[serial] paint inspector, I want to say to you (3) - "fine" operation, reading "degree", how to do a good paint "fineness" test?

In daily inspection, GB / T 1724-1979 and GB / T 6753.1-2007 are the two most commonly used standards for Fineness Test methods In principle, no matter which standard, it is necessary to find the place where the particles on the fineness plate begin to appear intensively Let's follow the test steps, first of all, sort out the operation process: Environment: indoor, dust-free, windless, good light, do not require constant temperature and humidity, room temperature is OK Test bed: flat, clean and of suitable height Sample: stir evenly, avoid a lot of bubbles, and distinguish whether the test object is the main agent or after mixing Fineness board: flat, dust-free, stain free, remember to select the model of fineness board Scraper operation: appropriate amount of sample at the top, stable knife holding, pressing the board surface, scraping from top to bottom at a constant speed Reading: tilt the two hand holding plate downward slightly, the depth is on the left and the shallow is on the right, and find the starting point of dense particles In some places of the test, we need to pay special attention to: bubbles: during the mixing and mixing of the paint, the generation of bubbles should be minimized Before the test, the sample should be left for a period of time to avoid the confusion of bubbles and particles after the scraper Scraper: the operation shall be stable, fast and compact At least, the scraper shall cross the "0" scale line at a constant speed Never stop halfway Reading: do not expect to read the result at one time Due to solvent volatilization and other reasons, the reading time specified in the standard is very short First, we need to judge whether the range of fineness plate is appropriate according to the situation of the plate surface, then determine the approximate reading range, and finally, we need to scrape several times to determine the reading when we know it Don't focus on counting "3" and "5-10" at the beginning It's not too late to finally determine the upper limit of the strip Standard: select the fineness plate in strict accordance with the range specified in the standard, and report the results in strict accordance with the reading accuracy of the fineness plate The result of 35 μ M can not be reported with ISO fineness plate Whether it's Meng xinxiaobai who just stepped into the laboratory, or the old driver who has stuck to the test bench for ten years, "fineness" test must be a very difficult mountain for paint inspectors You don't know what kind of coating products you will encounter, what kind of state it will present on the fineness board, and you will even be at a loss when facing many varnish products But what I want to tell you is that you will have confidence in your results if you carefully do every step of the operation and accurately read against the standard [guide] paint inspector, I want to say to you (4) - do you understand the operation of coating scratch in corrosion test? Related wonderful article (click on the topic to read) [serial] paint testing personnel, I want to say to you (1) - from the experience of assistant w cleaning the windowsill [serial] paint inspector, I want to say to you (2) - Determination of nonvolatile content, have you done it right?