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Carbro Printing

by Richard McCowan

I am the only commercial Carbro Printer in the world. Before I share my experiences how to make the Carbro print, I would like you to enjoy a piece of an article by T.S. Baldwin written in 1903.

It is very doubtful whether any process so completely like the requirements of the artistic photographer as does the carbon process. Its long scale, its deepest shadows combine to render it the most perfect of photographic printing methods. Carbon printing as we know it today is based on the fact that a mixture of gelatin with as chromic salt is gradually hardened and rendered insoluble on exposure to light or chemistry. If, therefore, paper is coated with such a mixture of sensitized gelatin, containing any permanent pigment – carbon was originally used – and if this paper is placed underneath a negative and exposed to actinic light, we shall have a positive image formed consisting of soluble and insoluble gelatin; insoluble in exact proportion as the light has reached the surface of the pigment compound. Development consists in washing away with hot water those portions of gelatin which the light has not affected sufficiently to render insoluble. I would urge every serious photographer to master this fascinating process, for till he has done so, he must be unaware of many of the possibilities of his art.

Now you can understand why I spent two years in the darkroom and tested rolls and rolls photo paper to finally master the Carbro printing know how. What I am going to tell you will definitely reduce your frustration and increase your satisfaction. I already solved the biggest the mystery of how to apply today’s chemical material into the 150 years old formula.

Carbro printing is basically a transfer process. Since there is none transfer paper exists, you have to hand coat you own paper and mix your own chemistry. Besides you can print black and white pictures.

I have chosen Carbro prints over carbon print for the reason that, to make a carbon print, you have to make a negative the same size as the print you would like to have; while a carbro print you can enlarge the image from a negative to make a silver black and white print the size you want the finished Carbro print to be. You want a sixteen by twenty; enlarge and print a sixteen by twenty print. Small trick, always leave at least a half inch clean border around the print. This is called a safe edge and a must for Carbro print. Since I am working with a bromide print I have the advantage of being able to dodge, burn, and change the contrast as I like. I prefer the freedom and voluntarily migrate from Carbon to Carbro. Carbro combines two words, carbon and bromide.

To make a silver gelatin print for Carbro process; I prefer using a double weight glossy surface photo paper that has the highest silver content available, the silver in the paper will harden the gelatin in proportion of light to dark, no silver, and no print. I let the print to develop for four minutes to get the most tone out of the paper, I use distilled water to mix the developer and everything else except the final wash in regular water for one hour. You need to make the silver print about one stop darker then normal.

Here is the challenge part to make your own sheets of pigment tissue. The good thing about coating your own is that you can choose the color and the contrast of the pigment tissue. The old instruction books tell you to pour a sheet of gelatin and pigment, let it dry and hold it up to the light, if you can't see the light, its good.

I use liquid carbon as a pigment. It is actually printer’s ink and the pigment size is about five microns dispersed in water. I mix the pigment with the gelatin in cold water and let it set overnight in the fridge to swell. Imaging how many times I sworn the god which did not give me a crystal ball to understand and redo the old formulas. I tried all the formulas that I could find; none came out with great result. I consulted with all the chemistry experts and tested their comment. One conclusion convinced me times have changed and so has the quality of the chemistry and the gelatin. In the late eighteen hundreds when this process was in vogue, you had to let the gelatin set overnight, heat it to a liquid, let it set and get cold again, then cut off the bottom inch to get rid of the unwanted bone and hair. Today the photo gel that you can buy from Kodak or others is cleaner than the gelatin you buy in the grocery store for cooking. Screw the old process; I worked with market available material to accommodate the old formula.

My steps to make a Carbro Print:

  1. Measuring pigment, glycerin and gelatin in proportion and mix with cold water. I just use a kitchen blender to do the mix and works well.
  2. Put the container with mixed materials in the refrigerator and let it swell over night. Stainless steel bowls works great.
  3. Double boiler method to heat and dissolve gelatin at a temperature of 120 f with plastic wrap over the top to keep the heat in, and keep the bacteria and other matter out. Stir constantly to reduce the bubble and air.
  4. After the gelatin cools off, strain the gel with a very fine strainer
  5. Put double weight silver paper in fixer, wash and dry. Before coating, I will presoak this paper again in warm water of 110 f
  6. I use a twenty by thirty sheet of glass set on a frame that I can level the glass and keep the gelatin in place. I will heat the glass with hot water by just spraying it over the top of the glass. Take the presoaked receiver sheet (the fixed out and washed photo paper) from the warm water, lay it on the warm glass and get rid of all the excess water with a rubber squeeze. I use 450ml graduates to contain the warm gel and to pour the gel on the paper. Starting a stream close to the edge and spiraling toward the center, then I put the gel back in the warm water to stay warm and spread the gel with my fingers till it al comes together in a solid sheet. If you don't lift your fingers when coating, you don't get bubbles.
  7. Now let the gel cool, I use a fan in the darkroom or run cold water under the glass, when it’s solid, hang it up to dry and the next day you can start to work. It takes about 50 ml to coat an 11x14 sheet.
  8. The silver gelatin print needs to presoak for about fifteen minutes in cool water lay it on the glass sheet, removing all excess water, using the rubber squeeze and even a paper towel if necessary.
  9. Soak the gelatin coated sheet in the sensitizer for about three minutes at 68 degrees f or until it lie flat, a lot will depend on the humidity of the air where you are working.
  10. On a 100% leveled surface, lay the silver print at the bottom and face up. Remove the sensitized sheet from the chemical bath and drain well, face down. Put the two together and make sure they have a good contact. If they slip when bringing them into contact, you will get a blurred image. It’s a good idea to have registration pins place in the board or sheet you are working on and hole to match on both the tissue and the print you are using. I then place old newspapers over the sandwich and a sheet of glass on top of that for weight to be sure the contact is good. Let it set for 20 minutes.
  11. Removing the glass, newspaper register and finally the gel and print paper. Taking the gel and print paper apart, lay the gel paper face down on a fixed silver photo paper and registered for another 20 minutes. The image from the receiving paper will be transferred to the fixed double weight silver paper. The paper with silver, the gel hardens while the area without silver, gel washed away.
  12. Put them in a warm water of 110 f and let them separate. It will take 5 to 10 minutes to come apart.
  13. Discard the gel-receiving sheet, now you agate softly the fixed paper with transferred Carbro image in the warm water till the unhardened gel washed away.
  14. Hanging up and let it dry totally.
  15. Mix glycerin in cold water, and soak the Carbro imaged paper for a hour which will saturate the pigment and flatten the print.
  16. Dry the print again.
  17. Wala, you are lucky to achieve a perfect Carbro print.

Ansel Adams used to keep a small microwave in his darkroom to dry the test strips quickly, also great for warming up the coffee or taking the chill off the brandy.

Carbro is not a sixty minute photo process, it takes about three days to make a print, one or a dozen.It’s the drying time that eats up the clock. Please visit my website: www.carbromac.com for more information.


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