Deacidification sprays and blueprints

In the Archives list, on Thu, 14 Sep 1995, Sandy Hempe wrote:

> The discussion on blueprints and alkaline conditions made me wonder how
> most people deal with the problem of housing blueprints.  I also have
> been housing blueprints in non-alkaline conditions, because I had read
> and heard about the fact that they don't react well to an alkaline
> environment.  However, in the session at the SAA conference titled
> "Washington Design: Landscape and Architectural Records of the Nation's
> Capitol", Michele Hamill from the Library of Congress said that they
> routinely insert a buffered sheet of paper in all encapsulates, including
> blueprints.  She said that they had decided that the beneficial effects
> of the buffering to the paper outweighed the possible adverse effects to
> the color of the blueprint.  This makes sense to me.  I'd like to hear
> what others think about this.
>
> Sandy Hempe
> Conservation Technician
> Missouri State Archives
>

I have cross-posted this posting to Conservation Distribution List
in the hope that someone more knowledgeable than I am will expand on
(or correct) what I say.

It may be that the Library of Congress has decided, on the basis of
their own research and "clinical" observations, that the advantages
of encapsulating a sheet of buffered paper with an untreated,
potentially or already acidic, blueprint outweigh the likelihood of
accelerated damage caused by the encapsulation (reported by LC's own
researchers some years ago).  It *is* apparently the case that the
imaging chemistry of blueprints is incompatible with a buffered
environment. Blueprints should never be washed in alkaline baths or
non-aqueously "de-acidified," lest they change or lose color.

The relatively gentle "buffering" provided by a sheet of pH 8.5
paper in contact with the reverse of a blueprint *may* not be
sufficient to alkalize the environment within a capsule or folder
significantly--that is, it may not be alkaline enough to react with
the image chemistry of the blueprint, even though it can reduce the
hydrolysis rate within the capsule or the adjacent paper.  I
wouldn't want to adopt this strategy wholesale for blueprint
storage, and I'm sure LC has not.

Remember that there is apparently a particularly aggressive
environment inside a capsule accelerating hydrolysis (presumably)
and consequent damage to the encapsulated cellulose.  That may not
be the case inside an ordinary buffered enclosure--the alkalinity in
the complex in that case *might be* sufficient to produce a reaction
with sensitive media.  All of this will probably be dependent on the
severity of the storage environment.

Could someone who can describe the reactions going on here, and
project to the consequences of mildly alkaline environments for
blueprints, answer this question for the archives list (and me)?
This reminds me of the controversy over buffered or neutral
enclosures for albumen prints in the last few years, where I believe
photo conservators have recanted the insistence on neutral housing,
at least in appropriate environments.

Karen Motylewski
Directory, Preservation and Conservation Studies
Graduate School of Library and Information Science
University of Texas at Austin
Austin, TX 78712-1276
512-471-8291
Fax: 512-471-8285

                                  ***
                  Conservation DistList Instance 9:27
                Distributed: Tuesday, September 19, 1995
                        Message Id: cdl-9-27-003
                                  ***