The discoloration of the paint mainly refers to the discoloration of the varnish. The varnish was originally a clear, colorless or extremely pale yellow, which turned brown or black after discoloration. The color paint also has a phenomenon of discoloration, which is mainly manifested by the dark color of the color paint.
The reasons for the discoloration of the paint may be as follows:
(1) The storage period is too long and the sediment is discolored.
(2) Gold and silver powder and varnish are prone to acid etching, making the paint color green, dark, and tarnished.
(3) Turpentine oil easily produces reddish brown pigment in iron drums.
(4) The ester solvent in the varnish reacts with the iron container and becomes black after being exposed to water.
The prevention and control method is:
(1) A coating which is discolored by precipitation, if it is not a quality problem, can be used after thorough stirring.
(2) For the shellac varnish which is most prone to discoloration, it is packed in a non-metallic container.
(3) Add gold powder and silver powder before using varnish. Do not store it in varnish too early.
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