HP Indigo Troubleshooting – Gap Deletions

Q. How do I improve the print transfer into the recessed gap of the FlexBind® page?

A. The heavier the FlexBind®base paper, the more significant the recessed gap will be and the more difficult it will be to adequately transfer ink without causing a “gap deletion”.  Refer to the suggestions below for some alternatives.


Gap Deletions are described as printing voids that occur in the recessed gap of the FlexBind® hinge.

  • It is not recommended to print through the gap.  Printing should be registered to the edge of the gap, or slightly into the gap to a maximum of 1 mm.
  • Printing into the gap on thicker substrates is problematic because the variance between the recessed film gap (hinge) and the outer surface of the paper is so great.  Thinner sheets up to 200 gsm typically print well through the gap without any modifications to the press.
  • Printing for long durations with excessive gap deletions can cause ink build-up on the blanket which can transfer to the ITM and damage equipment.

While it is not recommended to print through the gap, some printers have found some success using a combination the the tips below.

  1. Run extra cleaner sheets to avoid ink build-up on the blanket
  2. Decrease the blanket temperature to 150 deg C when the blanket is new to improve ink transfer.  A worn blanket often has better ink transfer than a new blanket.
  3. Be sure to recalibrate the first and second transfer calibration when changing the temperature of the blanket.
  4. For the 5500 and lower presses, run the substrate on “Uncoated, Matte”
  5. Increase the force between the blanket and the impression cylinder.  This is done under the Advanced tab under “Substrate Settings”.  100 KG is the standard force setting which can be varied +/- 30 KG.  (Once the force setting is changed, it will NOT go back to the default setting once the press is rebooted.  It should be manually changed back if desired.)
  6. The 7000/7500 press has a higher force when printing and typically has better print capability through the recessed gap.

The final option for eliminating the gap deletion is to avoid printing through the gap.  To eliminate the appearance of the white gutter at the center of the book, which tends to be viewed as a void, the gap is preprinted with a black stripe.  The black gutter area is more aesthetically pleasing than the white gutter.

 Gap Deletion