Dry point

Caroline O'Rorke <icsbris<-a t->ibm< . >net>

Caroline O'Rorke <icsbris<-a t->ibm< . >net> writes:

>The paper colour in the plate area is off white and has the
>appearance of course sandpaper. There is a white crystalline deposit
>over all the area (tests show sodium . ...The heavily inked area
>(shadow area of the face)  shows that the ink is lifting off the
>surface. The definition of line has been lost and shows deposits of
>white powder.... My preliminary research has lead me to believe that
>the print was treated with sodium borohydride. ...I am interested in
>hearing from people who have sighted similar problems and would like
>to hear of any ideas on possible stabilisation treatments.

I have had similar problems with white crystal deposits in the past,
they appeared on prints after various treatments:

    1.  after washing a poster (20th c.) white crystals appeared
        from an unknown source could be the inks or salts in the
        water.

    2.  15 years ago bleaching with calcium hypochlorite was
        recommended and if the bleaching solution  wasn't well
        filtered white deposits of the insoluble calcium crystals
        remained on the print after it dried.

    3.  if the deacidification was done with the aid of a calcium
        hydroxide solution that wasn't well filtered  white crystals
        would appear on the surface of the paper after drying.

The solution for #1 was washing it on a vacuum table with ethanol
which removed the crystals. The solutions for #'s 2 and 3 is washing
the paper in an acidic solution (acetic acid 2%). It is highly
recommended to deacidify the paper after this treatment with
magnesium bicarbonate.

Since the author states that the crystals on the paper are sodium
crystals it is possible that there was an attempt to bleach the
print with sodium hypochlorite that wasn't rinsed well after the
treatment, therefore , I would recommend using sodium thiosulfate
(antichlor 2-3%).

I find it hard to believe that there was an attempt to bleach the
print with sodium borohydride since sodium borohydride in a watery
solution is extremely soluble and crystallization of such a solution
after drying is rare. But if the case proved to be borohydride
simple washing should be enough to eliminate the crystals.

Michael Maggen
Senior paper conservator
The Israel Museum
Jerusalem, Israel

                                  ***
                  Conservation DistList Instance 11:20
                 Distributed: Thursday, August 28, 1997
                       Message Id: cdl-11-20-001
                                  ***