This standard specifies a method for determining the fineness of grind of paints, varnishes and printing inks by use of a suitable gauge, graduated in μm.
This standard is applicable to all types of liquid paints, varnishes and related products, except products containing pigments in flake form (e.g. glass flakes, micaceous iron oxides, zinc flakes).
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 3186 Paints, varnishes and raw materials for paints and varnishes - Sampling (GB/T 3186-2006, ISO 15528: 2000, IDT)
GB/T 20777 Paints and varnishes - Examination and preparation of test samples (GB/T 20777-2006, ISO 1513: 1992, IDT)
JB/T 9385-2017 Scraper fineness gauges
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
fineness of grind
reading obtained on a standard gauge under specified conditions of test, indicating the depth of the groove(s) of the gauge at which discrete solid particles in the product are readily discernible
4 Method A
4.1 Apparatus
4.1 Gauge
It can consist of a block of hardened steel e.g. 175 mm long, 65 mm wide and 13 mm thick.
At least for use with water-dilutable paints, a block of stainless steel shall be used.
The top surface of the block shall be both plan and ground smooth and shall contain one or two grooves approximately 140 mm long and 12.5 mm wide parallel to the longer sides of the block. The depth of each groove shall be uniformly tapered along its length from a suitable depth (for example 25 μm, 50 μm or 100 μm) at one end to zero at the other end and shall be graduated as specified in Table 1. A diagram showing two typical gauges is given in Figure 1.
The depth of the groove at any position along its length shall not depart from its nominal value at any position across the groove depth by more than 2.5 μm.
The surface of the block shall be finished by fine grinding or lapping; it shall be flat, with surface flatness of 12 μm and the straightness of cross section busbar of 1 μm. The top and bottom surfaces of the block shall be parallel within 25 μm.
Steel gauges of the approximate dimensions stated are suitable for the test, but other gauges giving similar results may be used.
The precision of the fineness-of-grind determination depends in part on which gauge is used (see Sub-clause 4.3). Therefore, it is essential to identify the gauge (100 μm, 50 μm or 25 μm) when reporting results or specifying requirements.
