X-ray machine

We are in the market for a high quality "soft"x-ray machine to carry
out radiography of easel paintings on both wood and canvas supports.
I have used industrial as well as medical machines, mostly
professionally adapted by qualified x-ray technical people, but I'm
still not getting what I want in contrast.  I have long wanted a
Gilardoni "Art-Gil" unit which goes from 5-80 kv, but these are no
longer in production and were also quite expensive (about US$32,500
in Australia).  In recently speaking with sales reps of x-ray
equipment, I have been cautioned that new technology has made low kV
radiography much higher quality because the power supplies are much
more stable enabling the tube to maintain a steady kV over an
exposure of 1 minute or so- but I don't know if this is marketing
hype or of real concern.

I am looking for a portable unit with a control box which operates
off of single phase 220-240 volt a.c., which has a head on a 5 meter
lead which can then be put in a lead-lined box to shoot up through
the painting into film which is sealed in black polyethylene bags
and covered with lead impregnated rubber.  Typical exposures will be
around 1 minute at 20 kV at 5 mA, but we would like to be able to go
as low as 5 kV for some work on paper supports and thin bark. We
often take a full montage of the painting which may involve 20 or
more exposures in succession but then not use the machine again for
several months.  Our lead lined box has been tested and is safe up
to 80 kV, so I don't care if it goes above that because it raises a
series of safety issues and I am better off hiring in an industrial
radiographer for such investigations.

I have also been in contact with the company in Japan that makes the
Softex X-ray unit which would seem to suit our purposes- but I have
not found anyone who has direct experience with the unit I am
interested in (the K-2 portable unit).  I first looked into this
unit about 15 years ago, so it has been around for a while and this
raises the concern about whether the power source stability is up to
scratch.

Does anyone on the list have recent experience with finding such a
unit?  Any considered advice on the power stability issue would be
gratefully received. And finally, has anyone used the Softex K-2
unit for radiography of paintings that can discuss their experience?

Thomas Dixon
Chief Conservator
National Gallery of Victoria
Melbourne Australia

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                  Conservation DistList Instance 13:17
                 Distributed: Thursday, August 26, 1999
                       Message Id: cdl-13-17-006
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