[filmscanners] re: Cleaning old Kodachrome slides

["HPA" <tom@historicphotoarchive.com>]

I do a substantial amount of scanning vintage Kodachrome, as well as
Anscochrome, tri-shot, paget, findlay color, Autochrome and all the other
early color materials.

I would recommend this workflow, which is my personal "default setting".
First, use a light table and organize all the slides in the order they were
shot in.  You can use the mount markings, differences in the number stamp
impressions, subject matter, etc. to sort the slides back into original
camera order.  Put them in pages in chronological order and throw nothing
away, the reason i will explain.

select the slides for scanning, and carefully remove the film from the old
mount.  Do not discard the mount.  (After scanning, put the slide into a
Gepe mount and store with the original mount).  When you have the film out,
check the edge.  The kodak date codes appear about every sixth frame.  If
you need to get a date on the image, look at the adjacent slides and pull
the film until you find the date code.  It is a series of two characters,
circles, squares, triangles, etc. these date the film.  Your pictures were
likely taken within half a year, up to a year later.

Kodachrome had a varnish on the surface until about the mid 1950s.  You will
want to remove this varnish, which is known to promote mold growths.  The
emulsion of early Kodachromes is much softer than modern ones, so use the
greatest of care.  I use lens tissue and Edwall film cleaner to remove the
varnish.  Of course the dirt comes off at the same time.  Be very light and
never use the same area of a tissue again, because the contaminants that
were removed will scratch the film on the second swipe.  It really helps to
have a diaphram air compressor, set to 40 lbs pressure.

Use the film holder to scan the image.  I would suggest that you have at
least two programs for scanning, perhaps Silverfast and Vuescan.  They are
so different that you will want to select the program on a case by case
basis.  Strange lighting situations are, in my humble experience, more
faithfully reproduced by Silverfast.  Vuescan has much better focus control
and slightly better shadow detail.  I use both all the time.  Each program
has its own frustrating limitations, and if you can't get where you need to
go, try the other.

If you have warped film, try placing an anti-newton ring glass on top
(only).  I get the glass from german slide mounts.

If the base side of the slide has physical damage, such as serious water
damage or heavy scratches, you need to use an extremely fine grit abrasive
such as red jewelers gold polish brick, and dissolve it it film cleaner and
use a tissue to remove the top layer of the emulsion side, going below the
defect.

Be sure the film is regular kodachrome.  Other types of film require
different strategies.  Kodachrome before January 1939 is very unstable and I
would suggest trying any treatment on a less important example from the roll
before proceeding.

In the prosumer class of scanners, diffuse light source ones work better for
Kodachrome IMHO.  It is very difficult to get all the detail off old
Kodachromes.  be sure to turn off all automatic dust removal features.
Automatic level and color correction can give you a good idea of what the
slide can be made to look like, but these programs will likely lead to
clipping, so it is better to set your levels and corrections manually using
a historgram.

Do not use PEC on French Kodak film shot before 1946.

best of luck

Tom Robinson

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