GB/T 1749-2025 in English

Background and significance of the standard revision

GB/T 1749-2025 "Determination of consistency of thick paint and putty" is the first comprehensive revision of the 1979 version of the standard. This revision conforms to the technological development needs of the coatings industry and improves the scientific nature and operability of the test method. While maintaining the core measurement principles unchanged, the new standard has comprehensively optimized the instrument requirements, test conditions and result presentation to better meet the testing requirements of modern coatings products.

Analysis of major technical changes

Compared with the 1979 version, the 2025 version of the standard has undergone significant upgrades in technical content:

Core measurement principles and key technical points

This standard adopts the principle of measuring the diffusion diameter of a fixed volume sample under a specified load. Specific technical points include:

Sample preparation: Sampling must be strictly in accordance with GB/T 3186 to ensure sample representativeness. When using an instrument to handle the sample, care should be taken to avoid introducing bubbles or altering the sample's original structure. Temperature Control: The test must be conducted at (23±2)°C. The specimen, pump, glass plate, and weight must be pre-conditioned at (23.0±1.0)°C. This stringent requirement minimizes the impact of temperature on the consistency measurement results. The new standard sets clear technical specifications for the measuring instrument: The pump consists of an outer sleeve and a plug, with an inner diameter of (29.7±0.2)mm and a depth of (29.0±0.2)mm. The metal material must be corrosion-resistant and have a smooth, defect-free surface. The glass plates are divided into two sections, A and B, measuring (200.0±2.0) mm × (200.0±2.0) mm × (6.0±0.2) mm. Glass plate A is engraved with 12 concentric circles, spaced 10 mm apart, for accurate reading of the flow spread diameter. The weights must be metal, with a mass of (2000.0±5.0) g, to ensure accurate and stable loading. Chapter 6 of the standard details the test procedures: First, place the pump housing in the center of glass plate B, fill it with the specimen, and smooth it. Use the pump stopper to press out the specimen, forming a standard cylindrical specimen. Move the sample to the center of glass plate B, cover it with glass plate A, and apply the weight load. Start the stopwatch for 60 seconds, and then read the flow spread diameter of the sample.

Key points: The sample should be filled densely without gaps; the cut should be kept flat when cutting the sample; when reading the result, if it is an ellipse, the average value of the major and minor axes should be taken.

Result judgment and quality control

The measurement results are expressed in flow spread diameter (cm). When the difference between the results of two parallel measurements is no more than 1.0 cm, the average value is taken and reported as an integer. If the difference exceeds 1.0 cm, the test must be repeated.

The current standard does not provide precision data, and the laboratory should establish appropriate precision requirements through internal quality control procedures.

Implementation Recommendations and Application Guidance

In response to the implementation of the new standard, paint manufacturers are advised to:

1. Update laboratory instruments and equipment to ensure that the specifications and parameters required by the new standard are met, especially the dimensional accuracy of the pump and the scale accuracy of the glass plate.

2. Establish a strict environmental temperature control system to ensure that test conditions meet the requirement of (23±2)℃.

3. Strengthen operator training and standardize the operating procedures for sample handling and result reading.

4. Establish an internal laboratory precision control procedure and conduct regular instrument calibration and personnel comparison.

The implementation of the new standard will significantly improve the consistency and comparability of the consistency measurement results of viscous products such as thick paint and putty, providing a reliable technical basis for product quality control and industry technical exchanges.