[pure-silver] Re: Tech Pan officially discontinued, substitu
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Thu, 16 Sep 2004 22:07:30 -0700
----- Original Message -----
From: "Michael Briggs" <MichaelBriggs@xxxxxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Thursday, September 16, 2004 7:05 PM
Subject: [pure-silver] Re: Tech Pan officially discontinued,
substitu
>
> The exact words at the Kodak link provided by Claudio are
> "... we no longer
> manufacture the ESTAR support on which the 35 mm product
> was coated.". Kodak
> makes or buys ESTAR in several variations: the old
> datasheet (P-255) for Tech
> Pan lists the base as ESTAR-AH for 35 mm, ESTAR Thick for
> sheets. (120 is on
> 3.6 mil acetate.) Since Kodak specifically mentions that
> the base is
> unavailable for 35 mm Tech Pan, I assume that they no
> longer make ESTAR-AH.
> AFAIK, all Kodak sheet films are on a thicker ESTAR base.
> If Kodak were giving
> up completely on ESTAR they would probably have to
> discontinue all sheet film.
> As to the impact on other products, I suggest hunting down
> the datasheets and
> seeing the exact words used for the base. Anything on
> ESTAR-AH may be in
> danger.
>
> As Richard said in his email, ESTAR is a tradename for
> polyestar. Polyestar is
> more dimensionally and chemically stable and more tear
> resistant than acetate
> base. It is not commonly used for roll film.
>
> Polyestar film base is a spin off of the Cold War -- it
> was developed by Kodak
> for the CORONA spy satellites because film on acetate base
> was ripping in the
> camera. A quick google search found
> http://www.globalsecurity.org/space/systems/kh-1.htm
>
> --Michael
>
I can't find the mention of Estar on the above site.
Estar is a polyester film very similar to Dupont's Mylar and
Cronar, all three are chemically related to Dacron and were
developed from it. Mylar dates from the early 1950's. I am
not sure when polyester was first used for film base but it
must have been around this time. Polyester has the advantage
of good mechanical properties, it is strong and does not
tear easily. It also very dimensionally stable which is
important in applications like aerial mapping, motion
picture photography, and color separation work. Polyester
base is also free of solvents so it doesn't age in the same
way as cellulose acetate types or cellulose nitrate. Its
shortcoming is that it cant be slplced using a solvent. It
must be taped or by means of heat splicers. Polyester also
has very good optical properties, it is very transparent and
is homogenious. The lack of solvent also means that the
mechanical characteristics of the support change little with
age and that there is nothing in them which can evaporate to
attack the image of either B&W (silver) or dye based films.
The AH in Estar AH means Anti-Halation and probably
refers to either a back coating or to a pigment included in
the support. The pigment is common in 35mm black and white
negative films but is not used in color films, either
negative or positive. These rely on an anti-halation layer
under the emulsion which also serves to eliminate light
conducted through the length of the film.
Again, my surmise is that Kodak has decided that it is
more economical to buy their film base from some outside
source than make it themselves. I doubt if the
discontinuance of Technical Pan has anything to do with the
support since it is used in a large variety of other Kodak
products including much motion picture film. Dupont still
makes Cronar and Mylar but it is now licensed to a factory
in China. If China ever adopts modern environmental
protection standards it will be interesting to see how many
products made there for the U.S. and European market come
back home.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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