HPMC (Hydroxypropyl Methylcellulose) is a water-soluble polymer used as an additive in wall putty. It is used to improve the physical and chemical properties of the putty, such as its water retention, adhesion, and workability. It also helps to reduce cracking and shrinkage, and improves the durability and finish of the putty. HPMC is a cellulose-based polymer that is derived from plant sources, such as cotton, wood, and other cellulose-containing materials. It is a non-toxic, non-irritant, and non-allergenic material that is safe for use in wall putty. HPMC is also used in other construction materials, such as paints, plasters, and mortars, to improve their properties. HPMC is an effective additive for wall putty, as it helps to improve the workability and durability of the putty, and helps to reduce cracking and shrinkage. It also helps to improve the adhesion of the putty to the wall surface, and helps to improve the finish of the putty. HPMC is a cost-effective and environmentally friendly additive for wall putty, as it is derived from renewable sources and is non-toxic and non-irritant.