|Wet carbon showing relief image|
Carbon Transfer Printing Using Soot:
A Rough Guide for the Mad
The process starts by mixing soot and gelatine and pouring out into a black sheet called 'tissue'. This tissue is poured onto a carrier paper so that it is easy to handle. Once dry, the gelatine tissue is made light sensitive by applying potassium dichromate and then squashed together with the image negative and exposed to ultraviolet light.
The now 'cooked' tissue is soaked in water and then squeegeed onto a piece of water colour paper (which has been previously coated with a mix of gelatine and formaldehyde) and left to rest for a while. As the sandwich rests, the water moves between the wet paper and carbon tissue and (hopefully) sticks the two together.
The fun bit comes next. The sandwich of papers is then placed in a bath of hot water, whereupon the soot-laden gelatine starts to melt; it is interesting watching the gelatine ooze out of the sandwich
After a few minutes, whilst holding ones breath, the carrier paper is stripped from the sandwich, hopefully leaving the now dissolving carbon tissue stuck firmly to the watercolour paper; this is often where the first volley of expletives get propelled across the kitchen as chunks of the image stick to the carrier sheet and not the other paper.
The image is currently a black mass of dissolving goo. The paper is then floated face down in the hot water for about 15 minutes and hopefully all the gelatine that was under the dense parts of the negative and did not harden with the UV light detach and sink to the bottom of the tray. The next round of expletives is if the image also detaches and sinks!
A dark version of the final image should now be visible. With longer soaking, more and more of the gelatine falls away until the final image is left, ready for drying.
The wet carbon print has a very interesting characteristic; the more UV light hit the gelatine when being exposed, the thicker the layer (and so the more soot) that is left. The result is that a strong relief image is visible in the wet print (as in the image above). Some carbon printers strive to get as thick a relief as possible so that even when the image is dry, there is still some textured relief visible.
With the watercolour paper I use, there is little or no relief left when it is dry; apart from the odd lump of course ground soot that is.
The detailed process is summarised in the sections below; hopefully I have made them 'simple' enough to follow, however each stage requires many attempts and practice before you can make a decent print. You must be mad if you want to try this!
Stage 1. Preparing the pigment
The first part of carbon transfer is to first find a source of pigment. Many folks are sensible enough to squeeze some ready-prepared pigment from a watercolour paint tube; it is very finely ground and intimately mixed with a little gum Arabic as a carrier. The result is that it mixes easily into the gelatine mix and makes fine prints. By mixing various paints, a whole spectrum of colours can be achieved and even multi-layer colour prints can be made.
- It is recycling a waste product (i.e. it is free)
- Soot is made from particles of carbon and therefore will not fade and really is the ultimate in permanence for printing with; unlike some of the water colour pigments which could fade.
- I can control the particle size in the pigment to add extra texture and character to the prints.
- Carbon transfers made with pukka soot are rare these days, although I doubt it will help me sell any!
- It smells of soot
- The soot has tars and other contaminants; many of them are yellow in colour and absorb UV light and stain the paper. The oily compounds can make mixing with the gelatine a right royal pain.
- The tiny particles of carbon are all clumped together into big chunks so it needs grinding.
Method 1: Basic
Method 2: More refined
Stage 2. Making The Glop
|Gelatine, sugar and soap melting|
|Hot glop after soot added|
|Remnants of pigment in filter|
Stage 3. Pouring the tissue
|Marking out tissue support papers|
|Wet tissue support paper squeegeed to board|
|Pouring glop on paper; pour slowly to let glop cool and slow the spreading|
|spreading glop with an *old* comb|
|poured tissue gelling (and attracting dust)|
|set tissues hanging to dry|
Stage 4. Sizing the final support paper
The most reliable surface sizing I have tried is gelatine that has been hardened. Quite a thick coat of gelatine is needed to produce reliable transfers, but with water colour paper, even a heavy coating is not really noticeable as it sinks into the paper. If a really heavy sizing is applied so that the paper surface is shiny, when the carbon print is transferred and dry, the relief image of the raised gelatine may well be visible.
I coat the front surface of the paper twice with the following solution:
I let the gelatine swell in the cold water to start with and after about half an hour, give it a blast in the microwave to get it to about 45 degrees centigrade and all melted. I then apply gloves, apron, goggles and stir in the Formalin and retreat outside, with the wind behind me and a vapour respirator on, to brush the solution onto the paper. The mixture does not have a strong odour (I find that Formalin smells slightly 'sweet'), but would very quickly make your eyes sting if the wind changes direction (good fitting goggles are a must of course). Formalin is nasty stuff but does a fantastic job at hardening the gelatine (and any other tissues it comes in contact with).
After coating, I leave the paper to dry and the smell to subside for a day, then repeat the process with a second coat. 100ml of the solution is enough to generously coat 2 full sheets of paper (22"x30" sheets). After the second coat, the paper should be left hung for a few days to allow the last of the Formaldehyde to out-gas, then the sheets can be cut into the required smaller sizes. If I am short of paper and the sheets have only hung for a day, I will soak them in water to help remove the last traces of Formaldehyde and then dry them before use.
It is critical not to store hardened paper anywhere near sheets of carbon tissue as the last remnants of Formaldehyde gassing out of the sized paper can prematurely harden the tissue.
Stage 5. Sensitising and exposing the tissue
|Tissue being trimmed to size|
|preparations for mixing sensitiser|
|sensitiser ready for application.|
All of the remaining operations are done under dim incandescent light; the tissue is sensitive to daylight and fluorescent lighting and if exposed, the image will be fogged. I often have to help the tissue to be fully dry at the end of drying with a hair dryer (an old one and a respirator face mask!).
|Sensitised tissue ready to be dried in the dark.|
Once fully dry, the tissue can be mated to the negative and exposed to ultra-violet light. There is quite a bit of trial and error up front to work out the strength of the sensitiser and the exposure time needed so often the first few prints are no good :( It is a good idea to place a thin piece of acetate between the negative and the tissue as if the tissue is not fully dry, it will stick to the negative and trash it.
|Negative against the glass of the contact frame|
|Tissue and negative in contact; note the tissue is within the safe-area|
|Exposing with UV light|
Stage 6. Transferring to the support paper
|Final support and tissue soaking in degassed water|
|Lifting the paper and tissue from the water|
The sandwich is now squeegeed onto the board; I use a roller as it allows me to control the alignment of the tissue better. The roller is used to expel water and any trapped air from between the tissue and the support paper. I roll from the centre outwards to push any air out towards the edges.
|Rolling the tissue and final support together.|
|Draining the sandwich|
Stage 7. Developing the image
|Oozing glop from the tissue edges.|
|Final support paper just after removing the tissue backing paper.|
|Part developed print|
Stage 8. Final washing
|Final print after drying.|
|Soot-based carbon transfer test sheet|
|Sun exposed ink-jet image on right, fresh print on left|