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Dave Miller
08-12-2007, 01:27 AM
Akki14, it seems you should consider using fibre base paper,single weight if you can get it.

Loris Medici
08-14-2007, 05:11 AM
I tried with cyanotype paper today and the results weren't so sharp. It's probably because cyanotype works based on shadows more than on anything as fast as silver gelatin paper which reacts to any light not just mostly-UV light. I use a proper contact printing frame so I'm definitely getting good contact between paper and paper.

Hi Akki14.

During the long exposure, have you moved the frame from time to time - in order to maintain the angle of incidence? Sun will take a long way in the sky in 2-3 hours, changing the angle of incidence considerably and giving you an effect similar to motion blur.

Regards,
Loris.

Akki14
08-14-2007, 09:51 AM
No, I never thought that'd be necessary as I've never needed to do that before and I would have thought the negative is in such close contact with the paper that it wouldn't matter that greatly (or as greatly as I'm seeing). Maybe I'll try a very long exposure with the facial tanner to see if that's the problem.

Neil Miller
08-16-2007, 07:06 PM
Hi Akki,

Peter Frederick, who invented the temperaprint process, has used peeled RC negs to good effect. I read the method he used quite some time ago, so I might be forgiven for some errors! The method was something along the following lines:

1. "Bruise" an unimportant corner of the negative - eg, hit it with a blunt object! The object is to stress the corner, possibly partly delaminating it, but not breaking the surface.

2. Put it in a tray of nearly boiling water. The bruised edge starts to get water-logged first.

3. begin peeling at the bruised edge. If you feel resistance, let it soak a bit longer. You can top-up with hot water as you go to maintain the temperature.

4. When the plastic layer has been peeled from the paper backing, it usually still has bits of paper stuck to it. Let it soak until paper is easily rubbed off.

5. Rinse and dry.

I haven't used the method, so can't vouch for it being simple or quick. I have read elsewhere of people rolling the plastic layer around a pencil or rod to make the peeling easier.

I recall that unpeeled RC paper was used too, but because it is not a simple sandwich (it has - maybe - 4 layers, one of which is a baryta layer for whiteness and opacity) it is very slow, as you found out. I don't think waxing or oiling helped much because of the baryta layer (could be wrong) and sometimes it had side results like making the paper structure/grain more visible, depending on the medium used.

Good luck,
Neil.

Neil Miller
08-16-2007, 07:18 PM
Just a quick thought about the blurring - maybe during the 3 hour exposure the paper expanded due to heat? I expect the contact frame would have to be super-tight to prevent such thermal expansion over such a long time.

Regards,
Neil.

Loris Medici
08-21-2007, 06:35 AM
I don't think paper expansion is the cause here, because the base material of RC papers is very stable dimensionally...


Just a quick thought about the blurring - maybe during the 3 hour exposure the paper expanded due to heat? I expect the contact frame would have to be super-tight to prevent such thermal expansion over such a long time.

Regards,
Neil.

z-man
08-21-2007, 03:28 PM
1. the exp time of 2-3 hours is much to long as is the stated time for the tanning unit--the "cyanotype" material may be the problem-sounds like the senitised solution is deep in the support and/or not formulated properly-i allways start all my experiments with commercial "blueprint paper" material as it is so consistant and will get me into the ballpark fast

2. a single wt fiber base paper can easily be made transparent with "torch fuel"-this is liquid parafin that usually has citronella in it and has been descented --you could use regular kerosine but the fumes will be harsh--baby oil is ok but much too oily

3. resin ctd 'paper' is not paper-the reason for using it as a neg is that there is no fiber grain that will intrude into the print--HOW-EVER- the brighteners that are put into it flouresce very strongly under uv, and it may be that with such long exposures the very bright glow of the support(this would be visable under uv only ) is causing the 'bluring'

4. with so many variables it is very difficult to know what the actual problem is untill some kind of known constant is in the equation--blueprint paper and the tanning unit would be a easy way to test as both are constants

vaya con dios

Neil Miller
08-22-2007, 10:29 AM
Loris - the RC negative is on top of the coated paper....

Regards,
Neil.

Neil Miller
08-22-2007, 10:55 AM
3. resin ctd 'paper' is not paper-the reason for using it as a neg is that there is no fiber grain that will intrude into the print--HOW-EVER- the brighteners that are put into it flouresce very strongly under uv, and it may be that with such long exposures the very bright glow of the support(this would be visable under uv only ) is causing the 'bluring'

Are you sure, z-man?

Kentmere describe VC Select as "...The paper is 190 g/mē coated on both sides with 40 g/mē of polyethylene..."

Forte describes its RC range as "...Fortespeed is graded, resin coated (RC), black and white enlarging paper with a neutral
black image tone. Fortespeed papers are manufactured on a medium weight (175 g/m2)
paper base..."

Ilford, Kodak and Agfa spec sheets that I've read all say much the same - that RC is paper that is Resin Coated on both sides, plus other layers, like emulsion, etc.

Sounds like a lot of paper in 190 g/sm to me!

Regards,
Neil.

Loris Medici
08-22-2007, 11:29 AM
Hi Neil,

I see what you mean - I took it the other way. Thanks for the clarification.

BTW, on my first assertion, I assumed Akki14 dried the coated paper thoroughly, to the point of being "bone dry". This is the usual procedure for many Cyanotype practitioners, because the speed and contrast of the emulsion is very sensitive to humidity changes. This, combined with the fact that it's hard to judge correct exposure from the printout (especially when it comes to delicate highlight tones) one will conclude that it's best to standardize / lock the parameters that way. (Using "bone dry" paper that is.)

Bone dry paper will not expand with heat, what causes the paper to expand is absorption of humidity from air, and heat from sun won't allow the paper to absorb enough humidity from the air to end up being expanded. Instead, humid paper will shrink when exposing under sun. (Bone dry paper won't change dimensions in those conditions.)

Regards,
Loris.


Loris - the RC negative is on top of the coated paper....

Regards,
Neil.

Neil Miller
08-22-2007, 11:41 AM
Hi Loris,

Perhaps there are a lot of other tiny factors involved in this particular issue (blurring):

maybe the paper is not bone dry,
maybe the glass is thermally expanding and taking the neg with it,
maybe the wooden back is expanding and taking the paper with it,
maybe the different coefficients of the various materials used in the frame are warping it over the extended printing period and allowing less than perfect pressure?
Maybe there was just a smudge on the glass?

Who knows for sure? It's interesting trying to reason it out, though!

Regards,
neil.

Philippe-Georges
08-22-2007, 11:52 AM
Ray;

He is talking about unpeeled papers which requires that the wax penetrate 2 layers of poly ethylene. This might not work. I have been told it would not.

If stripped, then it might penetrate to some extent.

I would agree that baby oil might be better than wax. It works on FB, but don't forget that PE is quite resistant to penetration even by baby oil.

PE

Dear PE,

Perhaps a very thumb question, but can the back plastic layer or RC paper be 'removed' wit an solvent like acetone?

Philippe