Separation Anxiety - Carbon not letting go..

[sly]

I'm new to carbon printing. Took workshop with Vaughn 10 days ago and am now playing with the tissues I brought home.

I'm having trouble separating the film and tissue from the fixed out RC paper. After exposure (with a cardstock matt over glass for unexposed edge), I'm mating them in cold water (50C). Out of the water in 20-30 seconds, squeegee'd, dried with shamwow cloth, pressed under glass. Tonight, after getting 5 under glass, I paused for dinner.
After dinner, hot water (110-120C). Soaked for 3 minutes before trying to separate - gelatin was seeping nicely from the edges. The first 3 prints a section of the glop completely separated from the film. After another 5 minutes in the hot water half the image was visible, the other half obscured under thick blackness. Giving it more time and pouring warm water on that section eventually dissolved the excess, and the prints look OK.
The last 2 prints the glop stuck to the film, and a portion of the image stayed there, leaving a blank, white patch on the paper. Not salvagable, obviously.
I brush sensitized between 1 and 2 PM. Developed film for an hour and a bit while they were drying. Exposures, squeegeeing, and pressing were all done before 5. Dinner break, back to work before 6. Processed in same order as went under the glass (so all were under glass for at least 30 minutes.) Done around 7:30.
One thing I'm not doing as taught - I'm not using 16x20 glass to press my 4x5's. I just don't have the counter space beside the 16x20 sheet I'm squeegeeing on. I'm using 8x10 glass with a weight on top - a full 2 liter bottle. Could that be the problem? Too much weight? Not enough?
Any insight gratefully appreciated.

[paul_c5x4]

I usually put a 5Kg(ish) weight on top of the mated sandwich. After an hour or two, it goes in to the hot water bath and I keep slopping the water around until the tissue separates on it's own accord. It usually takes ten to fifteen minutes before this happens.

[holmburgers]

Are you using a safe edge?

I've had nothing but problems with this as well, always from fixed out RC paper. I haven't given carbon a very serious attempt yet, so it's hard for me to say with much confidence (it's always been as an aside to something else I've been focusing on), but I wonder if fixed out RC paper doesn't cause some kind of problem. Perhaps the hardeners in the fixer are insolubizing the tissue?

IDK, just a thought.

[artonpaper]

I have a little carbon experience. I don't like RC paper for anything, so when everyone said to try it, I didn't. I used Bostick and Sullivan tissue. I do not put weight of any kind on it. I just adhere it, waited 20 minutes and soaked it in warm water, 100ºF. Sometimes the prints take a longtime to let go. Up to 15 minutes to just begin separating. Three minutes is too soon. I give the smallest tug, and if there's any resistance, I wait longer. I almost always get good results when adhering to YUPO or to uncoated baryta paper. I've also made a few good prints on COT-320 sized with hardened gelatin. You can see a few of my carbon prints in my gallery here at APUG .

I assume you know about the Advanced Process and Carbon Board.

http://bostick-sullivan.invisionzone.com/

[Hexavalent]

20-30 seconds seems like a short soak time to me.
I usually soak the tissue for 1.5 minutes, slip RC paper into the water just to get it wet and pull the sandwich out within a few seconds. Of couse, as is the way with carbon transfer, your glop formula, sensitizer, exposure, support, water temperature and the phase of the moon are all significant variables. In my experience, a slight, but EVEN pressure is all that is needed - large amounts of pressure don't accomplish much except increase the risk of marks. My 2 cents CDN.

Cheers!

[Andrew O'Neill]

The last 2 prints the glop stuck to the film, and a portion of the image stayed there, leaving a blank, white patch on the paper. Not salvagable, obviously.

What's your water like in Nanaimo? Have you tried cold, dead water for the transfer? I put a bit of vinegar in the transfer bath to make it slightly acidic and that seems to help. My water is a bit alkaline.
If you are going to stick with RC paper, use a non-hardening fix, such as Ilford's rapid fix and wash paper thoroughly. I soak my tissue longer than most people. 2.5 minutes. The RC substrate is stuck in, mated and pulled immediately, squeegeed, wiped with sponge, and left under heavy glass. I always place a 4L milk jug (containing water) so that glass is pressing down firmly.

[gmikol]

I would think you might have to soak the tissue longer in water before mating.. I soak my tissues up to 2 minutes in 55-60F water prior to mating with RC or FB photo paper. They're thick, like Vaughn makes, but I use glycerin instead of sugar (and it tends to be a little drier where I am compared to a coastal location.

The gelatin has to absorb enough water that it melts readily in the hot water development, and not so much that it interferes with the mating. Try extending the soaking time before mating before you change any other variables and see where it gets you.

Good luck--

Greg

[sly]

Ok, I have a few variables to play with - vinegar in the transfer water (my well water is alkaline) and a longer soak in the transfer bath before mating. Vaughn had suggested that the soak, mating, and squeegeeing should all happen in a minute. I've been letting the water sit (so it's dead) before using. I'd already decided to leave a wider safe edge. Also a longer soak in the hot water before trying to separate.
Now all I need is more darkroom time.

[Jim Fitzgerald]

The joy of carbon is figuring out your work flow. Good luck.

[John Jarosz]

I'll assume you made some good prints at the workshop. That is your starting point.

Any change can have a good or bad effect (but usually bad). 99.9% of the population that makes Carbon transfer prints does not know all the cause/effect relationships that exist. Further, Carbon is not a process that you can make changes to by rationalizing or using logic to be able to say that your change will not have an effect.

Go back to the process exactly as you learned it and get some good prints. That is your starting point. Then you can change process parameters ONE AT A TIME to see if your new process will work.

Different water can have an effect, so can humidity, temperature, drying time, phase of the moon (oh, someone already said that ), type of support, transfer time, soak time.

You're in a relatively easy position because you've made good prints before - so you know how to do it.

John