Re: cyanotype question

[Joseph Smigiel <jsmigiel@net-link.net>]

I've not been following this cyanotype discussion very closely so  
forgive me if what I'm about to relate has already been discussed.  I  
recently ran a few cyanotype tests on Cranes' Kid Finish white and  
ecru to test the effect of varying proportions of FAC and KF on  
contrast and speed.  I found rinsing the prints in 2% citric acid  
caused bleeding as this scan shows:

http://my.net-link.net/~jsmigiel/images/technical/ 
cyan_proportion_test.jpg

The scan compares the standard cyanotype formula on white & ecru  
Cranes' at one exposure (1120 units on a Nu-Arc mercury unit) and  
processed together in either plain tap water or the 2% citric acid  
bath for the same amount of time.

I'm surprised by the short scale of these and will have to check the  
water pH.  A later test run by a student indicates just a splash of  
2% acid in the rinse will retain the deeper blue color without  
causing the stain.

Joe


On Dec 13, 2008, at 10:15 AM, Christina Z. Anderson wrote:

> Hi Loris,
> No,  haven't tried acidifying the paper, tho I do have both citric  
> and oxalic.  But in practice, if I were to do a plain cyanotype I  
> wouldn't use that paper.  It just produces a kind of plain blah  
> blue print.
>
> My interest in the bleeding was wondering if the FAC was the  
> culprit, if its molecules are the bigger ones that maybe don't sink  
> in as well into the paper fibers, because it is the increased FAC  
> that bled.
>
> It's blizzarding and 12 degrees outside now; good day to stay in  
> and print. If I could summon up enough energy at this end-of-the- 
> semester.
> Chris
>
>
> Wow, thanks much for that Christina. Definitely useful / helpful...  
> As for
> bleeding with FAEW; have you tried to acidify the paper? I get none or
> very little (depending on exposure) with acidified FATW.
>
> Regards,
> Loris.