[Alt-photo] Re: GUM: problematic yellow?

[Diana Bloomfield]

Hi Luciano,

I'm so glad you manage to get some of the Fabriano and work with it, and that you like it.  It is pretty amazing paper, isn't it?  

That's interesting about the yellow.  I know people always say they often have trouble with the blue pigment, but I never hear anyone talk about problems with yellow.  But I never had a problem with blue-- not sure why-- but I always always seemed to have issues with yellow, until someone (on this list, I think) suggested Quinacridone Gold for yellow.  I can't remember now which yellows I used that gave me so much staining-- they all seemed to as I remember-- but ever since I switched over to Quinacridone Gold (Daniel Smith or M. Graham), I haven't had a problem.
I also don't make stock solutions, so can't help you there.  But my (unscientific) thought is that it's the pigment itself.  If you can find the Quinacridone Gold somewhere, it would work for you.  I also like it as a yellow layer-- as it's not so much an in-your-face-yellow-- as it is a rich gold.

Diana




On Feb 5, 2014, at 12:27 PM, Luciano Teghillo wrote:

> After Diana suggestion (thanks again) I was able to source some Fabriano
> Artistico soft-press and I was able to print some exposure tests. The paper
> is great! I am not getting any stains, and finally I am printing something,
> even if they are only step wedges without having to pre-shrink, size, etc.
> etc.... The final test will come as soon as I can print more layers....
> 
> So far no problem with blue
> (http://www.lucianoteghillo.com/images/scan-blue.jpg) and red
> (http://www.lucianoteghillo.com/images/scan-magenta.jpg) but yellow it's not
> printing correctly, at least that's my impression.
> 
> After the first test
> (http://www.lucianoteghillo.com/images/scan-yellow1.jpg) with the usual
> exposure times used for blue and magenta (from 1 minute to 3.30 minutes in
> 30 seconds intervals), it looked like I was not reaching maximum "black" but
> also the steps didn't look as defined as with the other colors. So I decided
> to print one more test with exposures of 16, 32 and 48 minutes
> (http://www.lucianoteghillo.com/images/scan-yellow2.jpg). I think this
> second test is event worst than the first.
> 
> Now everything is the same: same gum, same potassium dichromate, same
> process. I mix a stock solution with 15ml tube and 45ml of gum, which I then
> further dilute as needed. In the case of yellow, I mix 1ml of stock solution
> with 1ml of gum and 2ml of 12% potassium dichromate.
> 
> The watercolor used for yellow is Maimeri Blue, Primary Yellow, PY97
> (Arylide yellow, also known as Monoazo yellow).
> 
> This might be important or not, but I noticed some separation between gum
> and pigment in the stock solution bottle. If I let the bottle rest for a
> day, I can see a ring the color of gum 1/4" thick on top, something I did
> not notice with the other colors.
> 
> Do you have any advice? I do not have other yellow tubes from other
> pigments/brands but I could look for it. It just seems strange that I cannot
> print this color!!!
> 
> Thanks,
> Luciano
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