Soot on wall painting

Barbara Cerrina <nina [at] digicolor__net> writes:

>We need to clean a ceiling painted with tempera that is actually
>covered with a thick lay of soot.

You might be limited to dry cleaning methods to remove your soot. I
can give you a recipe for a cleaning putty we use in Denmark to
clean dirt off wall paintings that do not tolerate water.

Danish Cleaning Dough:

    700 ml water
    65 g (50 ml) copper sulphate
    20 g (40 ml) sodium carbonate
    780 - 850 g plain white flour (the putty is stickier with less
    flour)

    Preheat oven to 175 C (about 330 F). Place copper sulphate in a
    bowl. Boil the water and pour over the copper sulphate. Mix
    well. Add the sodium carbonate (this will cause it to bubble
    up). Mix well. Mix in flour. Turn out on flat surface and knead
    for about 5 min. If you have experience with making bread, this
    dough is stickier than bread dough. It is also blue. Form the
    dough into a loaf. Wrap it in a layer of wet cotton gauze. Wrap
    it again in a layer of aluminium foil. Repeat this two more
    times. This will keep the putty from drying out while baking.
    Place in oven. Bake for 90 min. Put it into a plastic bag
    immediately after it cools down. It is best when used fresh. If
    you do not use it within a few days, slice it up into pieces,
    wrap them individually and freeze them.

To use the putty, you pull off a hunk and roll it between your
fingers (make a snake), then roll it across the dirty surface. You
can also try dabbing gently. In cases where the dirt is really thick
we often vacuum the surface gently before we proceed with the
cleaning dough. That way it will not get clogged up with dirt
immediately.

For more robust paintings that can not tolerate water we use a
dry-cleaning sponge that works like an eraser produced by WISHAB. We
buy ours in Germany at Kremer Pigmente <kremer-pigmente [at] t-online__de>
Good luck,

Isabelle Brajer
Conservator
National Museum of Denmark
Conservation Department

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                  Conservation DistList Instance 12:46
                 Distributed: Monday, November 23, 1998
                       Message Id: cdl-12-46-006
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