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Monday, March 24, 2014

Paper Machine Control Strategies: Color Matching (Part 2)

There are predominantly two approaches to color control in the Paper Industry.

The second approach is to control color separately and fluorescence simultaneously.  This method includes ultraviolet (UV) light from the light source for controlling color as well as fluorescence.  This mingling of the affects of optical brighteners with the affects of the dyes is then used to match the standard.Pros and cons:

When pulp brightness is especially good or other variables help increase the sheet brightness, less optical brighteners can be used and this helps lower costs.

This method leads to metamerism even from the same machine in the same mill, as different optical brightener levels lead to a very different looking sheet under different lighting conditions.  The control strategy is also more complex - with a three-dye system there are 13 variables to control.

Control variables for Grade 1 using the UV included measurements
to control Color and Fluorescence

Dye 1
Dye 2
Dye 3
variable 1
variable 2
variable 3
variable 4
variable 5
variable 6
variable 7
variable 8
variable 9
variable 10
variable 11
variable 12
Fluorescent component

variable 13

Part 1 of this discussion on approaches to control color in the Paper Industry revolves around controlling color and fluorescence separately.

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