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Adapting the use of plaster of Paris for use in hospitals, however, took some time. In 1828, doctors in Berlin were treating leg fractures by aligning the bones in a long narrow box, which they filled with moist sand. Substitution of plaster of Paris for the sand was the next logical step.
With judicious heating, gypsum converts to the partially dehydrated mineral called bassanite or plaster of Paris. This material has the formula CaSO 4 ·( n H 2 O), where 0.5 ≤ n ≤ 0.8. [ 8 ] Temperatures between 100 and 150 °C (212–302 °F) are required to drive off the water within its structure.
While working in Haarlem at the military hospital in 1851, Mathijsen first used plaster of Paris as a bandage. [1] Until then a Belgian method was used with starch that took up to a day to dry and harden. [1] Across the street he watched workers repairing cracks in the church with strips of jute dunked in plaster of Paris.
When the dry plaster powder is mixed with water, it rehydrates over time into gypsum. The setting of plaster slurry starts about 10 minutes after mixing and is complete in about 45 minutes. The setting of plaster of Paris is accompanied by a slight expansion of volume. It is used in making casts for statues, toys, and more. [19]
Filler material can also be removed chemically. Typically, chemical removal is used once the bulk of filler material is left and only a small portion is left. Unlike adhesives, fills tend to be easier to remove from ceramics. Plaster of Paris is one example of a fill that comes apart easily with warm. [6]: p.37
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Gypsum mortar, also called plaster of Paris, was used in the construction of many ancient structures. It is made from gypsum, which requires a lower firing temperature. It is therefore easier to make than lime mortar and sets up much faster, which may be a reason it was used as the typical mortar in ancient, brick arch and vault construction.
Elektrische Gipssäge, by Ortopedia, Kiel, Germany. A cast saw is an oscillating saw used to remove orthopedic casts.Instead of a rotating blade, cast saws use a sharp, small-toothed blade rapidly oscillating or vibrating back and forth over a minimal angle to cut material and are therefore not circular saws. [1]