Lith Printing

Booklet Printing and chemicals involved

In addition to the use of chemicals in the fountain solution the pressman will often use an acid based solution called 'plate etch' for cleaning the non-image parts of the plate. Plate etch is necessary for removing ink which has become attached to the non-image areas of the plate. Its action is designed to make the plate surface clean and to give the desensitising properties of the Gum Arabic its full effect.

1. The plate is gummed up and thoroughly dried.
2. Image ink in the deletion area is washed off.
3. The surrounding area should be protected by masking with a
waterproof tape.
4. Deletion fluid is applied with a brush and left for the prescribed period
(usually 30 seconds).
5. The deletion fluid is washed off with water and the tape is removed.
6. At this point production may continue although full
desensitisation of the deleted area will be achieved if the plate is gummed up and dried before use.

Inking in ready for a bit of flyer printing

Traditionally the plate image was inked with black ink after processing. This improved image visibility to aid job identification, increased the oleophilic qualities of the image and protected it from the desensitising action of Gum Arabic.


The modern presensitised plate does not require inking-in to improve its ink receptivity. Platemakers however do use inking-in solution on the processed plate to assist in job identification, and in many cases inking-in may be required to protect the image from desensitisation by gum.

Positive-working plates may be susceptible to breakdown if exposed to light over a prolonged period of time. Inking-in solution is therefore applied to this type of plate by the platemaker and also by the pressman after the job has been printed to prepare it for storage.

Inking-in solution is applied to the image in the following manner. 1. The plate surface is washed with water. 2. A small quantity of inking-in solution is put on a soft cloth or pad of cotton wool which has been damped with water. 3. Light rubbing of the image with the ink will now ink-in the image.

Wet washout

This is a technique used by the pressman to prepare the plate for immediate printing. Wet washout is usually applied when the plate is on the cylinder and should be performed rapidly.

1 . The plate gum is washed off with water. The entire plate must be wetted.
2. A cloth impregnated with white spirit or washout solution is rubbed over the
image to remove the inking-in solution. The plate must not be allowed to dry.
3. The entire surface of the plate is finally washed with water before starting the press and applying the dampers.

The problem for flyer printing is the same for leaflet printing and all types of full colour litho print

The fluid contains a strong chemical which effectively removes the unwanted portion and desensitises the plate surface as well. The best deletion fluids do not damage the plate grain.

A deletion fluid should be of tacky consistency so that when it is used on the press it does not flow down onto other parts of the plate.

The fluid is usually applied with a brush onto the deletion area which has been cleaned from ink. For application to areas surrounded by other images the following procedure should be adopted by the printer:

Graintess plates give high image definition but have the disadvantage of being