Roman wall paintings

Karin Abelskamp <k.abelskamp [at] archeologie__nl> writes

>... The fragments are being cleaned
>carefully by three university students with water, dentist
>instruments, soft brushes and cotton swabs. ...
>...
>Advised by a conservator from Maastricht, we used a water soluble
>acrylic dispersion, Primal, on site on some of the most brittle
>fragments (20%). We would want to use it for consolidation, too
>(10%) either by spraying or by submerging the fragments. ...

Primal WS24 works extremely well as a consolidant for many damp
archaeological finds. One advantage is that objects can have
repeated applications without the previously applied Primal
redissolving. When it is completely dry it is also compatible with
solvent based solutions of acrylic copolymer resin (e.g Paraloid
B72) as an adhesive or for further consolidation. Both Primal WS24
and Paraloid B72 are remarkably stable. See the article on
consolidation of archaeological bone by S. Koob in the IIC
conference proceedings, Adhesives and Consolidants, Paris, 1984

If the fragments were damp when found (as would be expected, given
the site) we would recommend continuing with the use of Primal WS24,
applied by allowing it to be absorbed into the body of the fragment
via a pipette, with repeated applications. The fragments can be
allowed to dry out slowly (with careful monitoring to watch for
dimensional changes or the emergence of salts) and applications of
Primal WS24 repeated until sufficient strength is obtained. Please
remember that an object is at its weakest when just consolidated--it
has all the extra weight of the consolidant solution, the
lubricating action of the consolidant and no strength yet from the
consolidant--and should not be moved. We place fragments on trays on
silicone release paper or Teflon coated cloth during consolidation
and allow them to remain unmoved until the process is complete.
After complete drying, any excess consolidant can be removed by the
very light application of a cotton wool swab dipped in acetone.

Under no circumstances could we recommend the use of white wood glue
(generally a PVA formulation). PVA tends to form a thick layer of
consolidant close to the surface which prevents the migration of
moisture and salts, leading to the enhanced crystallisation of salts
just below the surface. The decorated surface then blisters and
spalls off.

Congratulations on getting to work on the fragments so quickly. Many
excavations allow the wallpainting fragments to dry out completely,
making it extremely difficult to remove the mud from the surface.
Hope this helps,

Richard and Helena Jaeschke
Archaeological conservators


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                  Conservation DistList Instance 16:24
               Distributed: Thursday, September 26, 2002
                       Message Id: cdl-16-24-001
                                  ***