Arrange the pressing plates (4.2.4), blotters (4.2.3) and sheets for pressing in the following sequence, commencing
from the bottom:
a) one pressing plate;
b) two dry blotters;
c) the laboratory sheet covered by the filter papers;
d) two dry blotters;
e) one pressing plate;
f) two dry blotters;
g) the next laboratory sheet covered by filter papers, etc.
Press the pack thus formed in the hydraulic press (4.2.5) for 1 min, applying a pressure of approximately 300 kPa to
the sheets (often different from the pressure gauge reading), having verified that the pack is centralized on the
pressure platen before applying the pressure.
After pressing, loosen the filter papers from the laboratory sheets, but leave them to protect the sheets. Dry the
sheets at room temperature to a moisture content of 5 % to 15 % by hanging them with the filter papers in a current
of dust-free air. The drying time shall not exceed 24 h.
Press the dried laboratory sheets, protected by the filter papers, in the press (4.2.5) at a pressure of 300 kPa to
500 kPa for 30 s to make them as flat as possible.
6.2.2 Sheet former procedure
Follow the instructions given in the relevant parts of ISO 5269-1 or ISO 5269-2 but make sheets with a grammage
of 200 g/m2. Use distilled water or water of equivalent purity.
Dry the laboratory sheets in the drying device (4.3.2) in the air at room temperature to a moisture content of 5 % to
15 %. Leave the two nearest blotters in place as a protection, or replace them by new blotters. The drying time shall
not exceed 24 h.
As regards the number of laboratory sheets to be prepared, follow the instructions given in 6.2.1.
7 Storage for subsequent brightness measurement
Protect the sheets from contamination and from exposure to light and heat. The ISO brightness of the sheets should
be measured immediately, according to ISO 2470, and in no case later than 4 h after drying has been completed.
8 Test report
The test report accompanying the laboratory sheets shall include the following details:
a) precise identification of the sample;
b) a reference to this International Standard;
c) precise identification of the laboratory sheets;
d) the number of disintegrator revolutions in the case of pulp in sheets or slabs;
e) type of apparatus and filter (filter paper or wire screen) used for the production of the laboratory sheets;
f) date and time of sheet making;
g) if a retention aid has been used, the kind and amount of retention aid;
h) if pH has been adjusted to 6,5 ± 0,5, this should be stated;
i) any particular points observed in the course of the sheet making;
j) any departure from this International Standard and any circumstances that may have affected the sheets.