Removing cement from ceramic panels

Naoko Fukumaru <naokofukumaru [at] yahoo__com> writes

>We de-installed 19th century Persian wall fountain ceramic panels
>(four panels, each about 67 x 52 x 5 cm) from Islamic Gallery at The
>Detroit Institute of Art. We discovered that the cement (5 cm
>thickness and over 100 kg with two panels) with a metal mesh
>reinforcement has been previously applied to the backside of the
>panels during the de-installation.
> ...
>I have begun to remove the cement from the back side of the panels
>using chisels, a hammer and a hacksaw. I found that the ceramic body
>is very soft and porous while the cement is very hard and dense. I
>am concerned about giving the vibration to the object, even thought
>the object is padding with polyethylene forms to absorb some
>vibration. Also this method is time consuming and physical work. Of
>course, I do not mind that if this is the safest way for the object.

We have a 4 year project nearing completion which includes removing
cement from internationally important Bronze Age ceramic vessels. It
is very slow work and, as you have discovered, technically
challenging.  The team here mainly use power tools to remove the
bulk of the cement.  The power tools include hand drills, pendant
drills and Dremel style drills and vibrotools. By using high
revolution tools you can also use diamond edged cutting wheels and
bits.  These are the most practical drill bits we have found as they
do penetrate the cement relatively easily.

The use of power tools does require a certain amount of practice to
build up your confidence when working with them on an artefact. Also
you need to be aware that working with continual vibration through
your hands can cause the circulatory disease called Vibration White
Finger, we have implemented strict health and safety rules about the
amount of time anyone can spend using the tools mentioned earlier.

The team try to cut down the amount of vibration in the way you
have, ie plenty of packing, however you will probably find there is
a maximum amount of packing you can use as the vibration from the
tools can cause the object to bounce away from the tools as they cut
into the cement in excessive packing.

The project here has been very successful and we have had virtually
no losses to the original very soft ceramic vessels.  The vessels
conserved in the project all come from the county of Wiltshire and
include vessels from the World Heritage Sites of Stonehenge and
Avebury.

Louisa Burden
County Conservation and Museums Manager
Department for Children, Education and Libraries
Wiltshire County Council
+44 1722 331321 or +44 1225 713738
Fax: +44 1722 415017 or +44 1225 713993


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                  Conservation DistList Instance 17:38
                 Distributed: Tuesday, October 28, 2003
                       Message Id: cdl-17-38-003
                                  ***