[alt-photo] Re: pigment problem

[Loris Medici]

While that may perfectly work, a separate formalin bath has the risk of
increasing your exposure to formaldehyde - due to the larger volume (=more
formalin) and area of the hardening bath...

Julian, to me, your problem seems not one related to the hardening /
hardener. I remember you wrote that your gelatin + hardener mixture stays on
a hot plate (or water bath?) and doesn't show any signs of hardening within
20 minutes. Maybe the problem is in the method of application?

- What kind of brush are you using? (My guess: A standard bristle brush?)
- Do you size indoors or outdoors? (Again, my guess: Outdoors, or a
relatively cold place?)

I use sponge brushes, soak a generous amnt. of gelatin + hardener mixture,
and brush it quickly and evenly on the paper. I dip the brush another time
into the solution if the amnt. in the first pass wasn't enough. I try to do
it very quickly and my papers are at room temperature. (I size indoors...)
Sizing a half imperial sheet wouldn't take more than 1-2 minutes in my
workflow. (At max! More like ~1 minute usually...) Your expression "20
minutes for 4 1/2 imperial sheets" makes me think you're working quite
slowly, maybe because you don't use a sponge brush can holds a generous
amnt. of sizing solution... The slower you work, the more you risk gelatin
setting / uneven application.

Try to work a little faster and make sure the paper is not too cold while
you apply the sizing...

Hope this helps somehow. (I absolutely don't have any clue about your -
actual - pigment related question...)

Regards,
Loris.

P.S. I use a lot more hardener than you BTW; 5-10 drops per gram of
gelatin... (15-20 drops per 100ml 3% solution.) Therefore, I don't think
it's the hardener.


-----Original Message-----
From: alt-photo-process-list-bounces at lists.altphotolist.org On Behalf Of
Tomas Sobota
Sent: Wednesday, February 09, 2011 10:57 AM
To: The alternative photographic processes mailing list
Subject: [alt-photo] Re: pigment problem

Hi Julian,

Well, it seems that the pigment problem is solved, but you still seem to be
having sizing issues. Why don't you just coat with plain gelatine and harden
later with a formalin solution? It is slightly more work, but you will never
have the problem of the gelatine hardening too fast. I apply two coats of 3%
gelatine and harden after they are well dry.

cheers
Tom


On Wed, Feb 9, 2011 at 12:20 AM, Julian Smart
<juliansmart at virginmedia.com>wrote:

> So I have now done a coat of Indanthrone PB60 on two seperate prints 
> and found no problems whatsoever. I used a diluted pot. dichromate 
> solution
> (6.5%) and gave my usual shadow exposure of 3 mins dead.  The pigment 
> gave me a very nice split that I had been after, but curiously the 
> prints  were effectively overexposed (enough that I could brush away 
> the coating at will without destroying what I thought would be a very
delicate layer).
>
> I am now of the opinion that the W+N Indigo paint I am using has a 
> binder made from a gum that would effectively print much slower if I 
> were using it for my main emulsion. The paint does seem to be slightly 
> more sloppy than that from most other tubes, and I can't really 
> imagine that the binder will have that much of an effect when mixed 
> with my normal gum but I think I can now rule out paper sizing as an
issue.
>
> I will record that I now have two very nice gumprints, both with the 
> colour split I required but am still somewhat puzzled by the behaviour 
> of the Indigo paint I originally tried.