The main factors for the yellowing of the surface of the water-resistant putty After material research, a large number of experiments and engineering practice, the author believes that the main factors for the yellowing of the surface of the water-resistant putty are as follows :

Reason 1. Calcium hydroxide (ash calcium powder) back to alkali causes yellowing Calcium hydroxide, molecular formula Ca (OH) 2, relative molecular weight 74, melting point 5220, pH value ≥ 12, strong alkaline, white fine powder, slightly Soluble in water, soluble in acid, glycerin, sugar, ammonium chloride, soluble in acid to release a lot of heat, relative density is 2.24, its clear aqueous solution is a colorless, odorless alkaline transparent liquid, gradually Absorbed, calcium oxide becomes calcium carbonate. Calcium hydroxide is moderately strong alkaline, its alkalinity and corrosiveness are weaker than sodium hydroxide, calcium hydroxide and its aqueous solution are corrosive to human skin, clothing, etc., but non-toxic, and should not be in direct contact with skin for a много времени.

Method 2. For old wall decoration, the low-grade ordinary putty that is not water-resistant and easy to pulverize has been scraped before. Before using high-grade water-resistant putty, technical treatment should be done first. The method is: first spray water to wet the wall surface, and use a spatula to wipe it Remove all the old putty and paint (until the hard bottom) and clean it up. After the wall is completely dry, clean it up again and apply the backing agent to cover the backing treatment, then scrape the water-resistant putty. желтый.