Cause:

Dirty plate, improperly inked plate, unclean fingers, perspiring fingers

Solutions:

The plate should be cleaned to prevent a build-up of the ink, and particles of lint and dust.

A thin, even coating of ink on the plate is necessary to obtain clear, distinct finger impressions.

The fingers of the person fingerprinted should be clean before fingerprinting.

Excessive perspiration will result in the failure of ink to adhere properly to the tips of the fingers.  Wiping each finger with alcohol or other drying agent before inking and printing will reduce the amount of perspiration.