cheers
-steve
p.s. no I didn't wait up just to post these :-)
------- Forwarded Message
From: Philip Jackson <pjackson@nla.gov.au>
To: alt-photo-process <alt-photo-process@vast.unsw.edu.au>
Subject: Re: Woodburytype i.d.
Date: Tue, 27 Feb 96 18:31:00 PST
I wrote:
>>perhaps
>>the only way to non-destructively determine whether the plates in Terry's
>>book are woodburytypes might involve using x-ray diffraction
>>spectroscopy to test for traces of chromium. Some probably remain in a
>>carbon print (Luis?), but the 'ink' used to produce woodburytypes would
>>consist solely of gelatine and colouring matter.
and Luis commented:
>Not necessarily. Chrome-green was a very popular pigment. I have seen
>many green carbon and bromoil prints, though not woodburytypes. Most
>colors were produced by a mixture of pigments.
When I made the suggestion about testing for chromium I'd forgotten an even
more important factor - woodburytypes were hardened in chrome alum. Can
x-ray diffraction differentiate between different chrome compounds:
dichromate sensitzed gelatine, chrome green pigment suspended in gelatine,
and chrome alum hardened gelatine? Maybe John's suggestion about looking for
lead (or lubricating oil) transferred from the mould provides a much better
solution. The burnishing of Woodbury paper John mentioned was accomplished
with shellac.
>This said, I have wanted for a long time to produce a number of pigment
>prints using well documented old methods and then see if X-ray diffraction
>can easily determine which is which. I hope to get this work done in time
>for my next carbon book possibly next year.
Sounds like a very worthwhile project. Are you thinking about postponing
your trip to Paris so you can buy your own x-ray spectrometer? (:-)
Cheers,
Philip
------- End of Forwarded Message