Test Procedures

Printing Blanket Test Procedures – Important Notes

Offset Printing Blanket and Rubber Compound Test Procedures require special consideration before entering into a new R&D program.

After gathering the required equipment, starts Test Procedure study and of the required parameters, which values result from the test. Writing the software script follows, containing the instructions that enable to perform the test as specified by the standard. This includes a decision on which markers will be automatically placed during the test’s course or afterwards and pos-test calculations.

Please note that test procedures will often need adjustments to conform with the equipment available at particular laboratories. One example was our need to use two different sets of grips (and procedures) in the elongation and tensile test. ISO 12636 is used as an overall basis for the tests considered above.

Let us, however, take a closer look at the only ISO standard that concentrates on printers blankets specifications and testing.
ISO 12636 text reflects the votes cast by over 75% of ISO Technical Committee TC-130 members, including blanket manufacturers.
It does define Test Procedures that ignore the important presence of the typical Rubber Rebound. It does also ignore the much relevant Anisotropy in Printing Blankets with fabric carcass(*):
– Compression Tests prescribe test procedures with 4.5 compression cycles, not considering the final Decompression Segment. But it is precisely on this segment that a Rubber Rebound takes place, important enough to condition Web printing efficiency.
– Compression Indentation considers a circular Indentation Disk instead of a Rectangular Indenter of equivalent area. The Results afforded by a Circular Indenter are Unsuitable to draw any conclusions related with Directional Properties of printers blankets.

There is an increasing fear of the medium-term negative consequences of the limited knowledge ambition mirrored by the existing standard. The inevitable damage caused to Offset Industry will largely exceed the overall sum of any existing manufacturer’s legitimate interests.

(*) – Sticky-backed blanket operating responses are obviously different.