The master standard should always be established from one "originating" mill and one "originating" machine at that mill. If at all possible, this machine should be the machine that produces the largest percentage of this grade for the market. Once the master standard has been established, a large sample should be sent to all the mills for establishing their master file, master sample and reference sample (this will be covered in a future post).
|Black bag and master samples|
When replacement of the master standard becomes necessary, the new master standard should come from the same mill and the same machine. This master standard must be a good non-metameric match (reference Metamerism posts). If major changes occur to the machine e.g. a top wire former is added, a new master standard may need to be established as soon as the changes on the machine have been stabilized.
Also, if any major changes in the mix of species (HW, SW, recycled) is made, a new master standard must be established. Finally, if any change is made to the dye being used (supplier, type, mix) a new master standard will most likely need to be established.
For more information on practical aspects of paper color matching, contact me at firstname.lastname@example.org.