Inkometer Tack ASTM D4361:
Inkometer tack is measured at 800, 1200, or 2000 rpms using the ASTM method. The batch-to-batch tolerance should be plus or minus one point at I minute. There should be at least 1.5 gram-meter drop in tack between the cyan, magenta and yellow. Tack should not increase more than 2.0 gram-meters per minute for stability.
Printing Tack, (P&I on Acetate):
This non-absorbent substrate gives us data that simulates the tack of the ink at a film thickness that is closer to the printed film on press. We estimate this film thickness to be 30 times thinner than the amount of ink used on the Inkometer. And, we also believe that this data is a combination of “tack” and “viscosity” We can also measure the set rate of inks by using our standard paper as a control. The batch-to-batch tolerance should be + or – 25 points. There should also be adequate tack separation between the cyan, magenta, and yellow. Good tack separation is defined by 25-50 difference between the inks, starting with the cyan being the highest and descending from there.
Printing Tack (Set Rate):
This test measures the ability of a paper to absorb the thin oils from ink and the set rate of ink on our standard paper or any other paper. As the oils leave the ink film, the ink sets and after time, eventually dries. If the ink contains heavy oxidation-type oils, it sets slowly. If the ink is formulated with hydrocarbon oils, it will be fast setting. During this test, we measure the splitting forces of the ink on the paper. Over time, this generates a setting curve, and the slope of this curve is reported as the rate at which the ink and paper combination “set”. A standard “Fast Set” cyan ink or standard coated paper is used for this test, but any ink can be used.
Solid Prints/Side-by-Side comparisons of Batches:
The wet ink film thickness we use for is measured at 0.05 mils. This thickness remains constant throughout most of our test procedures. Using this procedure, a single print can show differences in strength and hue between batches of ink. We can also measure ink gloss on these prints. Delta E and Color LAB values can be read on these prints ensuring equivalent film thickness on the same media.
Pigment Strength & Transfer (Wedge Prints):
This test yields data that shows you the printed density that can obtained at various ink film thickness. It is not a bleach test. It considers both ink pigment strength and well as viscosity and transfer. A print is made from a modified grind gage that can be measured for density values. Changes in this test between ink batches can be directly correlated to dot gain, mileage etc. problems on press.
Dry Rub Resistance:
Solid prints are made at a controlled ink film thickness, dried, and evaluated for rub resistance. Sheetfed prints are dried in a simulated lift for 24 hours and evaluated @ 20sweeps with a 4 lb. weight. Web inks are printed and dried, then chilled in the GATE HeatSet tester to any desired web exit temperature, or 269o F (recommended). Inks without coating are evaluated with the Sutherland Rub tester for 20 sweeps (SF) and 40 sweeps (Web) with a 4 lb. weight. Any sample can also be coated with either an aqueous or UV coating. These samples are evaluated with a Taber Abrasion tester.
Material that will evaporate in a still oven at 155oF, (68oC), defines the measurement of the volatile oils in an ink film. Soya, linseed etc. are non-volatile materials. Hydrocarbon oils are volatile. The % of volatiles in an ink formulation is a critical to monitor in a printer’s raw materials program, and can also assist the technician in troubleshooting press problems.
This test measures the percent trap values for the Blue, Red and Green traps. Prints are made with a strip of tape down the center to see how well the inks trap without the aid of the paper. We look for values above 75% on the paper and above 50% on the tape.
Water Pickup & Contamination:
This test measures the inks ability to absorb fountain solution in a Duke emulsification tester over five minutes. The results can be correlated to certain press issues. We also measure the pour off fountain solution or distilled water for conductivity contamination. If ink has insufficiently washed flush pigments calcium salts can leach into the fountain solution ruining its effectiveness.
Centipoises are measured after 5 minutes in a cone and cup viscosity instrument for dynamic testing at 90 degrees, to simulate press like conditions unlike static testing such as falling rod tests. We can test any type of ink from Flexo to EB offset.
This viscosity equipment utilizes the falling rod technology. This is an automated system and is used to monitor paste inks.
Fineness of Grind:
We use the ASTM method D1316-06.
Ink consumption is a function of the strength and transfer ability of an ink at a given film thickness as well as it propensity to set and split uniformly off the first and subsequent blankets. The evaluation includes the Paper & Ink Stability Test on standard paper combined with our Pigment Strength and Transfer test. With these results we can compare ink sets from batch to batch for variation and against typical industry values.