[alt-photo] Re: back again

[Loris Medici]

Matti,

With my old lightsource cyanotype exposures with (thin) paper negs were
around 60 mins. too. Therefore, I assume our conditions (combination of
lightsource, paper, emulsion...) are similar. With the same lightsource,
using paper negs and 10-15% (amm.) dichromate, my gum exposures were around
6 mins. (average), I never tried casein with paper negs but IME, at the same
conditions, casein was at least 1 - 1.5 stops faster than gum. So, I'm with
Christina here; 40 minutes sounds a little too much. ???

As a note: My casein layers were considerably thinner than my gum layers
FWIW...


-----Original Message-----
From: alt-photo-process-list-bounces at lists.altphotolist.org
[mailto:alt-photo-process-list-bounces at lists.altphotolist.org] On Behalf Of
Matti Koskinen
Sent: 24 Ekim 2011 Pazartesi 14:08
To: The alternative photographic processes mailing list
Subject: [alt-photo] Re: back again

Hi,
Yes
40 min. Same uv-light cyanos are one hour. But coating succeed with heavier
layer, then brushing and rolling as in tempera. Because heavier layer, even
40 min was not enough. Had to use sodium carbonate to get anything visible,
but that lost details too.
-matti