[Alt-photo] Outgassing in contact-printing siderotypes

Mike Ware mike at mikeware.co.uk
Mon May 19 13:52:17 UTC 2014


Greetings Jennifer,

Localised blurring  - which is why I spoke of "bubbles" - rather than a gas layer causing uniform overall loss. 
I don't think this forum allows attachments, so I've put an example - a test of New Cyanotype - in my Public Dropbox, which you can download here:

https://dl.dropboxusercontent.com/u/47727259/Soft_spots_cyano.jpg

This test was originally made for a quite different purpose. I was dismayed when I saw the blobby numbers on the Stouffers, but put them down at the time to a poor contact frame. Now I know better.
The printing paper was backed with a Mylar plastic sheet. When it is backed with felt, the blurring disappears.
This is a "bad case" example because, as you can see, nearly half the area is exposed to Dmax - rather more than most normal images.
The exposure was made to a Philips 'Cleo' facial solarium, which has an array of six 40 cm UV fluorescent tubes about 10 cm away.
When I expose the same target in its contact frame to a NuArc there is no visible blurring.
I've got similar tests showing this effect for Argyrotype, New Chrysotype, Platinotype and Palladiotype.
All good wishes,

Mike


On 19 May 2014, at 13:56, Darkrooms, Department of Art wrote:

> Mike,
> 
> Thank you for sharing this information.  I am curious, Does the outgassing
> create localized or global loss of sharpness?  Would you be able to share
> an example print?
> 
> Thank you,
> Jennifer M. Gioffre
> Teaching Support Specialist



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