The probable cause of tigerstripes, rivering, meandering, arching or zebrastripes

Below some thoughts on how the defect is generated and how to prevent it.

  • When a dyesub paper is printed small droplets of ink hit the paper
  • The coating on the paper is absorbing a big part of the watery fluid phase of the ink
  • The absorbed fluid is passed on to the fibres in the paper supporting the coating
  • This mechanism leaves us with a print side that is moist with a printed image, and a paper support that carries the rest of the moisture extracted from the ink
  • Usually the printed paper is heated by the drying capacity installed on the printer
  • This causes a major part of the moisture to evaporate from the printed surface
  • So usually the top of the printed paper is dry to the touch when wound up, with nobody taking notice of the fact that the paper itself still carries a considerable amount of moisture
  • It is exactly that moisture that is causing the problems with tigerstripes
  • The paper is put onto the calendar, and during the sublimation the paper is heated
  • This heating is causing the dyestuff to sublimate from the surface into the substrate
  • The water in the paper support of the coating changes into steam as a result of the heating
  • It is important to understand that the high transfer yield coating is capable to absorb water, but is practically impervious to vapors like sublimated dye or water
  • The steam is therefore trapped between the metal surface of the calendar cylinder and the coating
  • It will try to find a way out, and doing so it will lift the paper from the cylinder surface
  • At the places where the paper is lifted, no energy is available to sublimate the dyestuff, resulting in lighter parts in the transferred image
  • The “escape pattern” of the steam typically looks like the striping of a zebra or tiger

One remark: The stripes can also occur when the printed paper is transferred onto textile that is very close (because it is coated on one side or it is a sandwich with a non permeable foil). In that case, the vapors from dyestuff and moisture also have to find a way out. When that is the situation it is even more necessary to work with thoroughly dry paper (see also point 6.)

With the above in mind, the things you can do to prevent striping are:

  1. Apply as little ink as possible onto the paper. This also makes sense looking at costs, so creating a suitable profile will be profitable in more than one way
  2. Make the paper as dry as possible, not only on the printed side, but also (maybe even more important) the non printed side. Use the installed drying capacity
  3. Sometimes it helps to work with maximum fabric and felt tension on the calender
  4. Reverse calendering where the fabric is on the calendar cylinder and the printed paper on the outside is sometimes helpful
  5. If no drying capacity is available leaving the printed roll for a longer time on the shelf might help
  6. In extreme cases ( transferring onto substrates that are nearly nonporous) customers place a printed roll in a box and blow air through the box, actually drying the rolls for 4 – 24 hours
  7. It might be an idea to dry the printed paper on the transfer calendar, feeding it at a high speed and a lower temperature than transfer conditions.