HPMC plays three roles in thickening, water retention and construction of putty powder. Thickening: cellulose can be thickened to suspend, keep the solution uniform up and down, and resist sagging. Water retention: make the putty powder dry slowly, and assist the reaction of ash calcium under the action of water. Construction: cellulose has a lubrication effect, which can make the putty powder have good workability. HPMC does not participate in any chemical reaction, only plays an auxiliary role. Adding water to the putty powder and putting it on the wall is a chemical reaction, because new substances are generated. Remove the putty powder from the wall, grind it into powder, and then use it again. It is not enough, because new substances (calcium carbonate) have been formed. The main components of ash calcium powder are: a mixture of Ca (OH) 2, Cao and a small amount of CaCO3, CaO+H2O=Ca (OH) 2 - Ca (OH) 2+CO2=CaCO3 ↓+H2O ash calcium generates calcium carbonate under the action of CO2 in water and air, while HPMC only preserves water and aids the better reaction of ash calcium, which itself does not participate in any reaction.