Re: Yellow pigment stain: (Was: Re: Sodium Bisulfite

I don't have pigment staining issues, and I use cyanotype as my first
layer for tricolor. There are (at least) four likely answers:

The sizing being wrong: not being a high enough percentage or not warm
enough or not enough hardening.

The paper being too soft (releasing the sizing too easily).

The wash water being too hot (releasing the sizing too easily).

Expecting "perfect paper white" in a gum print. In "my" experience
there is always some slight tone in the "white" areas. I don't think
that is the issue under discussion, as he can get good whites if he
doesn't do the cyanotype first.

Wait...... I just thought of a 5th possibility....... Some folks use
an acid bath for the first 1/3 of the cyanotype development/wash. I
found with my paper that the acid created a bleed problem. I don't know
what it might do to the gelatin sizing?

You could simply re-size after the cyanotype, but that is a "pain"!

On Wednesday, August 25, 2004, at 12:28 PM, Katharine Thayer wrote:

> kateb@paradise.net.nz wrote:
>>
>> Quoting Katharine Thayer <kthayer@pacifier.com>:
>>
>>>>>
>>>> Same process, same paper, same pigment, same everything also same
>>> negative
>>>> but the yellow pigment was applied before the cyanotype and NO
>>>> stain.
>>>> Any explanation?
>>
>> Here's my 2 cents worth: what if the process of applying the cyan
>> first
>> affected the paper sizing?...then it would be quite likely that the
>> yellow
>> pigment applied after the cyanotype would stain the paper.
>> Just a theory.
>> Kate
>
>
> Yes, I think that's a likely explanation, in fact I think that's what
> I
> was getting at when I said that if everything including the pigment
> concentration was the same, then it was probably sizing-related,
> although I haven't heard that people who use cyanotype as a first coat
> regularly need to re-size before putting on the gum coats.
> kt
>
>
--------------
Tom Ferguson
http://www.ferguson-photo-design.com
Received on Thu Aug 26 08:45:10 2004