final acetone rinse may be used to dry it.  A second coat of silver
can be applied if desired, in which case DO NOT dry with acetone between
coats.  While wet, the silver coat can be easily rubbed off, however,
when dry it becomes semi-permanent.

---

From: [email-masked] (John M. VerBurg)
Date: 2 May 1996 07:25:46 GMT

Don Berry ([email-masked]) wrote:
: Several folks asked me to post this description of how to silver glass
: (i.e., make mirrors.)  Here it is.

[snip].

This is really  funny. I just got done make two quartz dewars using this 
process. In case some of you want the actual reference, The book is called:

"Scientific Glassblowing" by E.L. Wheeler. It's been around for quite 
awhile and should be available in any University library.

I just want to add some useful information based on my personal experience.

CLEANING: I used a 30 minute wash of cleaning solution (10g sodium 
dichromate in 200ml of concentrated sulfuric acid). at 60 C. Don't 
substitute potassium dichromate for the sodium dichromate. It's far less 
soluble.  Rinse 3x with distilled or deionized water. Then wash with 
concentrated nitric acid for 10 min. Rinse 3x with distilled water. Wash 
with concentrated ammonium hydroxide. WARNING. All of the above chemicals 
are EXTREMELY CORROSIVE, if you don't know already. The cleaning solution 
is corrosive, dehydrates the skin, and is carcinogenic.I would recommend 
woking in a fume hood along with goggles and gloves.
	 The mirrors I made using this preparation and the Brashear process
 came out beautifully. 

IN CASE YOU SCREW UP (removal of mirrored surface):

Make a 5% solution (wt/wt) of cupric chloride (CuCl2) and fill the 
silvered vessel. The mirror will turn a pinkish color. Wash 2x with 
distilled water. Prepare a 10% of sodium thiosulfate, also called sodium 
hyposulfite. Fill the vessel. The pink film should dissolve. If there is 
some left on the glass, repeat the process. Rinse 2x with distilled 
water. Wash with 10% sodium hydroxide to neutrillize the previous 
solution. Rinse 2x with distilled water. Now you can try silvering the 
surface again. 

John Verburg - Graduate Student 
Dept of Chemistry 
Indiana University
Bloomington, Indiana USA

DISCLAIMER: The above is for informational purposes only. I cannot be 
held responsible for any injury resulting from improper use of this 
information.

---

From: [email-masked] (John M. VerBurg)
Date: 2 May 1996 07:39:42 GMT

Oh yeah,

In case any of you want the gory details on the whole process including 
the mistakes I've made, substitution of chemicals, and how to tell if 
your solution is ready, don't hesitate to ask. I would be more than 
willing to share my experience.

John VerBurg - Graduate Student
Dept of Chemistry
Indiana University
Bloomington, Indiana USA

---

From: [email-masked] (Terry McCreary)
Date: Thu, 02 May 1996 17:17:45 GMT

>(i.e., make mirrors.)  Here it is.
 <snipped>

Regarding sources of chemicals for silvering:  check first with your
local high school chemistry teacher, and bring the silvering procedure
with you.  You might interest him/her enough to actually do the
procedure there!

Or see if the nearby university has a stockroom that will sell the
chemicals to you.  Again, bring the procedure along and explain what
you're trying to do.

If neither of these works, the back pages of Popular Science lists
chemical vendors that will sell to individuals.

Incidentally, an alternative procedure I mentioned before is the
Martin method.  It can be found in "How to Make a Telescope", J.
Texereau (either edition).  It's rather long and I prefer not to
violate copyright laws by posting it here, but the local library (if
large) should have a copy on hand.

Finally, vacuum aluminizing doesn't tarnish, lasts longer than silver,
and isn't that much more expensive for small mirrors.  If it's
feasable to aluminize the object, check "Astronomy" or "Sky and
Telescope" magazine for sources.

T. McCreary
"I don't need a disclaimer.  Everyone knows that I don't know what I'm
talking about."

---

From: [email-masked] (LEE WARD)
Date: Thu, 02 May 96 21:52:00 -0600

I saw the mirror process ob cable tv and you just Soak mirror in
Muriatic acid for 2days then wash off and rinse with water,THEN rinse
with DE-IONIZED water,then Spray the silver solution onto glass and when
dry Paint Backside of glass with latex paint! Voila! Now if i only knew
where to get the Silver solution and deionized water i could be a star!
                              Lee Ward

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From: [email-masked] (Terry McCreary)
Date: Fri, 03 May 1996 16:55:48 GMT

>where to get the Silver solution and deionized water i could be a star!

Muriatic acid is hydrochloric acid, available at many home/hardware
stores; used for etching concrete.  Deionized water is water that has
been passed thru a special column that removes dissolved ions.  It's
usually a bit purer than distilled water, but good quality distilled
water is an acceptable substitute for this work.  Or pass distilled
water thru one of those little "purifiers" used to make "clean"  water
for filling the wife's iron.

Good luck,
T. McCreary