Uncoated offset paper

Hello dear offset printing specialists, Technologists. There is a question why the paint dries very long on such paper? Traditional sheet offset. Ph of water 5.0-5.3 all indicators are normal, and the paint on coated paper dries quickly.

 

Add a small drop of Cobalt drier 0.5% or paste drier to your ink, it's normal for uncoated papers to take longer in drying.

 

This is logical, but does not explain the reason for long drying.

 

Think of uncoated paper as a sponge. The vehicle of ink is what dries, it's oils, but uncoated paper draws those oils into the sheet minimizing their contact with air. There is little absorbtion on coated paper; the vehicle and pigment cure on the surface.

 

I would try substituting the cobalt dryer, which is basically a top dryer, with something that dries either from the bottom up, or a combination dryer which dries from the middle out, in both directions. Cobalt drier works great on a coated sheet, but not so well on uncoated papers. Even with the best dryers, you will have as mentioned earlier, a harder time drying on many uncoated sheets. The best way around this, whenever possible, would be to try scheduling your work so that you can allow overnight drying of these sort of jobs. Its also very important that you run the ink film thickness down as low as possible. Inks with strong pigment will be your friend when printing on these types of paper because you will be able to achieve color running less ink.

 

Super smooth uncoated sheets are outstanding for bright colors and near coated sheet like printed appearances. It’s because most of the ink just sits on the surface of the sheet, rather than absorbing into it. They’re also notorious for being very slow drying because of that..