BS EN ISO 787-25 pdf free download
BS EN ISO 787-25 pdf free download. General methods of test for pigments and extenders.
6.2 Substrate, of minimum dimensions 150 mm x 50 mm, uniform, non-fluorescent, compatible with the binder to be used and appropriate to the method of colour comparison. Steel panels, contrast cards, lacquered cardboard sheets, aluminium-covered cards, standard art paper or glass slides may be used. If a glass slide is used, it shall be clear and colourless, and of the same thickness for the reference and test specimens. 6.3 Film applicator, for the application of the pastes of the test pigment and the agreed reference pigment to the substrate. 6.4 Stencil card (for covering specimens that are still moist when presented for measurement), approximately 0,5 mm thick, with a circular hole of diameter slightly greater than the size of the measure orifice of the spectrometer or tristimuius colorimeter (6.1), or glass plates of sufficient size to cover the specimen, coplanar, polished, colourless, about 1 mm thick. 6.5 Automatic muller, with ground-glass plates, preferably water-cooled. The plates shall be of diameter 180 mm to 250 mm and such that a known, selectable force of up to 1 kN may be applied to them. The driven plate shall be capable of rotating speed at between 70 min-1 and 120 min-1 and the apparatus shall have an arrangement for pre-setting the number of revolutions in multiples of 25. 6.6 Spatula, with flexible steel or plastic blade.
7 Sampling Take a representative sample of the pigment to be tested, as described in ISO 15528. 8 Procedure 8.1 General Take care that the results are not influenced by any temperature increase during the grinding operation. This applies particularly if the plates of the automatic muller are not water-cooled. If any influence is suspected, carry out preliminary tests to check this. Precondition of new muller plates occurs by milling a pigment in a suitable binder for 1 000 revolutions with a load applied to the plates. Remove and discard the paste. Before use, check that the surfaces of each plate have an even, matt appearance and are free from notch marks and polished areas. 8.2 Test portion 8.2.1 Generals Take a sufficient quantity of the pigment so that, when mixed with the appropriate amount of test medium (5.3), the resulting paste extends almost to the edges of the muller plates. Weigh this test portion to the nearest 1 mg.
8.2.2 White pigments Preferably use the recommended quantities of pigment and test medium given in Table 1 (see also 8.2.2, NOTE 1 and NOTE 2.) 8.2.3 Coloured and black pigments The mass ratio of pigment to binder depends not only on the oil absorption of the pigment but also on the viscosity of the mix during the milling operation. As a first step, all pigments can be allocated to one of the following three groups: Group a: pigments of low binder demand一pigment concentration 65 % (mass fraction) Group b: pigments of medium binder demand – – pigment concentration 40 % (mass fraction) Group c: pigments of high binder demand – pigment concentration 25 % (mass fraction) In order to give approximately 2 ml of mixture in each case, preferably use the recommended quantities for the appropriate group as given in Table 2 (see also NOTE 1 and NOTE 2). . NOTE 1 If the pigment/ binder mix chosen is found to be too stiff or fluid for use on the muller, one of the other pairs of quantities given in Table 1 or Table 2 can be used as appropriate. NOTE 2 If the diameter of the muller plates is near the maximum of the range specified in 6.5, it might be necessary to increase the quantities specified in order to reduce wear on the plates. 8.3 Preparation of pigment dispersions Take the appropriate quantities of the test medium and the agreed reference pigment (8.2.1 or 8.2.2). Place the test medium in the centre of the lower plate of the automatic muller (6.5). Sprinkle the pigment into the test medium and mix together, using the minimum effort, with the aid of the spatula (6.6). Distribute the paste at several points at a distance of about 35 mm from the centre of the lower plate or spread in the form of a ring with an internal diameter of 40 mm and an external diameter of 100 mm.BS EN ISO 787-25 pdf download.
