Problems in Offset Printing

1. Set-off

The appearance of any irregularities in the printing process can not only make production difficult but also negatively affect its quality. Therefore, it is worth knowing what problems can occur in offset printing and how to eliminate them. First, let’s focus on set-off – we will discuss its causes and point out methods that help prevent this issue.

Set-off of fresh ink occurs when ink transfers from lower sheets to upper ones. The causes of this effect in offset printing include:

• Excessive amount of ink on paper with low absorbency.
  Solution: use standard ink feeding, add auxiliary agents to the ink, apply anti-set-off powder, and regulate sheet stacking.
• Too high a delivery pile.
  Solution: the heavy paper weight squeezes the air cushion between sheets. To eliminate this, print on a lower pile and apply powder.
• Incorrect delivery adjustment.
  Solution: this problem occurs especially with heavy cardboard. Reduce the drop height and adjust gripper opening so the sheet lands tightly on the pile.
• Poor flatness of the printing substrate.
  Solution: choose better quality paper to avoid wavy edges.
• Electrostatic charging of sheets.
  Solution: use smaller, looser piles of paper to minimize the effect.

As you can see, many factors can lead to set-off. Fortunately, it can be controlled. For more practical tips on solving offset printing issues, we invite you to explore other articles on our blog.

2. Ink Rubbing Off

When producing prints, various difficulties may arise that negatively affect the aesthetics of the final result – therefore, it is worth knowing how to deal with them. There are many problems in offset printing and ways of eliminating them, and today we will focus on one of them: ink rubbing off. Let’s take a closer look at the causes of this issue and the methods of minimizing it.

Ink too heavily diluted

One of the causes of ink rubbing off from paper may be excessive dilution of the ink, which leads to problems in offset printing. This happens when the liquid component (the binder) is absorbed too quickly and too intensively by the substrate. As a result, there is no proper bonding with the pigment on the surface. The way to eliminate this error is to ensure pigment bonding with the substrate through overprinting with a binder or an oil-based printing varnish.

Improperly sized paper

Ink rubbing off can also be caused by improperly sized paper, which will have excessive absorbency. As a result, offset printing loses its quality. Similar to the previous case, the ink penetrates the paper too quickly, and the pigment does not bond with the binder. Such a substrate should be overprinted with oil-based printing varnish. Since oxygen-curing ink is used, the underprint may hinder absorption. If the run is already completed, the way to eliminate this problem in offset printing may be to overprint with binder, use overprint paste, or apply a glossy oil-based varnish.

Too little binder in the ink

Ink rubbing off can also be caused by an insufficient amount of binder in the ink used for offset printing. The solution is very simple – just add binder to the ink or apply an additional binder layer. This way, the visual effect of the print will improve, eliminating problems caused by ink rubbing off, which reduces both aesthetics and readability of the prints.

3. Ink Repelling

Various factors can lead to a decline in print quality and readability, including the type of paper or the quality of printing agents. One of the issues that may occur in offset printing is ink repelling. It is important to know that this error can be eliminated in order to avoid an unattractive final effect.

Causes of ink repelling in offset printing

The main reason for this problem is overly fast drying of the base ink and the formation of a layer that becomes too hard. Ink repelling occurs when the previously printed layer does not accept the next layer of ink because it has dried too much. This issue is usually caused by adding too much dryer or by leaving too long of a gap between printing the first and second inks. Fortunately, it is possible to avoid this error.

Methods of eliminating ink repelling:

• For low print runs, wipe the printing surface with cotton wool.
• For high print runs, apply a printing varnish and print the next layer of ink when the varnish is partially dry.
• Consider avoiding the use of a dryer altogether.

These guidelines can help prevent ink repelling in offset printing. Applying them allows you to avoid unattractive, unreadable results. However, it is important to remember that the choice of method should depend on the print run size.

Eliminating common offset printing problems

Reducing ink repelling ensures a neat and visually appealing result. Correct diagnosis of the problem is essential to achieve aesthetically pleasing sheets in both small and large print runs.