Why is it better to print labels with the semi-rotary offset system?

Rotatek Brava 350 and 450 machines offer the best value for money on the market

The offset printing system offers the best value for money in label printing, taking into account the three main conditioning factors that define the current market:

  • Increasingly shorter runs.
  • Sales prices marked by increasing competitiveness.
  • The printer needs to make a profit on every single job.

The belief that offset is too complex to work with labels persists in the market but, the semi-rotary system for wet offset printing used by our Brava 350 and 450 machines (the latter also with the possibility of rotating) streamlines all processes. It offers the best quality with materials, inks, and standard consumables without the need for format changes.

Compared to flexography and digital printing, semi-rotary offset takes care of medium and short runs with total reliability, and with the lowest costs. This allows offering competitive prices and a convenient profit margin for the printer.

Let’s take a closer look at the advantages and disadvantages of each technology.


Flexography is the most widely used technology for adhesive label printing. However, many variables must be taken into account to achieve good quality works

  • Polymer characteristics.
  • Type of adhesive.
  • Type of scraper used.
  • Volume and condition of the chosen anilox.
  • Ink transfer: the anilox lineature must be at least six times higher than that of the polymer.
  • Type of ink (water-based, solvent, or UV).
  • Material of the front to be printed.
  • Presence of dust in suspension: particles can be embedded in the polymer and affect the printing.
  • Dot gain: it is very high, so it requires good preprinting control.

To achieve the best results, flexography requires a deep knowledge of the system. Neglecting any of the variables mentioned will affect the quality of the printing.

Undoubtedly, flexography has points in its favor, such as the good color coverage and its stability throughout the printing process. Also, the fact that it generates very little waste, the good image quality in non-porous materials, or the ease of in-line finishes. Even so, we cannot forget that it is a very demanding system, with competitive disadvantages such as:

  • High preprinting costs, especially in short runs and high-resolution digital polymers.
  • The variety and diversity of technological advances make it necessary to fit the machine with multiple plate cylinder holders or printing developments.
  • Depending on the image layout, there may be a need to print the same color in two groups and therefore configure more printing groups than required by an offset machine.
  • You have to spend a lot of time cleaning it.
  • A high risk of polymer deterioration during printing proportional to the definition and line screen requirements.
  • Polymer replacement times are long (a minimum of four hours), during which the machine must be stopped.
  • Textured substrates pose the risk of printing failure.
  • There is no standard Pantone color guide. The formulations depend on each manufacturer, the type of ink, and the chosen contribution (anilox).
  • Solvent-based inks require the installation of additional security and waste treatment systems.
  • High ink consumption: a minimum of 3.5 cm3 per m2.
  • Color space lower than offset, which limits the number of colors to be used in four-color print. The dot gain curve stands out in halftones but is critical in highlights and shadows.

Semi-rotary wet offset

The offset system is the most used in commercial printing, publishing, advertising brochures, and generally in all those works that require the highest quality. Due to low preprinting costs and higher quality demands from customers, in recent years it has also started to be used for label printing 

The semi-rotary technology does not need different printing formats and is conditioned by few variables:

  • A good fountain solution: treated water, not too hard with a PH within the specifications and at a temperature between 15 and 17ºC.
  • Correct levelling, pressure adjustment and roller parallelisms.
  • Stable ink-water balance during printing.

The weak points of the offset system are the low contribution of ink, which, requires the incorporation of a flexographic unit to the machine for varnishing. And also a somewhat higher waste than the flexographic unit because it is an indirect print. On the other hand, the strengths are numerous:

  • Good color coverage, guaranteed by twenty-roller batteries with three ink rollers and the high pigmentation of UV ink.
  • Good color stability during printing.
  • Excellent image quality whatever the substrate.
  • In-line finishing.
  • Inexpensive preprinting costs: an offset plate is 15-20 times cheaper than a flexographic polymer.
  • With a single print format allows any advance on the labels between 200 and 400 mm in 1 mm increments.
  • Allows the reproduction of any color, regardless of patterns and backgrounds.
  • Cleaning times are very short.
  • Minimal risk of plate deterioration during printing.
  • Very fast replacement time (10/15 minutes).
  • Printing on textured fronts offers the same quality as on any other material.
  • A standard Pantone color guide is available.
  • Ink waste is minimal.
  • Very low ink consumption: 1.2 cm3 per m2.

Digital printing

Traditionally, digital printing is the chosen system for short runs, as it is the most profitable in quantities of less than 250/300 m2, or 750/900 linear meters of material with a width of 330 mm. Usually, companies do not use it as the main technology, but as a complement to offset or flexographic equipment.

Digital printing is traditionally the system of choice for short runs, as it is the most cost-effective for quantities of less than 250/300 m2, or 750/900 linear meters of material with a width of 330 mm. Normally, companies do not use it as their main technology, but as a complement to offset or flexo equipment.

Some of the disadvantages that it presents are:

  • Limited materials availability: most require a previous treatment, and not all are ready for this type of printing.
  • Pantone colors only reproduce faithfully in hexachromic and heptachromic selections.
  • The finishes require a second operation which demands having a finishing machine.
  • There is a total reliance on the manufacturer of the equipment for inks, consumables, and accessories.

As stated at the beginning of this article, the conclusion is that the semi-rotary offset system offers the best quality at the lowest price with fewer constraints to be aware of. Rotatek Brava machines answer all market demands for label printing and allow both roll and cut sheet finishing (a very useful feature for paper labels).