H. (hair - hydraulic mortar)

Hair - Hair has long been used as a binding material in lime and gypsum plasters. The best hair should be long, strong, and free from grease and other impurities. Ox hair is common, but horse, goat, and even human hair have been used as substitutes. The use of human hair is rare because of its fineness and poor strength. Short cropped hair is frequently found, and failures from ìlumpsî of hair sometimes occur where they have caused weak spots.
Ashurst (1983)

Hard finish - A mixture of gypsum, plaster, and lime applied as a finish coat, usually over rough plastering, then trowelled to provide a dense, hard, smooth finish. RS Means Building Glossary (undated)

Hardener - An unstandardised name for a substance that is mixed with another to make the second material harder and more durable. Hardeners are used in paints, varnishes, adhesives and cements. Other more specific names for materials that may be considered hardeners are: catalyst; initiator, accelerator, drier or filler.
Museum of Fine Arts, Boston (2000)

Hemp - A general name given to any of several coarse, durable bast fibres obtained from a variety of plants, e.g., Hibiscus cannabinus (Deccan hemp, kenaf, paco-paco), Cannabis sativa (Indian hemp), Musa textilis (Manila hemp- see abaca) or Agave sisalana (Seisal hemp- see sisal). Indian hemp, also called true hemp, is an ancient crop cultivated in Asia for its fibres as early as 2800 BCE. Hemp fibres range from 1-2 meters long and are yellow to brown in colour. They have a high cellulose content with little lignin. Hemp is lustrous, strong and durable with ,good resistance to water, salts, light and insects. 
Synonyms: Indian hemp; marijuana; ganja
Museum of Fine Arts, Boston (2000)

High-calcium lime -   A type of lime composed primarily of calcium oxide or calcium hydroxide and containing a maximum of 5% magnesium oxide or hydroxide. 
 RS Means Building Glossary (undated)

High-magnesium lime - The product resulting from calcining dolomitic limestone or dolomite and containing 37%-41% magnesium oxide or hydroxide, as compared to the 5% contained in high-calcium lime. 
RS Means Building Glossary (undated)

Horsehair - The hair from the manes and tails of horses. Horsehair is usually coarse and strong. Horse hair has been used for plaster binders. 
Synonyms: horse hair
Museum of Fine Arts, Boston (2000)

 HTI  (High Temperature Insulation) powder ? Finely ground refractory ceramic products which will react with lime to produce hydraulic properties in mortars.
 Ashurst (1983) 

Hydrated lime - Calcium hydroxide powder prepared by slaking lime with water, producing a  dry, relatively stable product. Hydrated lime, or slaked lime, is finer, purer and has more consistent usage properties than unslaked lime. Hydrated lime has replaced quicklime in most applications.
Synonyms: slaked lime
Museum of Fine Arts, Boston (2000); RS Means Building Glossary (undated)

Hydraulic cement -  A cement that hardens by the chemical reaction with water. The main types of hydraulic cements are based on one or more of the following compounds: calcium silicate (Portland cement), calcium-aluminate, magnesium oxychloride, pozzolana, slag, lime, barium silicate/barium aluminate or gypsum. These compounds react exothermically with water to harden into a water resistant solid. 
See also Roman cement, and Portland cement.
Museum of Fine Arts, Boston (2000)

Hydraulic hydrated lime -  The dry, hydrated, cementitious product resulting from the process of  calcining a limestone containing silica and alumina to a temperature just below incipient fusion. The resultant lime will harden under water. 
 RS Means Building Glossary (undated)

Hydraulic lime - A type of lime, calcium oxide, that will harden under water. Hydraulic lime contains a mixture of lime and clay and is composed of at least ten silicates
Synonyms: hydraulic cement
Museum of Fine Arts, Boston (2000); RS Means Building Glossary (undated)

Hydraulic mortar - See hydraulic cement
Museum of Fine Arts, Boston (2000)
 
 

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