METHOCEL™ 228S is a surface-treated hydroxypropyl methylcellulose (HPMC) thickener. It is a water-soluble, high-purity, nonionic cellulose ether that yields a viscosity of 5,000 cPs at 2% in water. METHOCEL™ 228S is surface treated to delay hydration. This delayed hydration allows for lump-free solutions of METHOCEL™ 228S to easily form in aqueous formulations. When used in tape–joint compounds and crack fillers, METHOCEL™ 228S imparts excellent workability, crack resistance, and viscosity control. METHOCEL™ 228S also enhances water retention, extending the open time of the formulation.

In gypsum and cement plasters and masonry mortars and grouts, the water-retaining performance of METHOCEL™ 228S provides better mechanical strength through slower evaporation and loss of moisture when in contact with other porous materials. The water retention that METHOCEL™ 228S provides also improves the visual appearance and strength of these materials by reducing cracking issues.