Paper and Ink Stability Testing
This test measures the paper's ability to absorb thinner oils from ink. As the oil leaves the ink film, the ink congeals and eventually dries after a period of time. If the ink contains heavily oxidized oils, it will set very slowly. If the ink is formulated with hydrocarbon oil, it will cure quickly. During this test, we measure the splitting force of ink on paper. This produces a setting curve over time, and the slope of this curve is reported as the rate at which the ink and paper combination "freezes". This test uses a standard "fast cure" cyan ink, but any ink can be used.
"Water" Sensitivity Test
During this test, we apply fountain solution and ink to the paper sample at the same time. This test tells us whether the surface of the paper can accept enough fountain solution to print without snow or bad solids. A densitometer is used to calculate the percent ink transfer in the "water zone" and also records the percent wet coating pick-up (if any) on the sample. This test is especially useful when testing coated papers, as differences in wet pulp can be attributed to drying conditions (amount of binder and degree of cure) or the percentage of starch in the binder system
spot test
We always evaluate the uniformity of ink absorption, as spots in a job can lead to rejects. We run this test with two inks and print them in reverse viscosity order. If the paper absorbs unevenly on the surface, the ink that descends from the first will form an uneven tack and will capture the second ink unevenly. Visually, the spot is rated on a scale from "1" for good to "5" for poor. Spotting on the press depends on the results of this test as well as the P&I Stability and Water Sensitivity tests.
layered
Our delamination test was developed for use on coated recycled paperboard products. This test combines the "bending" effect of the plate passing through the transfer cylinder of the printing press with the surface force of the ink's adhesion-promoting force on the surface. This is passing the test. First, the board is spun in our flexor unit and then placed in the TestPress where a controlled film of ink is printed onto the surface. It prints every 10 seconds and only prints 4 times. Any delamination is considered a failure.
Blister resistance
Solid printing with temperature neutral inks at a controlled ink film thickness of 0.05 mils. Samples were run through a HeatSet Tester, which measures paper surface temperature or printed (web exit temperature). The samples were visually assessed for foaming. Mark endpoints when vesicles occur. This temperature is reported as the highest temperature the paper can reach without blistering.
printing gloss
Gloss can be measured at 20 degrees, 60 degrees or 75 degrees. For print gloss, we use a wet ink film thickness of 0.05 mils. This thickness remained constant during most of our testing. We can also apply gloss paints and flexographic inks. Print gloss can be achieved on thermoset web offset inks and papers, sheetfed inks and papers as well as UV and flexographic printing processes.
