Brush Sensitizing Carbon Tissue vs. Bath Sensitizing

[AndyDDuncan]

After almost a ten year hiatus, I've decided to start doing carbon transfer prints again. As it's been close to a decade since I've done any carbons, I've been perusing the forum here to refresh my memory on techniques. One thing I've come across is brush sensitizing the tissue. What are the advantages of brush sensitizing over sensitizing in a bath? I can see how conservation of the potassium dichromate can be a plus, as well as not having to deal with wasted/used sensitizer. But what other advantages are there? And how does one go about sensitizing? Will dilutions change? For example, if I'm sensitizing in an 8% bath, if I sensitize with a brush, will I need a different concentration? Also, does the tissue need a pre-soak in a water bath before sensitizing?

Sorry if this has already been covered. So far I'm 20 pages deep into past topics in the Alternative Processes forum, and these questions hit me, so I figured I'd ask while they're fresh on my mind.

Thanks!

 

[Vaughn]

No pre-soak needed for brush sensitizing. There is also a method which uses both (a bath that is used to brush dichromate onto the tissue.)

Any method can work...it just requires consisent methods for repeatibility. I prefer brush as I can deliver the exact amount needed no matter temperature and other factors. Like you said, no waste. Baths cannot be saved for later use, as the introduction of organic matter greatly affects its strength and longevity. You will have to test your tissue with your negs to determine the best dilution. An 8% solution is quite high, but I have standardized on it, as my negatives have tons of contrast. I think the average concentration is closer to 4%.

I use acetone as a carrier for the dichromate...and a bit more than most carbon workers. I find using more acetone allows for a more even distribution of the dichromate. For example: For a tissue for an 8x10 negative, the tissue is 9x11, or 100 sq inches -- I use 5ml of an 8% dichromate solution (in water) mixed with 15ml of acetone. If using alcohol, less is needed as a carrier as it evaporates at a much lower rate...one has more time to move it around the tissue.

Also, at warmer air temperatures (which can cause problems with brushing the pigmented gelatin), I find the acetone cools down the tissue surface significantly as it evaporates.

Good luck in getting re-started!

 

[AndyDDuncan]

Thanks Vaughn! It was actually one of your old posts that made me think of my questions!

Without a pre-soak before brush sensitizing, I take it the gelatin swells enough to allow thorough and even penetration? I remember I poured my gelatin pretty thick–I think it was over 1/8" (3.2mm) thick when wet. I may or may not pour that thick again. I haven't decided, or even thought that far ahead yet. If I do decide to go that thick, will brush sensitizing still work? Or will I need to sensitize in a bath?

Tonight when I get home from work, I'm going to dig into storage and see if I can't find all my old notes. I've got Sandy King's book, and I think a lot of notes are in there, as well as a paper that was handed down to me by my photo teacher back in college that he got from his photo teacher who was a master carbon printer, right on par with Sandy.

 

[Vaughn]

My tissues are thick. I use 1.2 ml of glop per square inch. Overkill, and the next time I pour (working on a new darkroom), I will try 1ml per square inch...then down from there if all is well.
And sorry to all the purists for mixing English and metric measurements!

 

[Andrew O'Neill]

I prefer spirit sensitising (with acetone). Less dichromate is required, and application is quick and easy. When my working room's RH is 50-60, everything works beautifully as far as pouring tissue, setting/drying and sensitising/drying. Temperatures above 24C coupled with high RH just spells disaster. I don't bother. A dehumidifier helps but... the best time for carbon printing up here is winter!
My tissues are about 2mm thick when wet. For the past few months, I've been using a very lightly pigmented glop. 2ml India ink per 750ml glop. I'm getting decent relief. I've also been experimenting with Carbon over Kallitype and am very happy with the results.
Cheers and welcome back to carbon printing!

 

[AndyDDuncan]

Thanks for the input so far!

I've pretty much decided on the spirit sensitizing method. Vaughn, I've read in some past posts that you use a regular cheap-o paintbrush? (Or was it a foam brush?) I've used hake brushes in the past for another photographic process, but I can't remember which one now. It was when I was in college 15 years ago. I know whatever process it was, the metal wire holding the bristles in didn't affect the chemistry. I also know that in some processes that that wire can affect the chemistry. Is potassium dichromate one of chemicals that can react to the metal?

I've got most of my chemicals ordered. And by most, I just mean the dichromate. I forgot about glycerine, and sodium bisulfite. In the past I used matte fixed out photo paper, but I think this time I might try Yupo(?) watercolor paper, since I've been reading good things about that. I did size Rives BFK back in the day, but it was textured enough that the relief I love to see in a carbon print was lost.

 

[Andrew O'Neill]

I use a foam brush. Get the high density ones from a paint/hardware store. DON'T get the ones from the dollar store!
I've never used glycerine and never needed sodium bisulfite. I acrylic size my papers, so there is no dichromate staining. If you're going to use Yupo, you won't have to worry about that either as it's a synthetic material. Just make sure you clean it really well with soap as it may have a layer of grease or something on it.

 

[Vaughn]

I use Purdy brushes from the hardware store -- not the cheapest brand, but not too expensive. I have not worried about the metal -- usually does not get the chemicals on them since one uses so little. I rinse well with water afterwards and pre-wet the brush with distilled water before use. (out of habit -- may not be needed).

Glycerine is only useful if one works in very low relative humidity situations -- otherwise it causes all sorts of drying problems.

I use fixed out photo paper -- glossy.

 

[AndyDDuncan]

Does Yupo have any issues with curling when used for the tissue? I've used bristol board before, and when the tissue dried, I would have to pin it to a piece of cardboard in order for it to dry flat. Will I have to do the same with Yupo?

 

[AndyDDuncan]

I just remembered I've got a ton of 20x24 film that's about 20 years old that I use for lumen prints. Could I fix out a couple sheets and use it for the tissue? Does that material have to be opaque? Or would the film that is transparent work?

 

[Vaughn]

I use to use litho film that students made images on then tossed away. Some mighty strange images at times. No problem. It was 0.004" thick and easy to use -- and reused for 20+ tissues.

I use fixed-out x-ray film now (14x17). As it is 0.007" thick, I give it a little more safe-edge (inch instead of 0.5 inch) just to make the handling easier.

I use a black backing board to reduce any chance of UV light reflecting back into the tissue from behind.

As for your previous question -- Yupo should be no problem, but the thicker one pours, the more curling one seems to get.

 

[Andrew O'Neill]

I prefer to use the thinner stock of Yupo for tissue support. It's easier to peel away in the development bath. The thicker stuff is too stiff for my liking. Yes, the thinner stuff curls but I put in quite a bit of sugar so that reduces it quite a bit.

 

[Vaughn]

The last tissue I used was poured thinner (by half, maybe) than my tissue...and was on the thinner Yupo. Stored rolled up -- I was surprised how easy it was to roll out and tack to cardboard for brush-sensitizing.