[alt-photo] Re: further cyanotype observations

[Peter Friedrichsen]

The speed and shade difference suggests a pH difference in the paper 
as both traditional cyanotypes (Citrate based) and the ware formula 
(Oxalate based) are fastest at a lower pH. Also note that the slowest 
papers have a tint of red in them versus the more cyan shades of the 
faster papers. I think perhaps that the alkalinity is converting some 
of the prussian blue to ferric hydrate and ferric hydrate is a brick 
red and it may be that which shifts the colour, but I am not really sure.

Peter Friedrichsen


At 10:33 AM 26/02/2012, you wrote:
>Dear All,
>
>I have posted a visual at the URL below which shows the different 
>paper "speeds" with traditional cyanotype. I have tried to be as 
>consistent as possible with humidity, room temp, rest time before 
>exposure, drop count, development time. All exposures are 15 
>minutes--my usual "baseline printing time" for cyanotype to arrive 
>at my "standard printing time" for that paper. With Fabriano AEW I 
>usually up that BPT to 20 minutes.
>
>  At any rate, it might be a helpful visual for you on how different 
> papers have different speeds with cyanotype, as well as different 
> graininess. Traditional 1:1, Edwards UVBL light box. You will note 
> why I was so surprised at Buxton's speed: maximum black comes at 
> step 8 on a 31 step tablet, whereas on other papers it may come at 
> step 3--a difference of 1 2/3 stops. That would result, once b+f of 
> step wedge and pictorico is taken into account, in a difference of 
> 4 versus 11 minutes.
>
>The little arrows on the visual, if the web shows it, should point 
>to the first line of demarcation visible between steps, so above the 
>line is the first max black.
>
>Masa, Buxton, Platine, and Cranes Cover are the clear winners in the 
>grain category IMHO. Platine is just an all around great paper for a 
>lot of processes. I also can't believe how thick and sturdy Cranes 
>is once wet. It thickens quite nicely but remains very smooth. The 
>others that grain I would be more careful with the brush choice and 
>amount of solution next time (more).
>
>Some of the papers are cream colored base, some are white. A couple 
>bled (masa and BFK175gsm I think). The BFK is not the normal BFK, btw.
>
>Still have another batch of papers to test, but you get the 
>picture...nothing so exciting as Charles' nice gum prints to see, 
>just some boring step wedges, but anyway.
>
>One last thing: I mixed up my own homemade (not store-bought) Ware's 
>formula and it, in fact, clears nicely, so the b---ch clearing 
>problem was most likely due to old/contaminated chemistry in the 
>purchased product.
>
>Doug, will be interested to see what you think are the differences, 
>if any, between Cot320 and Platine :)
>
>Chris
>
>http://christinaanderson.visualserver.com/Text_page.cfm?pID=1953
>
>
>
>
>Christina Z. Anderson
>christinaZanderson.com
>
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