RE: Back-exposing on plastic (was: Re: Gum transfer

Dave,

As a carbon printer I can see two reasons why gum transfer, exposing
a gum emulsion from the rear, might be preferable to carbon.

1. You coat the emulsion using procedures that are familiar to gum
printers. And you can expose within a relatively short time of
coating. That is, you don't need carbon tissue, which has to either
be purchased, or made, well in advance of the printing session.

and

2. It is possible (but *not* certain) that you might have a bit more
control in development than with carbon.

Sandy

>I agree and though I think it is possible to do gum transfer, I do not quite
>understand what is the point of doing that (except maybe to show that it is
>possible). In my opinion, if one is interested in transfer, then just do
>carbon transfer. It is a process that is known to work nicely.
>
>
>Dave S
>
>-----Original Message-----
>From: Katharine Thayer [mailto:kthayer@pacifier.com]
>Sent: Monday, April 17, 2006 5:49 PM
>To: alt-photo-process-l@usask.ca
>Subject: Re: Back-exposing on plastic (was: Re: Gum transfer
>
>Hi Dave,
>No, I'm not transferring anything, that's why I changed the subject line, so
>nobody would get confused and think I was talking about gum
>transfer. I'm still back trying to replicate Marek's result of the
>other day printing a very thick heavily pigmented gum layer from the back
>and getting a more subtle tonality in lights and darks. It's not working
>for me at all, unfortunately, and I've spent the whole &* (%$ day on it.
>
>But I don't understand where this transfer business is going, all of a
>sudden, because I thought that Marek had demonstrated that you can get a
>better tonal scale with gum by exposing from the back (which I was very
>excited about but have not been able to replicate today). I personally love
>the way the print looks on the transparency, and would have no particular
>interest in transferring it anywhere. (2) But Marek, and Sandy, and Peter,
>are interested in gum transfer. But to transfer, it has to be exposed from
>the front, say Marek and Dave now. So I guess I've lost touch with what the
>point was, since you can get a better result printing from the front
>directly onto paper than you can get printing from the front onto plastic,
>(IME so far) so what would you be gaining exactly by printing from the front
>on plastic and then transferring it?
>Katharine
>
>
>
>
>
>On Apr 17, 2006, at 1:54 PM, Dave Soemarko wrote:
>
>> Hi Katharine,
>>
>> I am not sure if I am reading your procedure correctly, but are you
>> trying to develop the gum print on mylar first and then transfer it?
>> That is not how it is supposed to work. For transfer work, you expose
>> (from the front, not from the back), and then you can wet it,
>> transfer, and then develop (similar to carbon transfer, and that is
>> how Marek worked too as he described).
>>
>> Perhaps that explains why you didn't get the transfer to work in the
>> past?
>>
>> Actually gum transfer also shows that hardening is from top.
>>
>> I also have other emails that I will respond to on gum hardening, but
>> I will do that later in the week.
>>
>>
>> Dave S
>>
>> -----Original Message-----
>> From: Katharine Thayer [mailto:kthayer@pacifier.com]
>> Sent: Monday, April 17, 2006 3:47 PM
>> To: alt-photo-process-l@usask.ca
>> Subject: Back-exposing on plastic (was: Re: Gum transfer
>>
>> Okay. Well, so far I'm not getting it to work, so there must be
>> something different either in my materials or my method. I'm now
>> getting a good solid gum layer that is probably overexposed because it
>> takes forever to develop, but I'm getting really uneven results. I
>> have one print on mylar that is coming out quite high-contrast (losing
>> highlights) just
>> like a heavily-pigmented coating would be if it were front- exposed.
>> And another, that was coming out very well, very delicately
> > continuous- tone, but then, after 35-40 minutes of exposure, started
>> developing pinprick holes all through the gum layer, so the image is
> > all full of these little holes.
>> And contrary to your report, I'm finding that streaks and unevenness
>> of coating do show up in the print. (My coating is very heavy, lamp
>> black heavily pigmented and coated thickly so as to be completely
>> opaque.)
>>
>> I suspect that my problem is that I'm exposing too long and hardening
>> the layer all through (I don't get black gum coming off the top as you
>> described the other day, and it takes a long long time before gum
>> starts dissolving out of the less-exposed areas of the image). Maybe
>> for this method it's better not to harden clear to the top of the
>> layer. How long do you develop your back-exposed prints?
>> Katharine
>>
>>
>> On Apr 17, 2006, at 12:24 PM, Marek Matusz wrote:
>>
>>
>>> Katharine,
>>> I don't know much about the transparency material. Just a brand that
>>> I picked up in a local office supply store a while back.
>>> Marketed by HP. Come to think of it the transparency has a gelatine
>>> layer on one side for injet printing, so perhaps it was pr-coated,
>>> subbed or somehow prepared to accept gelatine layer. I soaked it in
>>> chlorox to soften the gelatine and the brushed it off. Both sides
>>> seem to be working the same.
>>> Thanks for posting the image
>>> Marek
>>>
>>>
>>>
>>>
>>>> From: Katharine Thayer <kthayer@pacifier.com>
>>>> Reply-To: alt-photo-process-l@usask.ca
>>>> To: alt-photo-process-l@usask.ca
>>>> Subject: Re: Gum transfer
>>>> Date: Mon, 17 Apr 2006 10:53:14 -0700
>>>>
>>>> Marek, you betcha I'll add your image to my site. I'm right now
>>>> trying to replicate your results with the thick heavily pigmented
>>>> coating, with some interesting, not 100% successful, results, but
>>>> the one that's soaking now looks promising. I've had a very
>>>> difficult time getting the very thick gum layer to stick through
>>>> development on untreated mylar, trying to replicate your
>>>> conditions, and have had to retreat to the scuffed mylar. I wonder
>>>> if your transparencies are made of some other more gum- accepting
>>>> material.
>>>>
>>>> Katharine
>>>>
>>>>
>>>>
>>>> On Apr 17, 2006, at 10:44 AM, Marek Matusz wrote:
>>>>
>>>>
>>>>
>>>>> There were a lot of interesting posts this weekend and I am going
>>>>> thorugh them now. I have done a few more gum transfer experiments.
>>>>> Here are some observations and issues.
>>>>>
>>>>> When exposing a gum layer through the substrate (glass, polyester,
>>>>> etc). This is "expose through the bottom mode" heavy pigment
>>>>> concentration is OK, coating imperfections are not that critical as
>>>>> the air bulles rise to the top, streaks in coating are also on the
>>>>> top. A thin image layer that adheres well to the substrate after
>>>>> development shows relatively few imperfections and looks
>>>>> suprizingly good. I have not done much more on that as I am waiting
>>>>> for a sunny weekend where I can experiment with some gum on glass.
>>>>>
>>>>> Gum Transfer.
>>>>> Here is how I approached it. I though it would be very difficult to
>>>>> transfer actual developed and hardened gum image by means of
>>>>> softening it and transferring to the paper. Instead a process
>>>>> similar to a single carbon transfer was appealing to me. Here is
>>>>> what happened.
>>>>>
>>>>> I coated a few sheets of plyester with same emulsion (gum, lamp
>>>>> black, ammonium dichromate) that I used in my previous experiments
>>>>> (expose through the back). This time I exposed in a traditional way
>>>>> from the top. I will call it the gum tissue.
>>>>> This should form a hardened image on top of the gum layer with
>>>>> unexposed and soluble gum on the bottom. We know what happens when
>>>>> you put this image in water. Everything just slides off.
>>>>> OK, I then placed the gum tissue on top of gelatine sized paper,
>>>>> made a sanwich let it sit for a while and placed in warm water to
>>>>> start dissoliving unexposed gum so that the tissue and the support
>>>>> could be separated. Then just wait until the water dissolves the
> >>>> rest of the unexposed gum revealing the image.
>>>>>
>>>>> Some of the difficulties. Even a very short water immersion (cold
>>>>> or warm) of the exposed tissue to remove dichromate softens and
> >>>> starts dissolving the gum, no usable image can be transferred.
>>>>>
>>>>> The tissue image needs to have decent mechanical strength for the
>>>>> transfer. It needs to be thicker, which suggest less pigment,
>>>>> thicker coating.
>>>>>
>>>>> All the air bubbles and imperfection are on top, where the image is
>>>>> formed. There are all visible in the final image. Rollesrs and
>>>>> other means of smooting out the coat do not work with thick layers.
>>>>>
>>>>> My impression is that because the dichromate is present in the
>>>>> transfer process for about 30 minuts, before tissue is pulled away,
>>>>> I am getting a dark reaction, or something, as I am not getting
>>>>> very clean highlights. My exposure might be too long, or dichromate
>>>>> concentration too high as well.
>>>>>
>>>>> My negatives are for Pd printing, not for carbon. Just a minor
>>>>> issue.
>>>>>
>>>>> As Sandy noted I could print in carbon, but it is such a finicky
>>>>> process that requires a very precise time and temparature control..
>>>>> I am still hoping that an easy way of transfer could be found with
>>>>> gum, or perhaps gelatine/gum mix as I am thinking now.
>>>>>
>>>>> I have one picture from this trials and perhaps Katharine would be
>>>>> so kind to add it to her site.
>>>>>
>>>>> Marek, Houston
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>>
>>>
>>
>>
>>
>>
>>
Received on Mon Apr 17 16:11:00 2006