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Re: Paper deacidification

At 02:47 PM 09/29/2000 +1000, you wrote:
>From discussions which occasionally come through on the List, we note
>that many conservators use calcium carbonate as a deacidifier of paper
>materials.  Others use calcium hydroxide.  Still others use magnesium

There was some discussion on the comparative merits of deacidification
methods on the List about two years ago, mainly Bookkeepers vs Wei T'o. I'm
sure there is still disagreement among conservators about which chemicals
are safest and most effective. Some are concerned about the longevity of
the calcium buffer. Since there have probably been recent developments, it
might be worthwhile to reopen the discussion.

I have used Bookkeeper spray, which leaves a calcium buffer, but found it
to be too expensive to use to deacidify the pages of a 400-page, 8 1/2 x 11
book. Coverage of one canister, at approximately $40/per, is about 25 pages
of that size.

This spray is now sold under the the name "Archival Mist." Preservation
Technologies uses the Bookkeeper process (magnesium oxide)in mass treatment
of books and materials in their plant in Pennsylvania. The company has
contracts to treat collections for the Library of Congress and many
university libraries. They will also treat individual books, bound or
unbound, far cheaper than using the spray yourself.

 Preservation Technologies may be reached by calling 800-416-2665 or at
their website:


I also used Magnesium Bicarbonate water to deacidify a collection of
roto-sized newspapers. The recipes (from Curatorial Care of Works of Art on
Paper, Anne F. Clapp) are easily made at home.

"1. Made with proprietary soda water:

        1 bottle of soda water (Canadian Club)  300 ml. or 10 1/2 fl.oz.
        Powdered Magnesium Carbonate            6 gm. or 9 teaspoons

Put the magnesium carbonate in an empty bottle of slightly greater capacity
than the soda water bottle and one with a tightly fitting cap or cork.
Place both bottles in a refrigerator overnight or until thoroughly chilled.
The reason for keeping the materials cold is to increase the quantity of
the magnesium carbonate that will go into solution. As quickly as the
operation can be done, open the soda water bottle and pour the charged
water into the magnesium carbonate bottle. Cap firmly and agitate gently
for a short period. Return to the refrigerator. Keep the magnesium
carbonate from settling for the next half hour by repeating the periods of
gentle agitation and return to the refrigerator. Allow the excess magnesium
to settle for several hours or overnight. Siphon off the clear liquid. Keep
firmly capped and cool.

2. Made with a soda water siphon:

The most convenient way to make magnesium bicarbonate water is with a
standard, strong walled, soda water siphon. It must be modified by cutting
a generous inch off the siphon tube so that its end will be clear of the
sediment of undissolved magnesium carbonate.

        Distilled water or de-ionized water     300 ml or 10 1/2 fl.oz.
        Powdered Magnesium Carbonate            6 gms or 9 teaspoons

Put all ingredients and the siphon bottle in the refrigerator until they
are thoroughly chilled. As quickly as possible so that the temperatures
will remain low, mix the water and magnesium carbonate, and funnel the
mixture into the siphon bottle. Discharge the carbon dioxide cartridge.
Return to the refrigerator and allow the undissolved magnesium to settle
for a number of hours or overnight. Siphon off the clear liquid. Keep
firmly capped and cool."

Please understand that I am merely giving information about these methods
of deacidification, not recommending one over others.

Sorry for the long post; in responding, please do not repeat the entire

Betty Storz   storz@mcn.org
Mendocino, CA

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