[alt-photo] Re: IDEA? NEW ALT PHOTO BOOK
Katharine Thayer
kthayer at pacifier.com
Fri Apr 23 19:23:01 GMT 2010
PS The only time I've seen something like what you're describing is
when I was printing on Yupo, which reminiscence reinforces (to my
mind) my suspicion that it's a problem of not having enough available
tooth.
On Apr 23, 2010, at 11:41 AM, Keith Gerling wrote:
> 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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