The turbidity of paint is mainly for varnish and cooked oil. Normal varnishes and cooked oils should be transparent, and the muddy injection is due to the following reasons besides poor quality during manufacture:
(1) The temperature is too low and there is too much water vapor
Some paints contain a small amount of water, wax and other impurities, which are easy to precipitate at low temperatures and cause varnish turbidity. Therefore, the room temperature should not be lower than 20°C during storage. It is recommended to place the paint bucket on a wooden frame so that the paint bucket does not touch the ground to prevent cooling. If the varnish is slightly muddy, it can generally be used as usual; if the turbidity is serious, you can use heating to remove water, or lay the paint flat, so that the water naturally sinks into the bottom of the paint; water.
(2) Improper choice of solvent or excessive dosage
Since varnish is a colloidal substance, its storage stability mainly depends on the solubility of various film-forming substances in solvents. If the type of solvent is not selected properly, some paints are not easy to dissolve, which will cause turbidity. Especially the medium-oil alkyd varnish, if it is diluted with No. 200 solvent gasoline, it will soon become seriously cloudy and even liver. Therefore, the medium-oil alkyd varnish that has been diluted with No. 200 solvent gasoline should be used up in a short time to avoid scrapping. For slow-drying varnishes caused by excessive use of solvents, an appropriate amount of turpentine can be added; for quick-drying varnishes (such as nitro varnishes), a little butanol or benzene solvent should be added to remove the turbidity. If it is seriously turbid or swollen and becomes pasty, it can only be used with putty.
(3) The paint quality is poor, and two kinds of paints with different properties are mixed
If too much lead drier is added to the slow-drying varnish, the nitrogen content of nitrocellulose used in the nitro varnish is too high, and the shellac paint contains too much wax, etc., it will easily cause turbidity. For paint that has become cloudy, it must be used up as soon as possible. . (4) The base material undergoes reactions such as polymerization. The base material of the coating, that is, resin or polymer, tends to continue to undergo polymerization and other reactions during storage, resulting in an increase in molecular weight and a decrease in solubility, which precipitates out and causes muddy processes.
