Non-aqueous consolidants for matte, flaking paintings

Bettina Ebert <ebertbettina [at] yahoo__co__uk> writes

>I am currently treating two paintings on canvas which have a very
>matte surface appearance and exhibit extensive tenting paint, with
>associated flaking. There is almost no internal cohesion, and the
>paint layers are very brittle. Plasticising the paint with solvent
>vapours has had only minimal effect. I had to rule out aqueous
>treatments due to large amounts of water-soluble components in the
>paint layers. I have tested numerous consolidants with added matting
>agents, but have not had any success so far. ...

Maybe the following materials might be of help: You could try to use
Klucel G (Hydroxypropylcellulose)which can be dissolved in
2-propanol. It is possible to add a non-polar solvent like benzine
(3 parts 2-propanol/1 part benzene).

This material may re-establish the internal cohesion of the paint
layer. I doubt that it will work in treating tented paint layers.

You could also try to use Plexisol P-550/Lascaux P-550-40TB-Acrylic
resin. It has a 40% solid content of butylmethacrylate in benzene
100/140 and is also soluble in White spirits, VM&P Naphtha, Xylene,
Toluene and Acetone.

Obviously you would want to avoid Toluene and Xylene.

I would dilute the 40% solution to a 5% and a 10% solution and start
with the 5% P550. Apply some of the solution on a small test area
and let the solvent evaporate over night. The next day you need to
heat up the paint area were you applied the P-550 to 55 deg. C (warm
sandbags, warm air, heating pads, heating spatula etc., maybe in a
combination of heating the reverse part of the painting and the
paint layer)in order for the P-550 to heat set. If you use heated
sand bags and/or heating spatulas on the paint layer you need to
have a layer of thin silicone paper between the paint layer and the
heat source as it will stick to the unprotected paint layer.

Maybe 1 treatment will not be enough and you may have to repeat the
procedure.

The P-550 will/may leave a shiny surface depending on how much of
the material went into the paint layer and how much remained on top
of the paint layer which is, of course, also dependant on the % of
the solution. You may want to start with an even weaker solution of
2-3% of P-550.

I have had good success in removing excess P-550 from matte surfaces
with the benzene 100/140 or Acetone, I used P-550 on medieval
azurite or occasionally on contemporary matte paint layers as a
*last resort* if other materials like the above mentioned Klucel
G/Klucel M or Jun Funori for example, to name only 2 materials
wouldn't work.

You didn't mention which materials you tried, just that the paint
layer is extremely water sensitive. I would hope that my suggestion
will work for you and appreciate some feedback.

    **** Moderator's comments: Bettina wrote back with the following
    additional comments

I forgot to mention another treatment possibility for the 2
materials I recommended in my first mail:

You could try to use the Klucel G to treat the internal cohesion of
the paint layer and then apply a 3% or 5% solution of the P-550 from
the reverse of the painting to consolidate the flaking.

You would have to apply the P-550 in a small test area from behind
and watch the painting's front at the same time until you actually
can see the P-550 seeping through the canvas to the front and appear
as a shiny substance in the paint layers cracks, provided that the
paint layer has cracks.

You would then also have the solvents evaporate and try to
consolidate the flaking paint layers the next day. Ideally there
should be a layer of adhesive right underneath the paint layer. If
you would be able to soften the paint layer with solvent vapors,
humidity and/or heat you may be able to consolidate the paint layer
as described before. With this procedure you would not need to
remove excess P-550 from the paint layers surface or only to a much
lesser degree.

Of course it depends to a large degree on the permeability of the
canvas and the ground layer if this kind of treatment will be
possible and you may have to try with different percentages of the P
550 to achieve that the material permeates through canvas and ground
layer in just the right way to build a layer of consolidant beneath
the paint layer.

If you should have excess P-550 on the canvas reverse you can try to
extract it with the solvents mentioned in my first email.

Bettina Landgrebe, conservator
The Chinati Foundation
PO Box 1135
Marfa, TX 79843
432-729-4742
Fax: 432-729-4597


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                  Conservation DistList Instance 21:54
                  Distributed: Friday, April 11, 2008
                       Message Id: cdl-21-54-001
                                  ***