Dolomitic Hydrated Lime Type S

The magnesium-oxide component of dolomitic quicklime requires high pressure levels or long slaking periods to hydrate completely.

Hydrated S

Dolomitic Type S hydrated lime products are produced by adding water to quicklime in closed containers called autoclaves. The autoclave provides the high pressure needed to completely hydrate magnesium oxide.

The chemistry of the reaction is as follows:

CaO-MgO + 2H2O → Ca(OH)2-Mg(OH)2

The hydration reaction breaks the quicklime down into fine particles of hydrated lime. The sizing of the hydrated lime is further modified by milling the product to ensure consistency. The dolomitic products produced with this process are defined as Type S hydrated lime as defined by ASTM C206 and C207. These products are characterized by a fine particle size distribution and high surface area. This results in products that have high levels of plasticity and water retention.

Type S dolomitic hydrates are useful in construction and industrial applications.

Type S Construction Products:

The Niagara dolomite found in Northwest Ohio is considered to be one of the best deposits in the world for the manufacture of lime products with high levels of plasticity and a bright white color for construction applications. Type S hydrated lime products can be used in these applications without soaking for long periods of time. This speeds the construction process and makes blended product performance more predictable. 

Graymont produces Type S hydrated lime products that serve several construction applications.


Graymont manufactures Type S hydrated mason's lime products under two brand names, Mortaseal® and Super Limoid S® (East Coast brand). When properly combined with sand and/or cement, they create a lime-based mortar having superior performance and ageless durability. Due to the low air content of these products, Mortaseal ®and Super Limoid S® provide exceptional bond strength in mortars. 

Both of these products comply with ASTM C207 (hydrated lime for masonry purposes) specifications. They are available in durable, three-ply, weather resistant and poly-lined 50-lb. (22.5-kg) bags, or for delivery in pneumatic bulk tankers.


IVORY® and SNOWDRIFT® finishing limes are made from high-purity dolomitic limestone and autoclaved for immediate use with gauging plasters without soaking or slaking. These products are formulated to be compatible with standard gauging plasters. Use IVORY® or SNOWDRIFT® Finish Lime with high-strength gauge, Keenes cement, and all other manufacturers' gauging plasters for high plasticity, tight bonding and smooth troweling - important features sought by plasterers. These finishing limes permit a thin finish coat, while the gauging plaster provides initial set and early hardness to minimize shrinkage of lime, for either smooth trowel or textured sand-float interior finishes. Walls become exceptionally hard and crack-resistant while maintaining their long-lasting beauty. Both products comply with ASTM C206 Type S requirements for finishing lime. They also comply with ASTM C207 Type S requirements for masonry applications. These products are available in 50-lb. (22.5-kg) bags or for delivery in pneumatic bulk tankers.


Graymont hydrated spray lime is a fine-grind Type S hydrated lime product used for whitewashing as well as agricultural applications. The fine particle size and white color of this product contribute to excellent performance in whitewash applications. Graymont hydrated spray lime can also be used for agricultural purposes. This product contains calcium and magnesium nutrients that are beneficial for plant growth. Graymont hydrated spray lime is faster acting and has higher neutralizing value than ag-lime or high-calcium hydrated lime products. This product is available in 50-lb. (22.5kg) bags.

Industrial Products:

Type S hydrated lime products can be used for a wide range of industrial applications, thanks to their fine particle size and high chemical availability. Kemidol® Superhydrate is a Type S dolomitic hydrated lime product characterized by a fine particle size distribution and high surface area. The magnesium hydroxide contained in Kemidol® Superhydrate is beneficial in certain industrial processes, such as silica removal. Kemidol® Superhydrate also has a high neutralizing power. This product is available in 50-lb. (22.5-kg) bags, bulk bags, or for delivery in pneumatic bulk tankers.

Did you know?

There are three distinct types of limestone, defined by their magnesium carbonate (MgCO3) concentrations. These types are Dolomitic (35 to 46% MgCO3), Magnesian (5 to 35% MgCO3) and High calcium (less than 5% MgCO3).