The hair used by the plasterer in order to make his "coarse stuff" hang together is obtained from the tanner's yard.
It should be long, sound, free from grease and dirt, thoroughly separated, beaten up, or switched with a lath, so as to separate the hairs, and dried.
It is classed according to quality as Nos. 1, 2, and 3, the last being the best. A bushel weighs from 14 to 15 lbs.
White hair is selected for some work, but as it should all be thoroughly covered by the coats subsequent to that in which it occurs, its colour is not of importance.
This is thoroughly mixed with long sound ox hair (free from grease or dirt, and well switched, or immersed in water to separate the hairs) in the proportion of 1 lb. hair to 2 cubic feet of the stuff for the best work, and 1 to 3 for ordinary work.
The sand is generally heaped round in a circular dish form; the lime, previously mixed with water to a creamy consistence, is poured into the middle. The hair is then added, and well worked in throughout the mass with a rake, and the mixture is left for several weeks to "cool," i.e. to become thoroughly slaked.
"If mixed in a mill the hair should only be put in at the last moment, or it will get broken and torn into short pieces.
"If there is sufficient hair in coarse stuff for ceilings, it should, when taken up on a slate or trowel, hang down from the edges without dropping off.
"For walls the hair may be rather less than in top stuff for ceilings." 1
Fine Stuff is pure lime slaked to paste with a small quantity of water, and afterwards diluted with water till it is of the consistence of cream. It is then allowed to settle; the water rising to the top is allowed to run off, and that in the mass to evaporate until the whole has become thick enough for use. For some purposes a small quantity of hair is added.
Plasterer's Putty is pure lime dissolved in water, and then run through a fine sieve. It is very similar to fine stuff, but prepared in a more careful manner, and is always used without hair.
The last-named ingredient causes the mixture to set very rapidly, and it must be mixed in small quantities, not more being prepared at a time than can be used in half an hour.
The proportion of plaster used depends upon the nature and position of the work, the time available for setting, the state of the weather, etc., more being required in proportion as the weather is damp. An excess of plaster causes the coating to crack.
It is used for finishing walls and for cornices. In the latter the putty and plaster should be in equal proportions.
This material has been described at page 179.
This process has been described at pages 206, 207; and also at page 407, Part II., and need not therefore be repeated.
For plastering on lath work and other coats the following directions of the patentees should be rigidly followed'.
They have already been given in Part II., but are here repeated to make these Notes more complete in themselves.
"For Plastering on Lath Work. - To the same quantities of water and prepared lime, as given, add only 6 or 8 bushels of clean sharp sand and 2 hods of well-haired lime putty; the hair being previously well hooked into the lime putty. When the mill is used, the haired putty should only be ground sufficiently to ensure mixing. Longer grinding destroys the hair.
"Lime putty should be run a short time before being used, to guard against blisters, which will sometimes occur.
"N.B. - This mixture will be found to answer equally well for ceilings as for partitions. If the sand is very sharp, use only 6 bushels of sand for covering the lath, and when sufficiently set, follow with 8 bushels of sand for floating (or straightening).
"Setting Coat and Trowelled Stucco. - For common setting (or finishing coat of plastering), the ordinary practice of using chalk lime putty and washed sand is recommended. But if a hard selenitic face is required, care must be taken that the prepared selenitic lime be first passed through a 24 by 24 mesh sieve, to avoid the possibility of blistering, and used in the following proportions : - 4 pails of water; 2 bushels of prepared selenitic lime (previously sifted through a 24 by 24 mesh sieve); 2 hods of chalk lime putty; 3 bushels of fine washed sand.
"Selenitic Clay Finish. - 5 pails of water; 1 bushel of prepared selenitic lime; 3 bushels of prepared selenitic clay; 2 bushels of fine washed sand; 1 hod of chalk lime putty.
"This mixture, well hand-floated to a fair face, and then well trowelled, will produce a finished surface equal to Parian or Keene's cement, and will be found suitable for hospital walls, public schools, etc. Being non-absorbent, it is readily washed.
"The use of ground selenitic clay improves the mortar, and renders it more hydraulic.
"When the selenitic clay is used, 2 bushels may be added to 1 bushel of prepared selenitic lime, the proportion of sand, ballast, etc., being the same as for prepared selenitic lime. The use of selenitic clay effects a considerable saving, as it is much cheaper than lime.
"For Outside Plastering use 6 or 8 bushels only of clean sand, and for finishing rough stucco face use 4 or 5 bushels only of fine washed sand, to the proportions of lime and water given."
Rough Cast is composed of washed gravel mixed with hot hydraulic lime and water. It is applied in a semi-fluid state, as described at page 409, Part II.