What is Water Absorptiveness?
Water Absorptiveness also known as the Cobb Value is the function or method to determine the characteristics of paper, paperboard & corrugated boards including the porosity, sizing, and fiber compositions. This process is performed on various sheets or non-bibulous i.e. highly absorbent paper or paperboards in order to determine the relative rate of penetration of aqueous solutions such as water or other solutions. It indicates the degree of the surface and internal sizing. This method is not designed for the water resistance test and neither to measure the resistance to minute quantities of a liquid, but it is introduced to test how much water a material can absorb in a given period of time so as to check the penetration strength of the material. If a specimen absorbs more water, then it will be considered as unappropriate materials to fulfill the purpose of packaging and if a specimen absorbs less water, then it will be considered as most appropriate materials to fulfill the purpose of packaging.
Best Way to Test Water Absorptiveness of Paper & Paper Board
The best way to perform cobb sizing test is Cobb Sizing Tester. The instrument is designed to allow one side of the specimen to be wetted firmly right from the moment the soaking period initiate and allows instant removal of excessive water from the sample at the end of the test.
Presto Stantest manufactures high-quality of Cobb Sizing Tester, which is designed in compliance with various national and international standards like TAPPI T 441, ISO – 1060(Part 1) – 1966. The instrument helps to calculate the Cobb value i.e. the mass of water absorbed in a specific time by 1 square meter i.e. (10.76 sq. feet) of paper, board, or corrugated fiberboard in 1 cm of water.
Specifications of the Instrument as per the Standards
- Specimen Holder –
- Type: Metal ring type holder with a machined lower face,
- Internal Diameter of the holder: 28 ± 0.02 cm (4.44 inch.) {Correspondent to the cross-sectional area of 100 cm2, 2.5 cm high and about 0.6 cm thick
The holder is clamped duly to the flat base plate above the rubber mat (which is larger than the outside dimension of the ring.
- Metal Roller – It is a solid brass or stainless steel (corrosion resistant material) with a smooth face of 20cm wide and 10.0 ± 0.5 kg.
- Timer – Stopwatch is used to measure the test duration.
- Graduated Cylinder of 100 ml is affixed to the device.
- GSM Balance – With an accuracy of 0.01 g or better.
- Standard Test Area of the instrument – 100 cm2
(Device with test areas 25 cm2 and 10 cm2 are also provided on demand)
Standard Specification to Fulfill Test Requirement & Materials
- Reagents – Water, deionized or distilled.
- Specimen Size – Square shaped sample of size 5 x 12.5 cm (4.9 x 4.9 in.)
- Specimen Type – Wrinkle-free and fold-free sample\
- Test Duration – Normally 60 seconds or 120 seconds (for a paper) and 4 minutes and 45 seconds or 5 minutes for very hard papers and boards.
Presto Stantest design and manufacture Cobb Sizing Tester as per the above-mentioned specifications that are duly mentioned in standard TAPPI T 441, ISO – 1060(Part 1) – 1966.