Glass and Ceramics 183
Since human intervention has a high damage potential for ceramics, handling
and packaging of ceramics deserve special care. Recommendations for lifting
and moving objects as well as for the design of containers and transport
devices are available.
Cleaning of an object might be necessary to remove encrustations, developed
during exposure to soil, such as calcite, gypsum or silicates. Porous pottery
might be stained with iron compounds or deposits, resulting from the content
of vessels. Difficulties occur, when the “dirt” is soluble and has been carried
into the pores of the body.
“Repair” is considered as an early conservation intervention, forceramics
not only as precious artistic objects, but also as objects of daily use, such as
household ware. For the conservator today, early repairs might provide a
source of valuable information and might be kept to document the history of
the piece before burial. Other, more recent and aesthetically disturbing bond-
ing, filling or retouching materials might have to be removed, thus represent-
ing serious restoration problems. Removal of previous adhesives or coatings
is necessary if shrinking or yellowing of the polymer is affecting the artefact.
Mechanical tools, e.g.a scalpel, and a wide range of solvents are in use to
remove animal glues, bitumen, shellac, cellulose nitrates, silicones, polyvinyl-
acetates or epoxies from ceramics. Whereas the cleaning process might be suc-
cessful for surface coatings, the removal of organic polymers, formerly applied
as consolidants and thus penetrating the porous ceramic body, is hardly
feasible.
Due to the limited reversibility of consolidation treatments for ceramics,
new consolidations are carried out only if the object is seriously endangered,
e.g. when the ceramic body is crumbling or the surface decoration is flaking
off the surface. Materials, such as Paraloid B72 (already mentioned for glass
conservation) or silanes and siloxanes (used for stone conservation) can be
applied by brush, injection, spray or by immersion. Vacuum impregnation
might be useful to achieve deep penetration with the consolidant.
Fragile ceramics often need bonding of broken pieces. The choice of
the adhesive has to consider the general properties of a polymer, such as
durability and colour match, but also practical considerations, such as the vis-
cosity and the strength of the required bond. For fractured pieces with dis-
turbing gaps, filling with colour-matched polymers is quite common. Fillings
can be disguised even better by retouching, if ethically acceptable for the
object.
Conservation of ceramics, although dealing with relatively stable materials,
is a well-developed discipline. Advanced active and preventive conservation
strategies are applied to preserve the extensive collections of ceramics in muse-
ums all over the world, covering objects from several thousands of years of
ceramic production.