As for the particle size, the finer the particle is, the better the water retention property will be. When cellulose ethers of large particles are in contact with water, the surface will be immediately dissolved to form a gel and wrap the materials up so as to prevent water molecules from continuing to penetrate. Sometimes stirring for a long time, it cannot get uniformly dispersed or dissolved but form a turbid flocculent solution or agglomeration, significantly affecting its water retention effects of the cellulose ether. Solubility is one of the factors in selecting cellulose ethers.

The fineness is an important indicator that affects the performance of HPMC. HPMC used in dry mortar powder requires for not only low water content, but also fineness of 20% to 60% as well as the size less than 63um. The fineness affects the solubility of HPMC. Coarser HPMC is usually granular, and easily dispersed and dissolved in water without caking. But the dissolution rate is very slow, so it should not be used in the dry mortar.

Coarser HPMC in fineness is not only a waste, but also will reduce the local strength of mortar. In the large-scale construction of such dry mortar, it shows that the cure rate of the local dry mortar significantly decreases and cracks occur due to different curing times. As for spraying mortar in mechanic construction, since the stirring time is short, the requirement for the fineness is higher. The fineness of HPMC also has a certain impact on its water retention property. In general, as for HPMC of the same viscosity but different fineness, in the case of the same addition amount, the finer it is, the better the water retention effects will be.