The use of canned air is just fine, however, it can push large [hard and
relatively massive] dust particles across the surface of the film and
sometimes cause "very minor" scratching.

Using a brush will do the same, only you are sure very fine small scratches
will result as you remove any loose dirt or dust using mechanical action.
The brush will not remove the very fine dust stuck to the gelatin following
the "swelling & de-swelling" process outlined below.

The issue with canned air is the propellant in the can.  If used at the
wrong angle, propellant from the can will spew from the probe tube and
deposit on the film.  If the "ice" [CO2, white solid] is directly on the
gelatin side, and is there for more than just a brief moment, the cool
propellant will attract water from the air, and then slightly and
momentarily, swell the gelatin.  When the swelling goes away, the "swelling
and de-swelling process" can, and I mean 'only' can, permanently trap small
dust particles that were formerly just firmly sitting on the surface [read
old very-fine dust] to the gelatin.  If for some reason you should spew ice
all over the gelatin side of the film, you can be sure this "fault" will
happen.

If there is a lot of white stuff [CO2 ice] on the "film base" side, the cold
will attract humidity/water to the gelatin on the other side of the film and
this fault may occur.

This fault is not as true of dust on the film base side.  The base side is
the shiny side; there are exceptions.  Cellulose acetate (and cellulose
nitrate) don't swell much when exposed to water or humidity.  All 35-mm
format slides are on cellulose acetate base, even today.  The film base
certainly doesn't respond as fast as gelatin to water and humidity, which
responds almost instantaneously.

Film tends to curl away from the gelatin side, because gelatin swells in
water/humidity and alcohols & their vapor.

I dust with canned air, at the correct angle; this can be determined by
mocking up the process first.  Slides are difficult because they have the
cardboard or plastic holder.  If I'm going to scan the slide, I will remove
the housing and leave it off, unless the client insists.  Then I will
re-attach a new plastic snap-on (easy to remove again) mount.

If dusting with air doesn't work, I go to a brush that has not been around
face oil, around hands that have face oil on them, or the like.  I keep this
special antistatic brush in it's little plastic box, when not in use.
[NOTE: I have seen folks whisk this brush across their cheek, before using
it each time, to get a little face oil on the tips to help attract the dust
from the surface of the film.  Yikes!!]

If this fails as well, I use an aliphatic solvent such as: n-Hexane,
n-Heptane, Odorless thinner, White Spirits, petroleum Benzine or Stoddard's
solvent.  I may or may not use mechanical action with the solvent.  A simple
dip and dry with canned air, when held by the edge, is the first option.
Using a lint-less cloth such as a Pec*Pad is the next step; micro-scratching
will surely result from the rubbing.  I have also used hand-rolled cotton
swabs, but you can be sure to cause scratches; these new micro-scratches
will have to be less harmful to the image than the "stuff" I was trying to
remove.

Mounting the naked film (out of its holder) in Stoddard's solvent on a
high-resolution Epson flatbed scanner is the way I scan slides; this is
messy and slow.  It is called "wet mount" scanning, but has nothing to do
with water, the wet is Stoddard's solvent.  The results are fantastic, as
good as possible, except when using a new drum scanner at 5000-8000 ppi, and
only on new film that is not brittle or mechanically damaged from base
deterioration.

I DO NOT [ever, ever] use any proprietary film cleaner, or,
alcohol-containing cleaner, alcohol-based cleaner or straight alcohol [right
from a new bottle, from the scientific supply house] of any type including
methanol, ethanol, propanol, butanol, mixture of the latter or any other
solvent that will swell gelatin [exotic solvent with a several -OH groups on
them].


Tim Vitale

Paper & Photography Conservation
Oriental Scrolls & Screens in the Western Manner
Digital Facsimiles & Digital Restoration
Remastering still Film to Digital [distorted film too]
Archive & Collection Surveys
Video & Film Preservation Surveys
Preservation & Imaging Consulting

Vitale Art Conservation
2407 Telegraph Avenue #312
Oakland, CA 94612

510-594-8277
510-508-4162 cell
510-891-1602 fax
[log in to unmask]

Website: http://vitaleartconservation.com/
Resume: http://vitaleartconservation.com/vitale_long-resume_v21.pdf
Video Preservation: http://videopreservation.conservation-us.org/ (2007)
Albumen Photography website: http://albumen.conservation-us.org/ (2001)
Brief History of Imaging Tech: http://vitaleartconservation.com/bhit.pdf





-----Original Message-----
From: Museum discussion list [mailto:[log in to unmask]]On Behalf
Of James Tichgelaar
Sent: Wednesday, June 13, 2012 12:40 PM
To: [log in to unmask]
Subject: Re: [MUSEUM-L] Cleaning slides


Compressed air of any kind can just lodge particles deeper into the soft
emulsion.  I use an anti-static brush designed for film available through
the few remaining photo suppliers (try Freestyle Photographic).

From: Museum discussion list [mailto:[log in to unmask]] On Behalf
Of Pamela Endzweig
Sent: Wednesday, June 13, 2012 3:33 PM
To: [log in to unmask]
Subject: [MUSEUM-L] Cleaning slides

Hello colleagues --

We are currently scanning a batch of 35 mm slides and have found some to be
a bit dusty.  I recall encountering cautions re propellants in cans of
compressed air, but I can't put my finger on where I read that.  So: what is
current wisdom on cleaning slides -- hurricane blower alone? And then deal
with dust electronically as needed for enlargement, publication, etc.?  Or
is there a "safe" kind of commercially available compressed air?

Many thanks in advance!

Pam



--
Pamela E. Endzweig, Ph.D., RPA
Director of Collections & Senior Research Associate
Museum of Natural and Cultural History & State Museum of Anthropology
1224 University of Oregon / Eugene, OR 97403-1224
Ph 541-346-5120 / Fax 541-346-5334




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