GB/T 1724-2019Paints, varnishes and printing inks - Determination of fineness of grind (English PDF)

3.1 Fineness of grind

The readings obtained on a standard fineness gauge under the specified test

conditions. Such readings indicate the depth of the fineness gauge groove at which

the discrete solid particles in the product can be easily distinguished.

5.1 Instrument

The fineness gauge and scraper shall meet the requirements of JB/T 9385-2017.

The accuracy of the fineness of grind depends on the used fineness gauge (see 5.3).

When reporting the results or specifying the requirements, the specification of the

fineness gauge shall be specified (150µm, 100µm or 50µm).

5.2 Sampling

See 4.2.

5.3 Test procedures

5.3.1 Perform the preliminary tests to determine the optimum specification of the

fineness gauge and the approximate grind fineness of the sample (see Table 2 and

Paragraph 2 of 5.3.5). Such results of approximate measurement are not included in

the test results. The sample shall be tested in parallel for three times.

Table 2 - Typical Fineness Gauge Scales and Recommended Test Range Unit: µm

5.3.2 Place the washed and dried fineness gauge (see 5.1) on a flat, horizontal, non-

sliding surface.

5.3.3 Pour a sufficient amount of the sample into the deep end of the groove and allow

the sample to overflow slightly. Be careful not to entrain the sample with air when

pouring the sample.

5.3.4 Hold the scraper with the thumbs and forefingers of both hands (see 5.1); place

the blade of the scraper on the deepest end of the groove of the fineness gauge; touch

the surface of the fineness gauge; make the long side of the scraper parallel to the

wide side of the fineness gauge; moreover, the scraper shall be pressed

perpendicularly to the surface of the fineness plate; so that the scraper and the long

side of the groove form an right angle. The scraper is scraped across the entire surface

of the fineness gauge at a uniform speed within 3s to a position where the depth of the

groove is zero. In the case of printing inks or similar viscous liquids, in order to avoid

the low results, the time required for the scraper to scrape the entire groove length

shall be no less than 5s. Apply sufficient downward pressure on the scraper to ensure

Specification of fineness gauge Scale interval Recommended test range

the groove is filled with the sample and the excessive sample shall be scrapped off.

5.3.5 After the sample is scrapped, immediately (no greater than 5s) observe the

fineness gauge from the side as soon as possible. When observing, the sight line and

the long side of the groove shall form a right angle; and the angle with the surface of

the fineness gauge shall be 15°~30°; meanwhile, observation is required to be

conducted under light that is easy to see the condition of the sample in the groove.

If the flowability of the sample causes a flat pattern can't be obtained after scraping

and coating, a minimum amount of suitable diluent or paint base solution can be added

and manually stirred; then followed by repeated test. Any dilution shall be indicated in

the report; sometimes, the diluted sampled may occur flocculation and affect the

fineness of the grind.

5.3.6 Observe the sample position where the dense particles appear firstly; record the

readings (accurate to the minimum scale) on the groove position where the particles

appear uniformly. If there are individual particles exposes to other scale lines, then the

number of the particles in the range between readings and the adjacent scale line shall

not exceed 3 (see Figure 4).

Figure 4 - Example of Fineness with Readings of 45µm

5.3.7 Immediately use suitable solvent to clean the fineness gauge and scraper after

each reading.

5.4 Results expression

The test results take the arithmetic mean of two readings that are close to each other,

accurate to the minimum scale of the fineness gauge. The difference between two

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