When one "job" mixes multiple substrates or finishes without a clear reason, you get color and feel differences between pieces. Consistency requires the same material and finish across the run.
Why mixing causes problems
The same file on different papers or different laminates can look different. If you order "500 brochures" and half are on one stock and half on another, the two stacks will not match. Binding or finishing can also be affected.
When mixing is intentional
Sometimes different pieces in a kit are deliberately on different substrates (e.g. insert vs cover). That is a design choice. The mistake is mixing by accident—e.g. reordering on a different stock without specifying.
To keep consistency
• Specify one substrate and one finish for the whole run unless you have a reason to vary.
• On reorders, confirm we use the same material as the first run.
• If you must mix, document it and ensure the printer knows which piece gets which material.
Common mistake
Reordering and accepting "equivalent" stock without checking. Equivalent is not identical. Color and finish can shift. Specify the exact product or accept visible difference.