future proof file encryption

Mark H. Wood mwood at IUPUI.Edu
Mon Mar 2 15:19:13 CET 2009

On Fri, Feb 27, 2009 at 08:37:53PM -0500, Robert J. Hansen wrote:
> For long-term photographic storage, make a print from photographic film
> on archival-quality print stock.  Also, I'm given to understand that
> black and white photographs survive the aging process much better than
> color.

Silver chemistry is (or, at least, it used to be) much more resistant
to decay than color dyes.  You still have to be sure that the print
has been archivally processed (mainly to wash out all traces of hypo,
which otherwise will continue doing the job it has in the process and
eat away at the silver grains).  You still need to keep it away from
atmospheric contaminants when not in use.  You can plate the grains
using a bath of gold chloride to protect them a little longer.  You
can use vesicular film rather than silver, if you can still find it,
for even longer storage.  (Huh, *silver* chemistry is getting harder
to find.)

Used to be that color photos which had to be preserved for a long time
were stored as separation sets:  three silver images were made to
capture the three primary colors from the image, to be reassembled
later and reconstitute the color image using the ordinary dye
process.  Dunno if it's still done.  I'd put my trust in a
well-maintained redundant set of digital scans, these days.

Most photos won't really need all this fancy treatment; you enjoy 'em
while they last, and keep making new ones.  The problem is, often we
don't understand which ones *should* have special preservation, until
it's too late.

Mark H. Wood, Lead System Programmer   mwood at IUPUI.Edu
Mama don't take my Kodachrome away!
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