http://sutlib2.sut.ac.th/sut_contents/H95009/DATA/5636_40.PDF Here is a paper about making a panchromatic dichromated gelatin plate for use in holography. But, anyone who does carbon printing will probably have their curiousity piqued by this statement! The preparation is surprisingly simple (just by looking at it at least), and the sensitizing dyes are Methylene Blue and Rhodamine 6G; easily available on eBay at low prices. Potassium chromate is used, as is TMG. pH is adjusted to 9.18 with TMG or Acetic Acid. THAT'S IT! The holography community speaks of things in a slightly different manner, but the basic mechanisms going on here are the same. Also interesting are pages 7 & 8 which mention two methods to protect a sensitzied-DCG plate from degradation from atmospheric effects. Physical and chemical sealing. Not sure if these would work with carbon per se, but again, intriguing... Lastly, there's a substantial increase in speed. How much?.. I can't say. Pehaps someone versed in milli-joules per centimeter squared can translate this statement, "From Fig. 2, we can find that high diffraction efficiencies can be achieved for all the four used laser lines, and the exposure required to obtain a diffraction efficiency of 80% is about 35 mJ/cm2 for 633nm He-Ne laser, 25 mJ/cm2 for 488nm Ar-ion laser, 25 mJ/cm2 for 442nm He-Cd laser, and 15 mJ/cm2 for 514nm Ar-ion laser, respectively. Such a photosensitivity is significantly higher than other red-sensitive dichromated gelatin or blue-green-sensitive dichromated gelatin."