HPMC for putty powder is thickening agent and water-retaining agent. It also makes the construction more easier.
Thickening: HPMC will prove a suspension thickening, keep the solution of uniform and consistent effect, resist sagging.
water-retaining: HPMC will make the putty powder dry slowly and then to assist the calcium hydroxide reaction with the water.
Construction: HPMC has lubricating effect. It makes the putty powder good workability.
HPMC does not participate in any chemical reaction. It just play as a supplementary role.