How to determine the surface drying time of the coating?
Prepare the coating on the base plate specified by the product, and then dry it according to the dry operation conditions specified in the product standard. -
Every few times or the time specified in the product standard, within the range of not less than 1cm from the edge of the coating, use the following methods to check whether the surface of the coating is dry.
(1) Cotton blowing method Gently put a cotton ball on the surface of the coating, and blow the cotton ball lightly along the horizontal direction with the mouth (10~15) cm away from the cotton ball. If it can be blown away, no cotton will be left on the film surface. Silk, that is, the surface is considered dry. (2) Finger touch method Touch the surface of the coating lightly with your fingers, if you feel a little sticky but no coating sticks to your fingers, the surface is considered to be dry. The surface-drying time of paint coatings for interior and exterior walls of buildings is mostly determined by the finger touch method.
How to determine the actual drying time of the coating?
The methods for measuring the actual drying time of the coating include the filter paper method, the cotton ball method, the blade method and the thick layer drying method. The first two methods are often used in the determination of the solid drying time of architectural coatings.
(1) Press filter paper method Put a piece of qualitative filter paper (smooth surface in contact with the coating film) on the coating film, then gently place the desiccator on the filter paper, and start the stopwatch at the same time. After 30 seconds, remove the drying Tester, turn the sample over (with the coating film facing down), the filter paper can fall freely, or tap the back with the index finger of the hand holding the plate a few times, the filter paper can fall freely and the filter paper Fibers are not stuck to the coating, the coating is considered to be actually dry.
For coatings that are allowed to be viscous as specified in the product standard, if the filter paper still cannot fall freely after the sample is turned over and tapped with the index finger, place the sample on a glass plate, use tweezers to hold a corner of the pre-folded filter paper, and Gently pull the filter paper in the direction. When the sample plate does not move and the filter paper has been pulled down, the coating is considered to be actually dry even if there are filter paper fibers sticking to the coating, but it should be indicated that the coating is slightly sticky.
(2) Cotton ball pressing method Put a absorbent cotton ball on the surface of the coating, place the drying Tester gently on the cotton ball, and start the stopwatch at the same time. After 30 seconds, remove the drying Tester and cotton balls, and leave them for 5 minutes to observe whether there are traces of cotton balls on the coating; traces and loss of light, if there are (1~2) cotton threads left on the coating, It can be lightly dusted off with a cotton ball, and the coating is considered to be actually dry.
(Recommended instrument: drying time Tester)
