Polymetaal

These rubber rollers are rarely used for black ink. The technical construction of these rollers differs from leather rollers. The surface of a rubber roll is soft and smooth, without irregulatities that can keep the ink or water, like with a leather roller.
Synthetic rubber rollers are heavier than leather rollers, with the risk that too much ink is transferred to the stone. Therefore, do not use too much pressure during the inking process. Color ink is often softer and "shorter" than black ink, which allows an easy transfer to the stone. This makes an even distribution of the ink more difficult.

Example: Most ink is transferred to the stone during the first revolution of the roll. During this process the roll collects some moisture on the surface. During the next revolutions the layer of the transferred ink will be thinner, which may cause a lighter area between the parts that have been inked during the first revolution and the later ones. The quantity of the moisture on the roll has been doubled in the meantime. By rolling in all directions the distribution will become better, but the distribution will never be as with a leather roller. The natural irregularities of the leather roller allow an even distribution of water and ink over the stone, also during multiple revolutions.
Learning to roll with a rubber roller requires training and craftmanship, certainly for inking larger stones.

On the image on the right is shown an inking pattern, that may help for solving problems while inking bigger stones. One has to find a way of inking in which lighter and darker areas even eachother out. It is possible that the roller requires more ink more regularly. It is even possible that the properties of the ink have to be changed, to make it more "sticky" (longer). Some printers do not want to make a whole revolution, but prefer short banners. These banners must then cross eachother, making a "fishbone structure". Images with different tone strengths per color are relatively easy to ink with a synthetic roller. The different tone values in the image cover up already fast irregularities during the inking process. Good inking, especially for large stones is always a problem regardless the roller. In some cases a large diameter roller can help, because the overlaps are less.

Another problem for a synthetic roller, however not a very serious problem, is the lack of structure in thre surface. A leather roll can, to a certain extent, absord moisture from the stone. This moisture remains on the surface of the roller and emulsifies with the ink, making the composition of the ink different. This ink cannot be used anymore, and has to be refreshed.

A summary;

• Do not use a lot of pressure. The weight of the roller should do the job.
• Roll in the stone quite quickly, to make the distribution of the ink as good as possible.
• Don't use too much water for dampening the stone. Then the roll will not absorb too much water either.
• Refresh the ink on the inking stone regularly. This can be after two or three prints, but also after each print. One to three lines with a spatula is enough. If the ink becomes "like rubber" it should be replaced by fresh ink.
• Make in advance the "roll-schedule" to avoid overlap problems.
• Change the ink properties if required ( shorter or longer ). Use ink conditioners to do that.