What's the matter with yellowing after interior wall renovation and putty? This is related to the old wall and the use of heavy calcium putty powder

舊墻膩?zhàn)邮褂昧舜罅康腜VA膠水，膠水老化分解，產(chǎn)生不飽和酸，不飽和酸與膩?zhàn)又锈}離子反應(yīng)，生成相應(yīng)黃色的鈣鹽。

A lot of PVA glue is used in old wall putty. The glue is aged and decomposed to produce unsaturated acid, which reacts with calcium ion in putty to produce corresponding yellow calcium salt.