Natural colorant extracts from norbixin, curcumin, and copper chlorophyll were studied for their potential as paper dyes. Higher consistencies in stock preparation and higher levels of refining were found to favor the retention of these three natural colorants, as evaluated by the sat-uration of the color. For both norbixin and curcumin, color saturation was higher in the acidic range of pH than in the alkaline range. The copper chlorophyllin exhibited a higher color saturation at pH 6.0, with values falling below pH 5.0 and above pH 7.0. Generally, aluminum sulfate and cationic starch contributed to the retention of the natural colorants. The addition of precipitated calcium car-bonate fillers reduced the color saturation of the three colorants as a result of the tendency of the PCC fillers to mask the color of the papers.
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