Reference Book
Types of blanket
Blankets may be classified into the following according to their resilience:
Hard blanket, Soft blanket, Medium blanket, Sandwich blanket and Special
blankets.
Hard blanket:- They are having 80° A to 85°A hardness. They are used to
print on matt, rough surfaced, thick coated card and other heavy coated papers.
Soft blanket:- Blankets having 60° A to 65°A are called as soft blankets. Low
grade uncoated papers, polythene sheets and coated papers may be printed
using soft blankets.
Medium blanket:-They are blankets made of 65° A to 70°A hardness. These
blankets are used to print on super calendered or thin coated and glazed papers,
maplitho, thick and thin white paper.
Sandwich blanket:- They are blankets having hardness within 70° A to 80°A.
They are used for printing heavy solid jobs, blankets of 60° to 70° shore hardness
should be used. Fine halftone images need 70° to 80° shore hardness because
they have a better ability to transfer fine screen dots.
Special blankets:- They are special solvent resistant blankets. Vehicles and
solvents of heat-set and quick-set printing inks are not suitable for ordinary
blankets. They require special solvent resistant blankets.
Properties of a blanket
The face of the blanket should have no adhesive properties. The surface should
be sufficiently resilient for better transferance of image on the printing material.
Blankets should have good receptivity to all types of lithographic inks. Blankets
should not become glazed or tacky when its surface comes in contact with
solvents. Blankets should have less affinity for ink than paper so that it may
readily release ink on to the paper surface.
Care and Storage of blanket- Blanketsshould be wrapped round the blanket cylinder properly stretched.
- Thickness of the blanket should be decided in consideration of the bearer
or the pitch circumference. - Blankets should be used with the consideration of the paper surface.
- The unrolled blankets should be laid on plain surface.
- More than one blanket may be placed face to face or back to back.
- Blanket should be prevented from exposure to sunlight, high temperature
and fluorescent light sources.