What 
The force needed to bend the substrate without distorting its structure, i.e. without going beyond the elasticity modulus (Emodulus according to Young), expressed in mNm. 
Why 
Stiffness has impact on the runnability (troublefree feeding through a press or printer), but also on the look and feel of the substrate. For some applications (folding board) it is essential, e.g. boxes, wishing cards etc. 
How 
In a stiffness meter a sample of defined dimensions is bent over an angle of 5° and a distance of 50 mm. 
Calculation 
Report the average force of 10 significant values in both MD and CD and the standard deviation. 
What 
The force at the moment of bending the substrate can withstand without distorting its structure, i.e. without going beyond the elasticity modulus (Emodulus according to Young), expressed in mN. 
Why 
This is a property that has impact on converting operations for applications like wrapping paper, envelopes and some ways of bookbinding, but also on printing. 
How 
In a stiffness meter a sample of defined dimensions is bent over an angle of 15° or 7.5° and a distance of 50 or 10 mm. 
Calculation 
Report the average force of 10 significant values in both MD and CD and the standard deviation. 
Note 
This method only applies to paper up till 170 g/m². 
What 
The maximum force (Fmax) the substrate can withstand before it breaks, expressed in kN/m. 
Why 
On a press a lot of force is exerted on a substrate that may lead to deformation or rupture. 
How 
A strip of the substrate of 15 mm width is clamped between the grips of a tensile tester. Between the grips there is a distance of 180 mm. The upper grip travels with a speed of 25 ± 5 mm/min, until the substrate breaks. 
Calculation 
Report the average of 10 significant values in both MD and CD and the standard deviation. 
Note 
The tensile index is the average force divided by the weight of the substrate, expressed in N.m/g 
What 
The stretch of the fibre at the moment of break when the maximum force (Fmax) is applied, expressed in %. 
Why 
The stretch of a fibre has impact on the forces a substrate may withstand. In MD a fibre has more strength but less stretch, in CD this is the other way around. 
How 
A strip of the substrate of 15 mm width is clamped between the grips of a tensile tester. Between the grips there is a distance of 180 mm. The upper grip travels with a speed of 25 ± 5 mm/min, until the substrate breaks. At precisely that moment the stretch is calculated. 
Calculation 
Report the average of 10 significant values in both MD and CD and the standard deviation. 
What 
The extent of elasticity of the fibre, expressed in MPa. The Emodulus is a ratio calculated from tensile strength, stretch and stiffness of the sample. 
Why 
The stretch of a fibre has impact on the forces a substrate may withstand. As long as these forces are within the boundaries of the Emodulus, the substrate will keep its original structure. Due to greater speed of presses, thus generating more force, a printer needs to find a balance between speed and quality of the printed matter. 
How 
A strip of the substrate of 15 mm width is clamped between the grips of a tensile tester. Between the grips there is a distance of 180 mm. The upper grip travels with a speed of 25 ± 5 mm/min, until the substrate breaks. 
Calculation 
The Emodulus (E*) is calculated as: Where: Report the average of 10 significant values in both MD and CD and the standard deviation. 
What 
The energy working equivalent, expressed in J/m², also known as the amount of energy necessary to break the sample. 
Why 
Any force exerted on the substrate generates energy; the amount of energy absorption is an indication of other strength properties: the more energy is absorbed; the more forces the substrate can withstand. 
How 
A strip of the substrate of 15 mm width is clamped between the grips of a tensile tester. Between the grips there is a distance of 180 mm. The upper grip travels with a speed of 25 ± 5 mm/min, until the substrate breaks. The TEA is calculated over the total duration of the test, till the moment of break. 
Calculation 
Report the average of 10 significant values in both MD and CD and the standard deviation. 
What 
The theoretical length of a web with any width, that, when suspended freely, would break due to its own weight, expressed in metres. 
Why 
The theoretical length generates the tensile strength of the substrate. 
How 
A strip of the substrate of 15 mm width is clamped between the grips of a tensile tester. Between the grips there is a distance of 180 mm. The upper grip travels with a speed of 25 ± 5 mm/min, until the substrate breaks. 
Calculation 
Report the average of 10 significant values in both MD and CD and the standard deviation. 
What 
The maximum force (Fmax) the substrate can withstand before it breaks, expressed in kN/m, after the sample has been immerged in distilled water during an agreed upon time, e.g. 1 hour. 
Why 
This has impact on wrapping material that may be exposed to moisture. 
How 
A strip of the substrate of 15 mm width is guided underneath a bar above a wet finch mounted on the lower grip of a tensile tester and both loose ends are clamped between the upper grip. Between the grip and the finch there is a distance of 90 mm. After immersion the upper grip travels with a speed of 25 ± 5 mm/min, until the substrate breaks. 
Calculation 
where: Report the average of 10 significant values in both MD and CD and the standard deviation. 
Note 
The wet tensile index is the average force divided by the weight of the substrate, expressed in N.m/g 
What 
Ratio between tensile strength wet and dry, expressed in a %. 
Why 
To determine loss of tensile strength after immersion in water. 
How 
Tensile strength (both dry and wet) is determined conforming to the appropriate ISO standards.

Calculation 
where: Report the average of 10 significant values in both MD and CD and the standard deviation. 
What 
Determination of the internal bond of the fibres, being the maximum force the surface of a substrate can withstand without splitting of layers and/or fibres, expressed in kPa. 
Why 
Because a substrate may not delaminate, blister or split due to ink tack. Tack value of ink is the biggest at the moment the printing cylinder releases from the substrate. 
How 
The surface of the substrate is clad with double sided tape at both sides, after which it is mounted between two metal blocks of an area of 645 mm² which are suspended between the grips of a tensile tester. First these blocks are compressed at a constant force during 6 seconds, after which the upper block is set into motion. At the moment the force diminishes due to splitting, the maximum force is reached. 
Calculation 
where: σ ZD = Z directional tensile strength _ F = mean maximum tensile force in N Report the average of at least 3 significant figures and the coefficient of variation. 
Note 
For papers having a weight less than 60 g/m², results shall be treated with caution since the tape may reinforce the paper. 
What 
Determination of force needed to pull loose selfadhesive material that is adhered to itself, expressed in kN, thus determining the tack of the glue. 
Why 
Certain applications of selfadhesive material may need more tack than others (e.g. when the label needs to stick to a difficult surface like uncoated corrugated board) 
How 
The adhesive side facing each other, two samples of the same material of a width of preferably 25 mm are adhered together in such a way that the total length of the sample (≥ 200 mm) still has at least 50 mm left that does not adhere to each other. Before clamping the average thickness of the bond is determined. Both ends of 50 mm (X and Y in the figure above) are clamped in the grips of a tensile tester. The upper grip travels with a speed of 10 mm/min (or any other agreed upon speed) till at least 150 mm of the adhered end is pulled loose. 
Calculation 
Report the average force of at least 5 significant values over 100 mm, ignoring the first and last 25 mm of the peel, and the standard deviation. 
What 
Resistance of a substrate against out of plane tearing, measured in average force and expressed in mN. 
Why 
Due to high speeds that can be gained on a modern press, forces may lead to tearing of the web. Also paper that complies with the Standards ISO 9706 and/or NEN 2728 pertaining to ageing resistance of paper needs to achieve a minimum force before and after artificial ageing. 
How 
A strip of the substrate with a height of 63 mm is clamped into the Elmendorf Pro Tear and precut by a knife. Then a pendulum with a known weight is released, causing the substrate to tear. Generally, this test is performed with a layer of more sample strips at the same time. The amount of samples, gsm and thickness of one sheet are programmed beforehand so that software can determine the force for each single sample. 
Calculation 
Report the average of at least 10 significant values in both MD and CD and the standard deviation. 
Note 
The tear index is the average force divided by the average weight of the sample, expressed in mN.m²/g. 
What 
The number of times a substrate may be folded till it tears, expressed in log10 of the number of folds. 
Why 
For applications where the substrate needs to be often folded open and closed again, such as maps, installation drawings, building plans, it is important that the substrate does not tear at the crease. Also paper that complies with the Standards ISO 9706 and/or NEN 2728 pertaining to ageing resistance of paper, needs to achieve a minimum number of double folds before and after artificial ageing. 
How 
In a double fold tester strips of paper are clamped and mechanically folded two ways by a ‘knife’ with a constant force. A counter keeps track of the number of folds made. This number is converted to log10 values. Schematic view from above of one of the two positions on the Schopper apparatus: Test strip 100 x 15 mm 
Calculation 
Report the average of at least 10 significant values in both MD and CD and the standard deviation. 
Note 
Our tester can handle substrates with a maximum thickness of 225 µm (0.225 mm) 