Show fit first st plaster was Vas mud now Is delicate item mankind mankind in all probabilities used mud ns as its ita first plastic material applying the mud over a framework of woven reeds then further along in the iho worlds history tile the burning of lime and the of gypsum wore were discovered up until about 1 SO 10 years ago lime was the standard plastering material out but lime plaster because of its chemical composition takes a long time to reach its ultimate hardness and it Is dangerous to apply a decorative material I 1 over a lime plastered wall until the plaster has completed the chemical process L known as the set neres heres why willie while still on the process of setting lime Is liable to blister or to burn through a decorative in material at erial gypsum plaster on the other hand sets so rapidly that material to slow up the process of setting t has to be introduced thus the setting time Is 3 actually controlled and gypsum plaster that 11 setd in two hours its shipped to those cities where a two hour set la 13 required a plaster that sets in four hours Is shipped where a four hour set Is required etc both gypsum and litile lime plasters are arc incombustible and thus add to the lire safety of a structure in which they are used often a lime putty finish coat is used over base coats of gypsum plaster in tills this case the lime la is gunned gun gull ged with gypsum guaring plaster to prevent shrinkage and to give the lime an initial set sel such a lime finish coat Is thinly applied because of this thinness the lime coat cuu can get enough carbon dioxide out of the air to complete its set NIt within liln a reasonable length of time |