The bubble method uses the flow velocity of air bubbles in the liquid to measure the viscosity of the paint product. The measured viscosity is also the kinematic viscosity, which is only applicable to transparent varnishes. The Gardner Holdt bubble viscometer is commonly used in the industry. Standard solutions of different viscosities are sealed in a set of glass tubes of the same specification, numbered, and the samples to be tested are put into tubes of the same specification . Next, turn it over with the standard tube and compare the moving speed of the air bubbles in the tube to find the viscosity number of the closest standard tube, which is commonly known as the viscosity of the standard tube number. From A5 to Z10, there are currently 41 grades. It is also possible not to compare with the standard tube, but to measure the time for the bubble to rise, and use the number of seconds as the unit of viscosity. Viscosity under conditions such as number and second can be converted into standard kinematic viscosity or dynamic viscosity, see Table 4-3-4.
The inner diameter of the standard tube is 10mm±0.5mm, the total length is 113mm±0.5mm, draw a line at 100mm±1mm and 108mm±1mm from the bottom of the tube, that is, the liquid is filled to the mark of 100mm±1mm, and the plug is closed. To the scale of 108mm±1mm, the length of the bubble is 8mm±1mm.
