RE: [AV Media Matters] acetate tape and plasticizer crystals

[Mick_Newnham@screensound.gov.au]

>From a FILM perspective (I have NOT tried this on audio/mag
materials), the
crystalline plasticiser (tri phenyl phosphate, or TPP for film) deposits
can be removed with a mixture of ethanol and some other "safe" solvent
("safe" for the film and person).  I have used 3M's HFE-7100 with
about 2 -
5% v/v ethanol ("absolute" not 95% or other denatured form.
Concerns about
the water content).  The reason for dilution is that ethanol is a
very good
solvent for the plasticisers.  Too good in fact, and will rip out the
plasticiser that still remains in the base unless great care is
taken.   3M
also market HFE-71DE which has a small quantity of ethanol in it and seems
to work well for this purpose but perhaps not quite as well as the diluted
EtOH/ 7100.  Even using this approach the object should not be saturated
but just lightly swabbed.

Maybe this solution is OK for mag, I'd be interested in others perspective
on the suitability, or results.  Especially if the deposit is not the base
plasticiser but a binder lubricant.

Secondly, if the base has begun to decompose (a reaction initially
co-dependent upon water) is it a fair assumption the binder also
hydrolysing?  How rapidly does the binder change in viscosity/Tg?  Has
anyone looked at changes in the morphology or mobility of the oxide in the
binder of decomposing mag materials and the effect this might have on the
signal?  (Sorry for hijacking the topic but I am researching any similar
events in silver/gelatin photography and am just curious)

Mick Newnham
Engineering and Research Group
Preservation and Technical Services
ScreenSound Australia