Topic of your interest
Residual strength of heatset papers
In combination with the embrittlement of the paper due to heatset drying, the mechanical stresses during folding lead to a significant reduction in strength properties. This can lead to breaking of the fold. It is often noticed too late when individual pages of the finished printed product are torn out of a staple or thread binding.
Complaints caused by fold breakage or tearing off of individual pages are often associated with high costs, since the problem is usually first noticed by the end unser. If the problems already occur at the printing machine, expensive downtime and a longer production time must be reckoned with.
With a residual strength test it is possible to check papers for their suitability in advance of production. Furthermore, in the event of a complaint, it can be determined whether the cause has a material or production-related background.
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The residual strength test is a reliable laboratory method that can prevent major damage to print production. Contact me without obligation, I will be happy to advise you!
To determine the residual strength, we need at least ten sheets of the paper to be tested in DIN A4 format. You can also specify which folding direction is to be tested (parallel or crosswise to the paper fibre).
Please send the paper sheets to:
Fogra Forschungsinstitut für Medientechnologien e.V.
Department Printing Techniques
85609 Aschheim b. München
The residual strength is determined according to the Fogra method listed in DIN 19306-2. For this purpose a test line is used, which consists of a laboratory dryer (Fogra-HOT), a folding instrument (Fogra-FI) and a tensile strength tester. In the HOT the paper samples are dried with hot air, similar to heatset machines. The defined fold is then made in the FI. Finally the tensile strength tester measures the force required to break the fold.
The average breaking strength of 20 paper samples is used as the characteristic value for the residual strength. Based on experience from numerous expert opinions and research projects, it can be assigned to a critical, medium or non-critical range.
Testing of a paper grade with fold along a selectable direction:
€ 142.95 (Fogra member) | € 196.50 (regular)
I would be happy to send you a non-binding offer for residual strength testing of heatset papers: