What is the TAPPI standard for Warp?

1/4" of warp allowed in a 12 inch span measured anywhere on the sheet.

This information is found in Tappi standard "TIP 0304-13, Statistical process control - procedures for charting warp".

Easiest way to test is to use a 12 inch steel rule and lay it on your sheet, if the gap between the sheet and the rule is less that 1/4" it is typically within Tappi standards.

With todays high speed converting machinery this is no longer an exceptable standard in many manufacturing facilities, especially for high graphics print jobs.