Scumming

Scumming - Ink adheres to non-image area of the plate during the press run and cannot be removed using a damp sponge.

Causes

Remedies

Ink emulsifying

Running too heavy of an ink film

Lower ink setting. Switch to stronger pigmented ink to achieve desired density with thinner film.

Fountain solution too Alkaline

Increase amount of concentrate, or switch to more acidic solution.

Conductivity is too low

Remix solution.

Plate surface has become sensitized

Use a good plate cleaner / desensitizer.

Too much reducer added to ink

Replace ink.

Fountain solution contains too little gum

Remix solution using more gum, or if using a one-step solution, use more concentrate.

Excessive use of alcohol substitute

Remix solution using less substitute.

Burnishine