Synthetic rubber is used in roller creation: a complex mixture of organic

rubber and several chemicals that obtain their strength and

resiliency through the vulcanization procedure. It is the raw rubber that

adds the rubbery material its necessary qualities. The vulcanization

agents are added to this for the upcoming vulcanization process.

Plasticizers (liquid oils) play a major role as they – in addition to the extenders

and the vulcanization agents – determine the upcoming degree of hardness

of the material. The more plasticizers are added, the softer the rubber after

the vulcanization method.

Shore Hardness

The Shore hardness of a roller identified with a Shore meter

designates the resistance towards penetration of a needle using the

form of either a conic section (Shore A) or a point (Shore D),

pressed with a defined force (1 kp) for a period of three seconds

on the rubber surface. Soft rollers are measured with Shore A,

and hard rollers with Shore D. Inking rollers are required to be adjusted

to be oil-friendly (or oleophilic). In an inking system having conventional inks,

rollers of Shore A hardness in between 30 and 35 are used.

For UV inks, rollers with Shore A hardness of 25 and between 40 and 45 are used.

• Dampening rollers should be water-friendly (hydrophilic). For alcohol

dampening systems, Shore A hardness of between 25 and 30 is suitable.

In direct dampening systems, hard rubber rollers are employed.

Roller Protection

For washing the rollers it is recommended:

1. Use a water miscible wash to get rid of the top layer of solvent-soluble and water-soluble particles that came from the nap of the roller.

2. Apply a non-grit roller paste to take out the insoluble particles.

3. In the end, wash a second time with a water-miscible wash to eliminate the remaining soluble particles.

Glazing

Over time, rollers pick up particles from the ink, the paper coating and the

dampening agent which block their pores. This contamination ends in a

smooth shiny surface. Inappropriate detergents and hard water contribute

to this effect. Transport of ink and dampening solution is noticeably inhibited

because of this.

Problems with irregular rollers

-A worn out roller, a roller with damaged bearings, rollers set with too much pressure or, a roller that has not been adequately cleaned, can cause:

* color inconsistency

* poor solids, or mottling

* streaks

* muddy print

* extreme dot gain

Apart from the obvious expenses of poor print quality, as well as wasted paper and ink, bad or improperly maintained rollers could cause excessive press downtime, raised running costs, and shorter roller life.

Storing of rollers

If possible, do not expose rollers to direct natural or artificial light.

• The special paper that the rollers come served in prevents light

entering

and therefore helps keep the rubber’s qualities.

Because of this, do not remove the paper before applying the roller in the

printing press.

• Always enter the roller with its pivots on a structure support: Installing it

down right onto the rubber can result in permanent deformations

(pressure marks).

• Keep rubber rollers in a cool and dry place.

• Within specific situations ozone leads to microscopic scratches on

the rubber surface. Due to this don't store rollers closer to

motors or other electrical gadgets.