metalized polyfilms


A few on the list have considered building their own rolled or flat plate
metalized polyfilm caps.  I repost the following email about electroplating
polyethelyne films.  I found it on the askjeeves-dot-com search engine which
bundles together and searches four other major search engines.  Searching
key words of "metalized" and "polyethelyne"  turns up huge amounts of
sources for manufactured metalized polyfilms and commercially available

Most commercial metalized film is manufactured by vacuum deposition of the
metal on the substrate.  These films are commercially available.  An
easy-to-build metalized poly film self healing flat plate cap seems a
distinct possibility.



Letter #
From: Plaidhatt-at-aol-dot-com
Date: Tue, 8 Apr 1997

Hi, it is me Eric Keaveny from Harrison High School. I have been doing
research on electroplating polyethelyne. One of the steps is called
"sensitizing" and involves the use of SnCl2. I am not sure why this process
is used or what type of reaction takes place when the plastic is emursed in
this solution. Then I am going to use the Brashear process to deposit silver
on the surface and then plate it from CuSO4. I was just wondering what the
stanneous chloride was for.

Eric Keaveny
Date: Mon, 10 Aug 1998


The present school of thought is that the SnCl2 separates in water and
leaves Sn++ in solution. This then wets to the surface of the subtrate and
presents a "sensitized" surface for deposition of, in this case, silver.

SnCl2 sensitization is commonly used as a precursor for a PdCl2 "activation"
before electroless deposition of Nickel as well.

Maybe you can help me. I am looking for information on the Brashear process.
Do you have documentation on the subject?

Milton Ives

Milton Ives - CiDRA Corporation -
E-mail address: ivesm-at-cidra-dot-com

Date: December 4, 1998

In recent days, I have been collecting information on and chemicals for the
Brashear Silvering process. I have run a few test runs in glass and have not
tried plastic of any kind yet. Some references mention the use of the
stannous cloride and some do not. In my expirement to date, I have not used
it, but will be ording some to try later.

The material I have states that the sensitizer solution has the available
tin ions (Sn2+) that are free to react with and bond to the negatively
charged anions on the glass silicate surface. (I do not know if this applies
to other surfaces such as polyethelyne). To continue, this produces a
monolayer of tin on the glass that is ready or sensitized, to reduce silver
ions (Ag+) in the silvering solution. In this process the tin is oxidized to
Sn4+ and metallic silver (Ag0) begins to plate out on the tin layer.

The information, as applied for producing the silvered inside surface of a
glass dewar, states that the freshly silvered surface is rinsed with the
sensitizer solution followed by a distilled water rinse. This leaves a
surface layer of tin that does not allow oxygen in the air to form silver
oxide (Ag2O). The dewar is allowed to dry, is evacuated and heated etc.

If the silvered surface is to be copper plated or simply painted, then the
sensitizer rinse may not be needed.

It is interesting that the recipes I found for telescope making for
producing the silvered first surface do not mention the sensitizer rinse.
They are concerned about tarnishing, maybe this will help?

The recipe I have for the sensitizer is as follows:

Concentrate: 1 (one) gram stannous cloride in

10 (ten) ml distilled water.

Dilute concentrate for use as follows:

Dilute sol'n: 0.2 (one-fifth) ml concentrate in 1 (one) liter distilled

The dilute solution has a shelf life or not more than three hours.

The concentrate will last much longer but does slowly degrade forming "an
unappetetizing mess of yellowish solids"

The stannous chloride does not deteriorate in the dry state in the reagent

lester scovitch - -
E-mail address: scovitch-at-hotmail-dot-com