Re: Gum: Pigment stain and exposure

No problem; I'm glad you asked for the clarification and that I was
able to clear up the misunderstanding. I assumed it was understood
that the discussion of this anomalous result was within the context
of the stain tests on some 20 different papers that I described
yesterday; without that understanding it could seem confusing
standing on its own. And perhaps I didn't make it clear enough that
the reason I was making a special point of emphasizing that
contradictory result was simply as an illustration of how misleading
single observations can be. At any rate, if it didn't seem clear,
then obviously I didn't make myself as clear as I thought I had.
Katharine

On Aug 4, 2006, at 3:37 PM, Loris Medici wrote:

> Thanks for clarifying.
>
> "Same pigment mix" doesn't necessarily mean "same stock soln." - at
> least in my understanding of english (which is evidently poor) - it
> can be understood as "same pigment/gum ratio" or "same formula" too
> (maybe a side-effect of translation to turkish). The only
> information hinting you were using a stock solution was "(well-
> stirred)" but since the information wasn't clear to me / I was
> uncertain and confused (maybe completely caused by my poor english
> comprehension!?), I needed that you clarify.
>
> The chronological order also wasn't much clear; I took as if you've
> made two exposures on two separate pieces of paper (that were cut
> from the same sheet) and the stained one was the second piece.
> (I've read the original paragraph again and I still understand it
> exactly I described above...)
>
> Anyway, now I'm sure there won't be any other confusion about what
> you meant. :)
>
> Regards,
> Loris.
>
> ----- Message from kthayer@pacifier.com ---------
> Date: Fri, 04 Aug 2006 13:38:31 -0700
> From: Katharine Thayer <kthayer@pacifier.com>
> Reply-To: alt-photo-process-l@usask.ca
> Subject: Re: Gum: Pigment stain and exposure
> To: alt-photo-process-l@usask.ca
>
>
>
>>
>> On Aug 4, 2006, at 10:44 AM, Loris Medici wrote:
>>
>>
>>> Hi Katharine, thanks for sharing experience.
>>>
>>> My question is: have you made fresh gum / pigment mixes for each
>>> printing or you just used a stock gum / pigment solution?
>>>
>>
>> The gum/pigment mix was the same stock mix in both cases; that's
>> why I
>> specified that it was the same mix. I didn't mean it was mixed from
>> the same formula, I meant it was poured from the same stock mix,
>> well-stirred before each draw. All the test strips from the same
>> day
>> as the anomalous stained test print on acrylic medium were printed
>> from
>> the exact same emulsion. I printed some ten sets of test strips
>> that
>> day and it was only two or three that stained, and not the last ones.
>> And I printed another ten the next day, from the same stock mix,
>> with
>> similar results; a few stained, but most didn't, and the ones that
>> stained were randomly distributed throughout the day's printing.
>>
>>
>>> If the latter can we conclude that the pigment does something to
>>> the gum which leads to staining?
>>>
>>
>> No, as I said above, there's nothing in the data that would lead
>> one to
>> that conclusion. But maybe you've missed my point, which was that
>> concluding anything from one test print is not a good idea. The
>> reason I brought up this contradictory result was to show how
>> misleading it can be to draw conclusions from one observation; you
>> need
>> a generous sampling of observations from the distribution of possible
>> results before you start drawing conclusions.
>>
>> But to answer your question about whether stock pigment/gum mixes
>> that
>> sit for a long time CAN change in such a way that leads to
>> staining: it
>> depends on the gum. I've found that Daniel Smith premium gum doesn't
>> sit well; it tends to dry out over time; as a result the ratio of
>> pigment to gum does go up and staining can occur. But this is
>> something that happens over months, not overnight. But pigment/gum
>> mixes of seldom-used colors that were mixed ten years ago with the
>> old
>> Photographers' Formulary gum are still as fresh and liquid and
>> print as
>> stainfree as the day they were mixed.
>>
>> Katharine
>>
>>
>>
>>>
>>> TIA,
>>> Loris.
>>>
>>> ----- Message from kthayer@pacifier.com ---------
>>> Date: Fri, 04 Aug 2006 09:31:00 -0700
>>> From: Katharine Thayer <kthayer@pacifier.com>
>>> Reply-To: alt-photo-process-l@usask.ca
>>> Subject: Re: Gum: Pigment stain and exposure
>>> To: alt-photo-process-l@usask.ca
>>>
>>>
>>>
>>>
>>>> Another thing to ponder: in my stack of oddball pieces of paper,
>>>> there was a quarter-sheet of Arches Aquarelle that had been
>>>> sized with
>>>> acrylic medium. I had cut a piece off this paper the day before
>>>> and
>>>> printed a small tricolor on it from a file an offlist
>>>> correspondent had
>>>> sent me to try to figure out a problem he was having with his color
>>>> balance. The tricolor printed perfectly: no stain whatever on
>>>> any of
>>>> the layers, including the middle layer which was the same mix of
>>>> PR209
>>>> I used for the test strips described below. (The file as he
>>>> created it
>>>> had a border around the image which printed paper white, so any
>>>> stain
>>>> would have been very easy to detect, and this border was pure paper
>>>> white after the three layers). But when I cut another piece off
>>>> the
>>>> same sheet of paper and coated it with the same PR209 mix for these
>>>> test strips, I got immediate and irrevocable stain; it was one
>>>> of those
>>>> where you know on the first brush stroke that you've got stain; the
>>>> paper speckles immediately in a way that you can tell is going
>>>> to be
>>>> permanent.
>>>>
>>>> Why it would stain in one case and not in the other, when
>>>> everything is
>>>> the same: the exact same piece of paper, same pigment mix
>>>> (well-stirred) same amount of the same dichromate, coated area
>>>> about
>>>> the same size in both cases, same amount of brushing-smoothing,
>>>> same
>>>> light, same environmental conditions, and the exposures for the
>>>> print
>>>> were within the range of exposures for the test strips. But if the
>>>> very same things can yield such different results for the same
>>>> person,
>>>> it should hardly be surprising that different things yield wildly
>>>> different results, or that different people using the same
>>>> things often
>>>> get different results. Just another reminder that one test does
>>>> not a
>>>> finding make...
>>>> kt
>>>>
>>>>
>>>> On Aug 3, 2006, at 1:47 PM, Katharine Thayer wrote:
>>>>
>>>>
>>>>
>>>>> Okay, here's something to wake y'all up, since people are
>>>>> getting restless about getting no mail from the list:
>>>>>
>>>>> I've been printing PR 209 (quinacridone red) at four
>>>>> exposures, from underexposed to overexposed, on samples of
>>>>> all different kinds of paper. (I've got a little stack of
>>>>> paper odds and ends that I'm trying to use up). My goal was
>>>>> to try to see if it's true, as is often alleged here, that
>>>>> stain is related inversely to exposure, in other words that
>>>>> underexposed gum is more likely to stain than gum that has
>>>>> received more exposure. I figured if it were true, this
>>>>> effect would have to show up if I did a bunch of test strips
>>>>> at different exposures. After a couple of days of this, I
>>>>> have about 20 sheets of paper with four test strips on each,
>>>>> exposed at 1, 2, 3 and 4 minutes. Some of the papers are
>>>>> stained, some aren't. But in every case where there is
>>>>> stain, the stain is even across all exposures; there isn't
>>>>> more stain where it's less exposed (nor is there more stain
>>>>> where it's more exposed). The stain is simply constant
>>>>> across the entire coated area on the paper, which tends to
>>>>> support what I've said before, that stain is independent of
>>>>> exposure. All of these papers were developed for 1.5- 2.5
>>>>> hours, since they were developed for the most-exposed strip,
>>>>> which was well over-exposed. The variation in the time
>>>>> required to develop the 4-minute exposure reflects the
>>>>> difference in speed between the different papers. Mark, I
>>>>> think, was asking a while ago if there are processes other
>>>>> than platinum in which, everything else held constant,
>>>>> different papers print with different speeds. I answered
>>>>> "Yes, gum." This experiment shows the truth of that
>>>>> assertion. I wish I could scan these for you, but my scanner
>>>>> is still in the shop.
>>>>>
>>>>>
>>>>> A result worth noting: A piece of Lana that had been sized
>>>>> with glutaraldehyde stained an overall soft pink, while
>>>>> glyoxal-sized paper stained not a whit, nor have I ever had
>>>>> glyoxal give pigment stain. I'm not drawing any particular
>>>>> conclusion from this ; it's just more data for the collective
>>>>> database.
>>>>>
>>>>>
>>>>> Katharine
>>>>>
>>>>>
>>>
>>>
>>>
>
>
> ----- End message from kthayer@pacifier.com -----
>
>
>
Received on 08/04/06-05:13:58 PM Z