[alt-photo] Re: IDEA? NEW ALT PHOTO BOOK

[Keith Gerling]

A very nice summary, Katherine.  However, can you explain this?  In the
process of clearing the third or fourth layer of a print, I've had the
previous two or three layers suddenly go soft and slough off the surface (or
at least threaten to do so.  For instance, I might spray a print in an
effort to clear some highlight and see gum blow completely off the surface
wherever a larger droplet might hit).    I've never seen this happen with
gelatin sized prints.  in my experience, there has always been a sacrosanct
understanding between me and the print, that a cleared, hardened and dried
layer was "permanent" and would not loosen and go weak.  Any amount of
scrubbing on further layers would not disrupt the previous hardened layers.

If the gum is attaching to the fibers, and not to the PVA size, then it
would seem that this loosening would not happen. The effect I observe
appears very much as if the PVA sits BETWEEN the fibers and the gum, the PVA
softens, and the whole shebang lifts off.  I don't think gelatin and PVA
size in the same way.

Keith

On Fri, Apr 23, 2010 at 1:08 PM, Katharine Thayer <kthayer at pacifier.com>wrote:

> Whatever size is used,  the gum attaches to the paper fibers rather than to
> the size, so the material used in the size shouldn't make any difference to
> how the gum adheres to the paper.   Difficulties with size arise when the
> size becomes so thick or heavy that it clogs the surface fibers and leaves
> nothing for the gum to hang onto; then the hardened gum tends to slide off
> into the water.  This is true whatever size is used, and this is why the
> optimal dilution of PVA size is different for different papers, because
> different papers have different surface qualities, and the size needs to be
> diluted enough that it soaks into the paper leaving surface fibers ("tooth")
> open for the gum to attach to.  So no, the gum doesn't "sit" on top of PVA
> size any more than it does on top of a gelatin size.
>
> Paul: Since the unreacted dichromate and soluble gum wash off in
> development, there are no reaction products left in the finished and dried
> print, so there would be no purpose in exposing the dried layer to UV.
> IME, a print that's properly exposed and developed is entirely stable to
> rewetting.  If soluble gum is left in the print, in other words if the print
> is removed and dried while there is still soluble gum in the paper, then
> that soluble gum will continue to dissolve and change the print when it is
> rewetted, but if the print is properly exposed and developed, there will be
> no undissolved gum and the print will be entirely stable to water,
> containting only hardened (insoluble) gum.  If you think about it,  the
> permanence of a gum print is a function of the insolubility of the hardened
> gum.  If the print dissolves when wet, that's not a permanent print.
>
> Katharine
>
>
>
> On Apr 23, 2010, at 9:41 AM, Paul Viapiano wrote:
>
>  Christina...
>>
>> These are all very good questions.
>>
>> Personally, I like to put down at least two layers before PVA sizing. I
>> have noticed that the layer after the size has a harder time adhering, hence
>> I should probably expose more or develop for less time. But then again,
>> there are so many variables going on in any print, that I haven't taken the
>> time to try and pin it down.
>>
>> I think that someone (Keith Gerling) also mentioned a while back, that he
>> found layers were less stable when re-wetted. Would things be more stable if
>> we exposed the print to UV after drying each layer? Just a thought here...
>>
>> I don't know if the print really sits on top of the PVA any more than the
>> gelatin. I look at it as just helping the already-sized paper along as its
>> original size gets diluted with repeated soaking. This is all very
>> unscientific of me but is what I'm thinking.
>>
>> Paul
>>
>> ----- Original Message ----- From: "Christina Anderson" <
>> zphoto at montana.net>
>> To: "The alternative photographic processes mailing list" <
>> alt-photo-process-list at lists.altphotolist.org>
>> Sent: Friday, April 23, 2010 6:31 AM
>> Subject: [alt-photo] Re: IDEA? NEW ALT PHOTO BOOK
>>
>>
>>
>>  Bob,
>>>
>>> I think it could be a good thick chapter of a book...
>>>
>>> I am probably opening up a can of worms here...
>>>
>>> I've been using the Gamblin PVA size now and taught it to my class this
>>> semester in place of glutaraldehyde hardened 2.8% gelatin (6ml of 2.5% per
>>> liter), and it is a great teaching method and really user friendly.  Boy was
>>> my life easier--no hot plate, massive sizing day, mess, toxicity.  PVA you
>>> can just "size as you go". It is the "magic bullet" of teaching for sure.
>>>
>>> I use it 1+2 on Artistico.   I found more issues with staining with PVA
>>> than with glut/gelatin but that I think is specifically related to having to
>>> determine the dilution of PVA for each specific paper.  I almost think
>>> Fabriano might benefit from either a 1 + 1.5 or an intermediate layer of
>>> sizing between multiple coats. But at a point, then, PVA becomes too slick
>>> and plasticy.
>>>
>>> However, after having worked with it all semester I slightly prefer
>>> glut/gelatin.  **But** I am not sure I prefer the latter enough to go to all
>>> the trouble to do it.  With tray sized sheets gelatin is no big deal, but
>>> with 15x22 size sheets it is a pain. PVA wins, hands down, for
>>> user-friendliness.
>>>
>>> I will be finishing up two large gum projects this summer so we'll see by
>>> the end of summer how I feel--if I go back to gelatin in my own work, in
>>> other words.  I will continue to teach the non-toxic PVA method, but parts
>>> of me think I should still at least show students traditional sizing because
>>> of a concern I am feeling.
>>>
>>> My concern is this:  when I take a print out of the water to hang to dry,
>>> even the border of the print is what I would call "unstable"--meaning a
>>> fingerprint on it will mar it quite extensively in a way I have not seen
>>> with gelatin sized paper. Anecdotally, a rewetted PVA print SEEMS also less
>>> stable--layers still manipulatable.  Is that an issue?  I don't know. My
>>> question is does each layer you do of dichromated gum on top of a layer of
>>> previously hardened gelatin also affect the gelatin below (another colloid)
>>> and does it, in fact, affect a layer of PVA in the same way?  Or can the
>>> layer of gelatin even GET rehardened repeatedly with each succeeding layer
>>> of dichromated gum or is it hardened once and for all with the glut and that
>>> is it--successive layers do nothing?
>>>
>>> Or is this just a "hydrophilic" thing, or that gum is (how would you say)
>>> "attracted" to PVA in the same way it is to a surface of gelatin?  Are, in
>>> effect, PVA and gelatin truly interchangeable in sizing or is it possible
>>> that each layer of hardened gum has better adhesion to a layer of gelatin
>>> vs. a layer of PVA, probably only visible at the microscopic level?
>>>
>>> Maybe the scientists of the list can answer these questions and put my
>>> mind to rest, because my lurking fear is that the gum print on top of the
>>> PVA may not be as stable in the long run as one on top of gelatin.  A
>>> non-scientific test I will do in a couple months is soak a PVA'ed print and
>>> a gelatin-sized print, old ones, side by side, and scratch and see the
>>> results. But I don't know if that proves anything.
>>>
>>> I hope someone will come on list and say this fear is completely
>>> unfounded, that both sizings create equally stable final prints. But I am
>>> worried the gum print sits on top of the size instead of melds into it.
>>>
>>> I have no answers, just asking the hard questions....on this quest for
>>> the most perfect, easiest size.
>>>
>>> Now, as far as other processes aside from gum....salt...hmmm....
>>>
>>> Chris
>>>
>>>
>>> Christina Z. Anderson
>>> christinaZanderson.com
>>>
>>>
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