[alt-photo] Re: pigment problem

[Katharine Thayer]

P.S. On second thought, it sounds like what you're saying is not that  
the gelatin is cooling and gelling, but that it's hardening before it  
gets brushed on, which is a different issue.   In which case, maybe 1  
drop formalin instead of two?  But I'd check first and make sure it's  
not that it's cooling down and setting up; that's the easier problem  
to solve.


On Feb 7, 2011, at 4:57 PM, Katharine Thayer wrote:

> Ah, then I'm sure of it.  If the gelatin is setting up while you're  
> brushing it on, it's almost certainly making too thick a gelatin  
> layer, which may fill up the tooth to the extent that there  
> wouldn't be room for three gum layers to hang onto the paper  
> fiber.  You need to keep the gelatin warm throughout the sizing  
> process so that it will soak deeply into the paper rather than  
> sitting on the surface.   I keep an extra microwave oven in my  
> sizing area and reheat the gelatin (very gently on low power)  
> occasionally to keep it above 120 F but under 140 F.   Others keep  
> it warm in a vacuum jug or with a water bath; whatever it takes.  I  
> would almost bet money that that should fix the problem for you.
>
>
> On Feb 7, 2011, at 4:10 PM, Julian Smart wrote:
>
>
>> Hi Katherine, thanks for the reply.
>>
>> I had sort of come to the conclusion that it may be a sizing  
>> issue. Trouble is I have no  precedent for my problem in that I  
>> have only just started to use this paint and have just recently  
>> modified my sizing technique. I now size with a hardened gelatine,  
>> that is I add 2 drops of formaldehyde to a 100ml of gelatine just  
>> prior to brush coating the size. I really wouldn't have thought  
>> that this would be a problem, or cause problems with different  
>> pigments, though I have noticed that the gelatine has hardened  
>> enough by the time I am sizing my fourth sheet to not allow a  
>> decently smooth coat.
>>
>> Tomorrow I will try a different pigment, probably the Indanthrone  
>> you suggest and see how it goes.
>>
>> Julian.
>>
>>
>>
>>
>>
>> ----- Original Message ----- From: "Katharine Thayer"  
>> <kthayer at pacifier.com>
>> To: "The alternative photographic processes mailing list" <alt- 
>> photo-process-list at lists.altphotolist.org>
>> Sent: Monday, February 07, 2011 11:08 PM
>> Subject: [alt-photo] Re: pigment problem
>>
>>
>>
>>
>>> Hi Julian, well, first a point of clarification about pigment  
>>> names: you're not printing with indigo pigment.  Indigo is PB 66,  
>>> a pigment  so fugitive that it is no longer used in any  
>>> watercolor brands  (Winsor & Newton was the last to discontinue  
>>> it, about five years ago  or so, if I remember right).  All  
>>> paints named "indigo" nowadays  aren't actually indigo but are  
>>> convenience mixes of other pigments,  mixed in an effort to  
>>> replicate an indigo hue, and to follow  traditional naming  
>>> convention, they should all be named "indigo hue"  rather than  
>>> "indigo,"  IMO.  But never mind about that.
>>>
>>> While I often mix pigments myself for my own purposes, I try to  
>>> avoid convenience mixtures where I don't have any choice over  
>>> what pigments  are used.   I have found some pigment mixtures  
>>> that produce a split  tone effect in themselves (I'd have to go  
>>> back to the archives to be  reminded of what those were, since  
>>> I've never gone on to use them in  my work) in other words one of  
>>> the pigments in the mix will be more  evident in the lighter  
>>> tones and the other pigment in the darker  tones.  If you're  
>>> interested in what those pigments were, I'm sure I  reported it  
>>> to the list when I made that observation, so it should be  in the  
>>> archives somewhere.
>>>
>>> What you've got here is phthalo mixed with quinacridone rose,   
>>> apparently to shift the blue more to the red side, plus lamp  
>>> black to  darken it. If it were me and I were looking for an  
>>> indigo-like hue,  I would use a single pigment that is close to  
>>> that hue rather than a  mixture. Indanthrone, PB 60, is a very  
>>> close approximation to indigo.
>>>
>>> All that said, I'm not entirely convinced from your description  
>>> that  your problem is related to pigment, however; it sounds to  
>>> me more a  problem of adhesion, or tooth, in other words that the  
>>> layer isn't  attaching to the paper as it should.  It would help  
>>> to be able to see  exactly what you're talking about, but if the  
>>> layer is hardening  properly but then frilling and lifting off,  
>>> that's most likely to be  related to an inadequate "purchase" of  
>>> the gum layer on the paper.   So that's the line I would pursue  
>>> in trying to solve the problem,  look at issues of sizing, paper,  
>>> prior layers, to see if there's  something that is interfering  
>>> with there being enough tooth left  available to attach that  
>>> third layer.
>>>
>>> Katharine
>>>
>>>
>>>
>>
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