238. Finishing Coat

Finishing Coat. Sometimes this coat is omitted, in cheap work, when the walls are to be papered, the brown coat being smoothed as well as possible. This method is not a good one, as the rough plaster is likely to mar the smoothness of the paper.

There are several kinds of finishing coats, such as troweled stucco, rough sand finish, hard-finish white coat, etc.

238 Finishing Coat 237

Fig. 108.

In all cases the material is applied to the wall in the form of a stiff paste, by means of the steel trowel a, as shown in Fig. 109, and is spread uniformly over the surface to a thickness of about 1/8 inch.

The troweled stucco, consisting of fine stuff and very fine white sand, to which a little white hair may be added, is thoroughly polished to a glazed finish with the trowel a', the surface being kept moist by water applied with the brush b. This is frequently called the skim coat.

Rough sand finish may be produced on the stucco by covering the hand float with a piece of carpet or felt, which will cause the sand to rise and present the characteristic sandpaper surface. It may also be made by using more and coarser sand with the lime putty.

238 Finishing Coat 238

Fig. 109.

Hard-nnished white coat consists of gauged stuff, smoothed and polished with the steel trowel; as this material sets rapidly, care must be taken to observe that the second coat is well dried; otherwise, the unequal shrinkage will cause hair cracks to occur all over the finishing-coat. Marble dust is frequently mixed with the gauged stuff to give greater hardness and a surface susceptible of higher polish, about equal quantities of marble dust and plaster of Paris being used.