Potato starch is a popular choice for formulators of cementitious and gypsum based plasters. It can impart favorable rheological properties not usually obtainable without the addition of more expensive products such as OPC, gypsum, kaolin, attapulgite, and cellulose ethers. It is probably included in low cost, DIY quality latex paints to increase viscosity instead of using costly ingredients like acrylic and titanium dioxide which would provide superior dry coverage.
While it is an excellent thickener for it's cost, I haven't seen any evidence of thixotropy, water retention, drying shrinkage reduction, or any adhesion benefits. As such, it would probably be best retained for formulation of budget constrained trowel applied finishes rather than being included in formulations for pumpable mixes requiring a shear thinning boundary layer, or used as a final rheology modifier in those formulations which already meet necessary parameters at a higher water content.
