[alt-photo] Re: Multi coat Gum -3rd+ coats tends to wash off

[pfriedrichsen at sympatico.ca]

Loris et al,

I was attempting to produce very saturated layers and in that 
attempt, I increased the gum concentration in order to accommodate 
(without staining), the amount of pigment that was required. Once I 
reduced the gum and pigment concentration, the adhesion was improved 
and the top layer behaved.

I still have no understanding as to why there were no problems with 
these thick layers when laying down the cyan layer first.

Thanks to all for the assistance.

Peter


At 04:35 AM 02/26/2010, you wrote:
>I'm not sure if changing the order of layers does indeed help the emulsion
>to cling onto paper. (I don't think so but that's gum!)  My understanding of
>Keith's (highly plausible) practice comes from the fact that printing cyan
>first makes easy to register subsequent layers. Also what really ruins a gum
>print is often an error in the cyan layer (paraphrasing Keith - I agree
>completely), so printing it first will let you decide if it's worth to
>continue and/or allow to change your strategy before it's too late. (Again,
>highly plausible explanation; even if you don't follow their path exactly,
>it's very beneficial to listen to the masters...) The only disadvantage (if
>you like...) of this method is that you have to choose pretty transparent
>yellows and reds/magentas for subsequent layers - if not, you'll have a
>distinct haze over your dark tones. OTOH, that could change the look
>completely. May work for you or may not...
>
>If your emulsion doesn't leave the paper in bits and pieces (flaking that
>is), then you probably don't have to fiddle with pigment amounts.
>(Especially if you're happy with the colors you're getting.)
>
>IME, if you use a relatively thick coating solution, you definitely need to
>brush pretty harshly to be able to get a nice smooth and thin layer. Maybe
>you should try to lightly size the paper (with 3% hardened gelatin or
>diluted PVA size) to minimize the risk of staining.
>
>Play with the exposures a little bit - just as Paul mentioned. That could
>help indeed, in case it doesn't negatively affect your darks in the same
>time.
>
>What exactly is your coating solution's formulation? If it's gum/pigment +
>dichromate 1:1, you may try to add extra 1/2 to 1 part water and see how
>that works. (1 gum/pigment + 1 dichromate + 1/2 or 1 water...)
>
>Hope this helps & good luck!
>Regards,
>Loris.
>
>
>-----Original Message-----
>From: alt-photo-process-list-bounces at lists.altphotolist.org On Behalf Of
>pfriedrichsen at sympatico.ca
>Sent: Friday, February 26, 2010 1:16 AM
>To: The alternative photographic processes mailing list
>Subject: [alt-photo] Re: Multi coat Gum -3rd+ coats tends to wash off
>
>John,
>
>I reversed the layers by moving the cyan to the first layer rather than the
>last. Funny that this allowed the top layer (now magenta) to adhere well.
>There was a post that I found in the list archives of Sept 2008 by Keith
>Gerling who suggested printing cyan first.
>
>Now having said all of this, I still do believe that it shouldn't matter
>which color goes first in terms of adhesion so I suspect that the amount of
>dried gum left after development  must be in excess. I will do some
>adjustments by diluting the gum concentration, and if need be, the pigment
>load as well. Your suggestion of going over it with a dry foam roller may
>also be worth a try however I do find that the slightest pressure on the
>paper from a foam roller increases staining, a tleast that was my experience
>when I gave it a go some time ago.
>
>Peter Friedrichsen
>
>At 05:39 AM 02/24/2010, you wrote:
> >Hi Peter,
> >
> >Yes, there are some that don't size but you may get staining issues.
> >Also, when stretching and developing you may lose some of the manufacturers
>size.
> >It is gum compatible because it has a good wet strength and is
> >dimensionally stable.
> >
> >I use FAEW HP, sized with gelatine and have put down 7 or 8 layers on
> >one image. I'm with Loris here on the thickness of your layers. I find
> >I can get a very thin layer by coating with a foam brush and then using
> >a dry foam roller to even out the coating.
>
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