[rollei_list] Re: looks like ... agfa Sala

----- Original Message ----- 
From: "Carlos Manuel Freaza" <cmfreaza@xxxxxxxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx>
Sent: Monday, May 30, 2005 4:43 PM
Subject: [rollei_list] Re: looks like ... agfa Sala


> Thank you very much for the detailed explanation,
> Richard, it was necessary for me, in general we
> associate "film base" with the film back (acetate
> etc.) in Spanish.
> I am only using color films for 35 mm, however if
> nobody answers the question, I'll ask to a friend of
> mine tomorrow.-
>
> All the best
> Carlos

  Carlos, that is correct. The support or base is the 
material on which the light sensitive emulsion is coated. 
Many materials have been used historically, mostly either 
Cellulose Nitrate or some form of Cellulose Acetate. Many 
films are now coated on some form of polyester (Kodak Estar, 
DuPont Cronar, etc.). Polyester has the advantage of 
excellent dimensional stability, very high tear strength, 
and very low absorption of moisture during processing. 
However, it isn't perfect so Cellulose acetate continues to 
be used for many films.
   Cellulose Nitrate was the first flexible film base, 
introduced in the late 1880's. It has good mechanical 
properties and optical properties, but is very highly 
inflammable and is chemically unstable. Nitrate film was 
discontinued all together in 1951, at least in the U.S.  No 
16mm film was ever made on Nitrate, and Kodak discontinued 
it for still films in the early 1930's although Agfa and 
others continued to make it.
   Nitrate film evolves oxygen when it is ignited so its 
nearly impossible to extinguish. Nitrate film will burn 
under water and under sand!

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx


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