Click here for the following calculators:
|Freeness - SR to CSF Calculator |
|Convert between degrees Schopper-Riegler to Canadian Standard Freeness |
|Pulp/Paper Strength Calculators |
|Convert between strength indices and absolute terms |
|Pulp/Paper Strength Calculators |
|Refining Power Converter Energy to Work Equivalents |
|Fibre Contacts |
|Estimate the theoretical number of fibre contacts per fibre in a thin paper sheet |
Air Dry Calculators
Customers sometimes ask Canfor Pulp to explain how air dry weights are calculated. On this page we try to explain how the calculations are made, what the terms mean and we provide a link to an interactive model where you can explore the calculations yourself. More »
Two of the most important tissue properties (besides some others such as softness, absorption, etc.) are strength and bulk. Strength is measured as tensile strength in MD and CD (machine and cross machine direction).Bulk is a term typically used in tissue which actually means thickness or caliper. Sometimes it is expressed as a specific volume measure (volume/weight) obtained by dividing the bulk (or caliper) by the basis weight. As tissue is compressible, so that a true specific volume cannot be easily obtained.
The caliper measurement is dependent on the effective pressure used during the measurement, and the way the measurement is executed. Some further explanation is provided under caliper or bulk measurement.
There are differences in the standards and methods used in tissue companies.
The basic factors are the width of the test strip (15mm, 25mm, 50mm were typically encountered), the length of the strip (typically from 100mm to 200mm), the number of plys used in a measurement (typically 1 or 2), and the speed of the clamps when the test is executed. The result is expressed as force/width per number of plys (typically 1 or 2) and this can be consolidated to the same dimensions using conversion factors. However, different results are found on the same samples when the testing parameters are different. When exactly the same test method is used, the results will get statistically closer.
Stretch, which is measured during the tensile test, tends to be more variable still, even when measured with the same method but on different equipment.
Canfor Pulp Innovation is equipped to do this testing so that the strength requirements and strength results of a tissue customer can be compared and well understood.
The strength requirements (and other tissue properties) can be quite different In geographical tissue markets, by region, by country or in the case of N. America, by continent.
There is an advantage in selecting the measurement conditions such that a converted finished tissue product can be measured in close to the same conditions as the base sheet, but this is not always the case. Tissue strength is reduced by most converting operations and the loss of strength for given operations can be important. Strength degradation in converting is one of the factors that can be influenced by the furnish composition and furnish quality, in which the use of Canfor’s softwood pulp can have a positive effect.
Strength and stretch are not independent of other important tissue properties, such as basis weight, softness and bulk.
Standard bulk or caliper measurements for tissue exist, are well documented and covered by standards (SCAN, DIN, ISO etc.). Tissue companies may use an industry standard, however these tend to use a small diameter foot and a relative high pressure. Small changes in caliper are not detected as a result and the method is less useful for comparing finished tissue product bulk or caliper against base sheet caliper. Also a more sensitive caliper measurement can be related to roll wind quality and diameter of the finished product roll.
Canfor Pulp can measure standard caliper, or a more sensitive caliper using a larger diameter foot, a lower pressure and precise timing.
Other Tissue Related Measurements
Canfor Pulp Innovation has a well equipped lab that can do various chemical analysis, fibre analysis, special low basis weight hand sheet capability for simulating tissue base sheets, and other. Pilot plant refining as mentioned in the general section of this website, is an important aspect of furnish preparation for tissue. Canfor Pulp maintains a database of finished tissue paper products from major markets coinciding with Canfor Pulp’s tissue client base. This data base includes, besides the above mentioned measurements, the furnish composition in terms of hardwood and softwood.