Air abrasion using baking soda

In Conservation DistList Instance: 18:51 Tuesday, April 26, 2005
Gordon A. Lewis <gal [at] art-conservation__org>

>I recently saw a demonstration of baking soda as an abrasive to
>remove many different accretions; it seemed interesting. The
>demonstrators told me it is in use in dentistry and other arenas.
>According to their literature, baking soda has a MOHS of 2.5 and can
>be used in dry or wet applications. Has anyone used it; have any
>experience; knowledge?

At the British Museum we have often used baking soda as an
airbrasive powder to clean stone objects.  The advantage of it is
that is soft and with care will not abrade stone.  A few years ago
we airbraded a red sandstone Ogham stone with baking soda.  It is
riven with cracks at oblique angles to the surface, which present
delicate feathered edges of stone that would be highly vulnerable to
more aggressive abrasives such as silicon carbide.  The stone was
blackened by a heavy carbonated surface incrustation and impossible
to clean by any other method.  We were able to take off the
incrustation without damage to the stone and today it is to be seen
on exhibition in the Great Court.

There is a safety hazard though.  This large scale operation puts
large quantities of fine particles in the air and you would need an
air-fed mask and protective clothing.

Eric Miller
Conservation
British Museum
+44 20 7323 8428


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                  Conservation DistList Instance 19:4
                  Distributed: Wednesday, July 6, 2005
                        Message Id: cdl-19-4-009
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