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Subject: Diazo microfilm

Diazo microfilm

From: Charles Stewart <cstewart>
Date: Monday, February 27, 1995
It's always been my understanding that diazo materials are not
considered archival, in the same sense that correctly processed and
stored silver gelatin films are.  Image Permanence Institute may be a
good resource for information on the subject.

It is well to bear in mind, though, that diazo films are duplicates
(copies) and in the case of loss of such a film, a replacement can, in
theory, always be made by creating a new duplicate from the master
negative or silver "printing master."  This replacement may be either
another diazo negative or a silver positive.

As to whether or not these materials "self-destruct,"  I suppose it
could be said that they do so, mainly because the image is composed of
dyes which are bound, eventually, to shift and fade.  The action of
light is a catalyst for this type of deterioration and it stands to
reason that service copies will be exposed to intense light (in the
reading/printing machines), especially the more popular items.  We've
had diazo films submitted for duplication here which are no longer
legible due to fading.

ANSI/AIIM has a publication on standards for diazo films which briefly
treats the issues of lifespan and archivability.  Somebody else may know
of something more thorough.  I don't have the thing at hand but, as I
recall, this publication claims long-term storage potential (up to 100
years, I think), providing dark storage is observed.

Diazo production uses aqueous ammonia to destroy the stabilizer
incorporated in the material, in turn enabling the dyes to couple with
the diazonium salts.  This use of ammonia concerns me, from a
preservation standpoint, as much as the actual lifespan of the diazo.
Freshly-made diazo may "outgas" ammonia, which is said to be a pretty
potent oxidant. I wouldn't want ammonia vapor around my silver films,
for this reason.  I don't bring this up to incite panic; many
institutions keep service copies of both types (silver and diazo)
without any special concern. Moreover, I have noted a trend to regard
"use" copies as more-or-less expendable.  Since latter-day preservation
filming projects usually require a second silver negative (duplicate
"printing master"), it's felt, apparently, that replacement of lost,
damaged or deteriorated use copies is a comparatively simple matter and,
from an operational standpoint, this is so.

There are recently-published guidelines (Research Libraries Group,
PRESERVATION MICROFILMING HANDBOOK, 1992) which allow generation of
diazo service copies, so in this sense you may regard the practice as

We produce only silver service copies here.  My visits to microfilm
vendors in this region suggest that the air in lab areas where diazo is
made can be quite heavy with ammonia fumes.  Worker safety aside, it
might be interesting to sound out Image Permanence Institute on the
possible effects of ammonia vapors on raw and processed silver films.

My advice, for what little it may be worth, would be to switch to silver
gelatin positives, if your institution can afford the additional
expense.  Your investigations and other contributions to this forum may
compel you to decide otherwise, in which case I may also be glad to
stand corrected in the matter.  Good luck.

Chas. Stewart
Sr. photographic technician
Library Photo Service
U.C., Berkeley

                  Conservation DistList Instance 8:69
                Distributed: Tuesday, February 28, 1995
                        Message Id: cdl-8-69-006
Received on Monday, 27 February, 1995

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