[alt-photo] Re: Gum over cyanotype question

[Christina Anderson]

Matt,

As we always say on this list, YRMV.

To my way of thinking: Tween is used as a surfactant to allow a solution to sink into the paper fibers. Cyanotype, Ware's cyanotype, can benefit from an addition of Tween. So can argyrotype. But gum seems counterintuitive to me.

If you think of it this way: we use sizing to prevent the gum layer from sinking into the paper (along with the pigment). We use thicker gum to prevent the solution from sinking into the paper. 

But what do I know--maybe someone doing gum over platinum finds some reason to use Tween--it breaks up the viscosity of the solution or whatnot who knows. 

There are some who use/used a small addition of Everclear alcohol in their mix or Miracle Muck (some form of PVA if I remember off the top of my head---designed to make the layer stick more again if I remember) but I have never found a need to make additions to the gum layer aside from a little more gum, a little more water, a little more dichromate, a little more pigment. Or less of any or all as the case may be.

OH, maybe Tween might help with fisheyes in the coating layer!! Hmmm...

I have well water as well. 

Interesting you have not found prolonged exposure necessary with black. My guess is your black layer is thinner/less opaque than mine. An old pictorialist tradition was to use a thick gum/highly pigmented black layer with super long exposure and then good development to get one-coat gums. I find the trick is to use enough black for density but not too much because flaking occurs. I have not yet mastered this, though...on my list of things to do. With the one coat--no sizing, no shrinking, and if I remember Buxton/Ashton Platinum was the recommended paper when this discussion was going on.
Chris

Christina Z. Anderson
christinaZanderson.com

On Feb 29, 2012, at 5:45 AM, Willen, Matthew S wrote:

> Thanks Chris, it's been enjoyable watching all the responses, and I was
> wondering to myself yesterday if my question had in fact been answered.
> 
> I appreciate the suggestions. I've noticed the prolonged exposure with the
> burnt sienna and yellow. Not so much with black though.
> 
> Just wondering why you capitalized NO in the NO tween in the gum layer?
> Was that for emphasis? Is there an incompatibility between tween and the
> cyanotype?
> 
> One post had mentioned alkalinity of the water perhaps being suspect. I
> have well water, and all of the bedrock around here is limestone, and we
> have had tons of rain in the past few months, and so I think that may be
> worth looking into, for a host of reasons.
> 
> Anyway, I have a couple more days of teaching to progressively smaller
> classes before our spring break begins. Then I'll have some time to tease
> some things out. 
> 
> Thanks. Matt
> 
> On 2/28/12 1:41 PM, "Christina Anderson" <zphoto at montana.net> wrote:
> 
>> Matt,
>> I haven't read all the answers yet, so forgive me if this has been
>> answered; trying to clean out my inbox.
>> 
>> Burnt sienna for me takes a LONG exposure. 15 minutes is even not too
>> long. I don't know why this is the case--whether an earth pigment is more
>> opaque to light or not, but I find that yellow, burnt sienna, and black
>> expose from longer to longest in that order, and though I choose a
>> standard printing time around 6 minutes, thalo is happy with 4 or 5,
>> magenta 5 or 6, yellow 9, burnt sienna a sort of whoops I left it in the
>> UVBL longer so what, and black 9-15 as well. I know this sounds really
>> loose and unscientific, but I am just not so rigorous when my timer goes
>> off to get back into the dimroom and remove the contact frame from the
>> UVBL unit. But I will say that actually I have tested all colors with a
>> step wedge and found this to be true as well.
>> 
>> It is hard to be exact about this because I find that gum can expose at
>> all kinds of minutes/choices. I use a 6 minute ballpark because it
>> provides a layer that is very stable in development and will allow some
>> spray development in the beginning five or ten minutes.
>> 
>> I use 15% ammonium dichromate 1:1 with gum/pigment.
>> 
>> I have never had the cyanotype layer determine whether or not the gum
>> sloughs off or not.
>> 
>> Any part of the cyanotype that is covered by a gum layer does not wash
>> out for me.
>> 
>> NO tween in the gum layer.
>> 
>> Slickness and sloughing off in my experience is more determined by too
>> thick a layer of gum, not enough exposure, too much sizing.
>> 
>> Hope at least one of these points helps.
>> 
>> Chris
>> 
>> Christina Z. Anderson
>> christinaZanderson.com
>> 
>> On Feb 27, 2012, at 8:52 AM, Willen, Matthew S wrote:
>> 
>>> Hi All,
>>> I am working on some duotone prints using a cyanotype layer on the
>>> bottom and gum layer of an umber or sienna over the top. I'm using a
>>> stock solution of cyanotype from B/S. A couple of things happen: 1) I
>>> find that the gum layer doesn't stick particularly well to the
>>> cyanotype, it almost peels off; and 2) even though I wash throughly and
>>> all the cyanotype layer to dry well, I lose a lot of the density of that
>>> layer in the extended gum wash. Any suggestions? Perhaps some tween in
>>> the gum layer? I've also developed the cyanotype in a Hydrogen
>>> peroxide/H20 solution. Might that make it more slick? Thanks.
>>> 
>>> Matt
>>> _______________________________________________
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>> 
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