CT scanning

Natalie Scoullar <natalies [at] artgallery__wa__gov__au> writes

>I am exploring the idea of using a Computed Tomography scanner to
>examine a painting before treatment.  The painting is by Sir A.J.
>Munnings and it appears to have been painted over an old painting. I
>have been offered the use of a CT scanning machine by a local
>hospital radiology department.  Has anyone ever attempted CT
>scanning of a painting before?  Was it useful?  Are the exposure
>times and strengths to the X ray wavelengths used more damaging for
>an oil painting?

We recently had a small 17th century panel painting by Carel
Fabritius, the Goldfinch (1654), scanned by a CT. The scan was done
with a Siemens SOMATOM Sensation 16-slice, which is capable of
acquiring up to 32 slices per second and is the first system
commercially available that breaks the half-second rotation barrier
when operating at its maximum speed of 0.4 seconds for a full 360
deg. cycle.

See:
    <URL:http://www.medical.siemens.com/webapp/wcs/
        stores/servlet/PressReleaseView?storeId=10001&langId=-1
        &catalogId=-1&catTree=100005,13839,17705&pageId=21023>

See also:
    <URL:http://www.siemens.nl/persinfo/pressinfo.asp?id=798>

We already had a traditional x-ray of our panel, however, as the
background of the bird is a white wall, the lead-white obscured any
information about the panel itself. The result of the CT scan was
that we digitally were able to eliminate the paint layer from the
panel, thus obtaining a clearer view of what happens inside the
panel. By doing this we discovered at the right upper edge of the
panel an unexpected dowel hole. This indicated that Fabritius
re-used a part of a panel that originally would have been larger,
and where the current right edge at some time would have been a join
between two planks, assembled with dowels.

We had hoped also to be able to carry out dendrochronology by means
of the CT scan, however, this did not prove successful. Still trying
though.

It should be said, that the current 0.7-mm slice is not enough to
really determine or separate paint layers from one another. There I
believe you need a finer resolution. They exist but are not
commercially available.

I should be very pleased to exchange more information with you or
others about the use of this technique for 'two-dimensional' objects
like painting.

Jorgen Wadum
Chief Conservator
Royal Picture Gallery
Mauritshuis
PO Box 536
2501 CM
The Hague, The Netherlands
+31 70 302 3461
Fax: +31 70 365 3819


                                  ***
                  Conservation DistList Instance 17:66
                 Distributed: Thursday, April 15, 2004
                       Message Id: cdl-17-66-002
                                  ***