Why Paper Color Changes

Mark Asked Ralph…

Ralph, can you provide any information on why paper color changes. Same weight same mill and different mills.

Let’s see if I can lay out the basics of hue differences in linerboard.  As you stated, there are certainly differences between mill sites and even within a mill system among machines and over the seasons of the year.

Unless a mill is willing to dye its pulp to provide a uniform hue over time, as in the case of some waste based linerboard producers, one should expect some variations.  The gradations occur because of the location of the trees in the forest, the species, the time of year, the age of the wood chips, the amount of pulping to remove the lignin which holds the fibres together, the amount of pulp washing to remove the cooking chemicals and lignin, and the paper making chemicals.

Please let me know if you need additional details on the above elements. – Ralph

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