Double-Transfer Carbon Printing is a photomechanical printing process invented at the end of the XIXth century. First, an emulsion of gelatin, sugar, pigment and sensitizer is laid on a plastic sheet. This so-called "carbon tissue" is then exposed to UV light under a large format negative.
By developing the carbon tissue in hot water, a relief appears in the gelatin, where the dark and thick areas match the light areas of the negative. This relief image is transferred onto a temporay support. For a colour image, the procedure has to be repeated for the three primary colours (+black). The stacking of the reliefs yield all the colours, similar to watercolour painting. Eventually, the colour image is transferred to a fine art paper.
Originally, separation negatives were produced from a slide. Atelier carbon3 modernizes the process by making it compatible with digital photography. Continuous-tone negatives are produced on sheet film by a high-resolution imager, straight from a digital file.