Re: [ARSCLIST] polyester or acetate? (complete)

[Mwcpc6@xxxxxxx]

I've found that the triacetate tape used by Kodak and perhaps some others  is 
much less translucent than regular acetate, especially the "long play" types. 
 It is hard to distinguish from "Estar" except in a side-by-side  comparison.
 
Film base was sometimes dyed to reduce halation effects so its transparency  
varies. 
 
However, in general, if light goes through the pack, it is acetate. Another  
test, to try on an inch or so of an end, is that if can be stretched,  it's 
polyester. Some of the tensilized polyester doesn't stretch much  though.
 
Mike Csontos
 
 
  
____________________________________
 From: ggkarman@xxxxxxxxxxxxxxx
Reply-to: ARSCLIST@xxxxxxx
To:  ARSCLIST@xxxxxxxxxxxxxxxx
Sent: 12/27/2007 8:56:29 P.M. Eastern Standard  Time
Subj: [ARSCLIST] polyester or acetate? (complete)


sorry, the previous post didnt get through correctly,  here the full version:

Dear list,

Due to a recent experience  with an historical sound archive, I am trying
to get some insight into the  details of aged magnetic tape and tape
preservation. I thought I had this  right but now I am confused by the
description the literature does relating  the methods that are used to
distinguish acetate from polyester tape. At  first I had understood that
acetate is tranlucent when held agains the  light, and here are some quotes
that support that:

"almost all post  WWII acetate tapes, you can hold them up to the light and
see light through  the edges of the tape  pack."
<http://www.richardhess.com/notes/formats/magnetic-media/magnetic-tapes/a-base
-film-primer/>

"All  standard play, most long play, and some double play acetate tapes
have a  translucent wind when held against a light source. This is not the
case  with PVC or polyester tapes." quoted from a technical paper found  at
<www.iasa-web.org>

however when I finally got to read what  seems one of the most quoted
studies on the topic (IPI Storage Guide for  Acetate Film, p 21) I found:

"When viewed "edge on" (holding the reel  up to a light source and looking
through the spokes of the reel), polyester  film will transmit much more
light than acetate or nitrate (see fig. 20).  some light will pipe through
the edges of the film with acetate, but  polyester will look much
brighter."

and fig. 20 shows 2 tapes, and  the footnote says:

"When held up to a light source the polyester film  "pipes" the light
throught the edge of the film, while acetate and nitrate  do not.
(polyester film shown at right)"

and the tape of the right  indeed lets more light through!

In my archive I found both translucent  and opaque tapes but now I am
confused.... any comments?

Thank you  for your help

Gregorio  Karman





**************************************See AOL's top rated recipes 
(http://food.aol.com/top-rated-recipes?NCID=aoltop00030000000004)