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Reworking the Rainbow

(March 1999) posted on Mon Dec 13, 1999

Learn about the issues in color control and proofing that printers face when producing ceramic decals with process-color separations.

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By Jere Williams

Once a proof is accepted, it can be closely replicated on press during the production run. Since most conventional printers run all of their colors at once, and since the printed color is also the final color, the accuracy of the press prints relative to the proof can be quickly verified as the first production sheets are completed.

Unfortunately, ceramic printing has yet to benefit from similar technology. Although technically feasible, no proofing system currently available will accurately represent fired ceramic colors. Thus, ceramic printers must rely either on their computer monitors or on conventional contract proofs with non-ceramic colors. With this latter option, color fidelity depends on the accuracy of the translation from ceramic to conventional color space and is subject to all the same translation problems described previously.

Due to the lack of a reliable, standardized contract-proofing system for ceramics, the ceramic proofing workflow is much more laborious than its conventional counterpart. Typically, clients will provide original art, a transparency, or a conventional contract proof as a color target. The ceramic printer then must translate the incoming color into the ceramic color space best suited to the project, using the color displayed on a computer monitor to verify separation accuracy. Film is then output, screens are made, and the job is sent to press.

Next, the press operator will print the work, focusing primarily on controlling dot gain. Since colors on the final print bear little resemblance to the colors that will develop with firing, assessing the printed but unfired decoration is unlikely to uncover color fidelity problems. Color assessment must wait several hours for the decoration and firing to be completed. Then, if color problems are detected, the entire process must be adjusted and repeated--from prepress through production.

Firing concerns

Correct firing parameters are also critical in maintaining color fidelity. In order for the printed pigments to attain their final colors, they must mature at a given temperature. Any variation from the desired temperature and atmosphere of the kiln can alter the color that develops during the firing process.


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