Felix Schoeller’s E-PHOTO® paper produces excellent print results without stress whitening
Whitebreak is a quality defect often found in layflat products such as photo books. Felix Schoeller Digital Media, one of the business units of the Osnabrück-based Felix Schoeller Group, joined forces with the Papiertechnische Stiftung (PTS) to develop a method for quantitatively measuring this attribute. The reproducible method they came up with ranked the specialty paper manufacturer’s E-PHOTO® papers as the clear winner.
High-quality layflat products such as photo books are still a relatively recent digital printing application, but it is enjoying strong growth. Photo books often use a layflat binding, which allows both pages to lie completely flat and enables photos to be presented to great effect across the entire width of the book. Different technologies and types of medium are used in this application, including the Felix Schoeller Group’s E-PHOTO® papers. When a layflat product, in which conventional photo printing paper has been used, is handled a great deal, undesirable whitebreak appears on the book’s centre fold, impairing the high-quality image.
To date there was no method for measuring whitebreak in layflat applications and describing it in quantitative terms. The Felix Schoeller Group joined forces with the Papiertechnische Stiftung (PTS) and together they set themselves the task of developing a standard method (PTS whitebreak test). It was used to examine the whitebreak behaviour of three types of paper which are used predominantly in photo books.
The papers tested were: a silver halide photo paper2. a standard coated paper3. an E-PHOTO® paper produced by the Felix Schoeller Group
E-PHOTO® papers emerge as the clear winner
The newly developed whitebreak test method is able to clearly differentiate the stress whitening behaviour of the different papers. Of the three papers tested, E-PHOTO® paper emerged as the clear winner, showing no whitebreak at all. The standard coated paper came in second. Depending on the number of folds, it showed clear whitebreak, increasing over time. The silver halide photo paper ranks as the poorest paper in this respect. Severe whitebreak occurred, even with a small number of folds.
The test samples were three different A4 papers that had been printed black. These papers were cut to a 208 mm x 60 mm format and folded using an Erichsen coater. The paper sample was folded so that the opposite edges lined up. It was then inserted into the coater. The fold was made using a calibrated doctor blade at a predefined speed. The samples were removed, unfolded and then smoothed with the doctor blade. This procedure was repeated to produce multiple folds in exactly the same place on the sample.
The areas showing whitebreak were measured using a VHX-500 digital microscope. This microscope has integrated image analysis software, which was used to identify and calculate the different areas with and without whitebreak. The readings (measured areas, sum of areas measured, the ratio between the areas as a percentage and the total size of the areas in µm²) were exported to a CSV file and processed using a spreadsheet.
PTS – Papiertechnische Stiftung
The Papiertechnische Stiftung (PTS), which is based in Munich and Heidenau, runs about 80 research projects a year, financed with public funding totalling EUR 8 million, making it one of Europe’s largest industrial research institutes. Its research objectives are tailored to industry’s needs and industry is actively involved in planning and carrying out the projects. PTS’s research areas concentrate on new materials, packaging, resource efficiency and print products. Its expertise is primarily based on collaborative research. Individual companies commission PTS to research particular issues or solve problems that are specific to them. This kind of research is tailored to the requirements of the company commissioning it. The results are available for the exclusive use of the company in question.
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