Troubleshooting Mirror ink

When drying the print in a line oven it sometimes appears hazy. Why does this occur?

Upon further investigation with the customer, the printing conditions that caused this hazy appearance were discovered to be as follows. Mirror Ink was printed with a cylinder press and dried in a line dryer at a high temperature, thus the resultant hazy effect. The reason being: the initial drying at a high temperature. The recommended drying condition is 30 minutes at 80°C, but in this case the line dryer was used for 2 minutes at 100°C. When the substrate was dried at this high temperature with a great deal of solvent on it, the substrate was affected adversely and turned white.

How can we dry in a line dryer without getting haze?

You may avoid the hazy effect with following countermeasures:

1. Lower the temperature of the line dryer. (lower than 80°C)

2. If the line dryer has several drying sections, set the temperature at the entrance section as low as 40-60°C and evaporate the solvent as much as possible (preferably 80-90%).

3. Then the printed matter can be dried at 80-100°C and evaporate the solvent completely. This should result in a good mirror effect.

Is over-printing required?

Yes. Over-printing is necessary not only to improve scratch resistance but also to improve resistance to other elements. As Mirror Ink is affected by moisture, the aluminum layer might change the color if not over-printed.

We recommend reading the following reports:

Excellent performance as protective layer of MIR ink

How can we increase covering power?

Use squeegee with 70 degree hardness and rather high printing pressure. When printing with Mirror Ink, the covering power may not be as good as what is shown in print samples. An effective measure to increase covering power is to use a harder squeegee. As the Mirror Ink has less resin in it, ink transfer to the substrate is rather lighter than with ordinary screen inks.

Therefore changing printing conditions is sometimes effective.

* Recommended printing conditions are as follows
Squeegee hardness should be 70 degrees. / Printing pressure should be slightly higher. / Doctor pressure should be slightly higher as well.