The process of white washing process can be done through carried out under the following operations:
22.4.1 Preparation of white wash
The white wash is prepared from fresh burnt shell or pure stone lime mixed with water. Shell lime is preferred to pure lime as it is whiter and slakes more perfectly to a smoother paste.
To prepare white wash, fresh lime is slaked at the site of work and is dissolved in a tub with sufficient quantity of water. After slaking, it is allowed to remain in the tub of water for 2 days and then stirred up with a pole until it attains the consistency of thin cream. This mixture is then strained or screened through a clean coarse cloth. Clean gum dissolved in hot water is then added at the rate of 2 kg/m3 of lime to the white-wash water. The solution so formed is called as white wash. To prevent the glaring effect due to whitewash, sometimes copper sulphate at the rate of 4 kg/m3 of thin cream is added. In order to have better adhesive properties, alum or common salt may be added in the same proportion as gum.
22.4.2 Preparation of surface
Before applying white wash to a new wall surface, it is essential that the surface should be cleaned, brushed and made free from loose materials and any other foreign matter. If the surface to be coated is oversmooth, then the coats will not stick to it. In such cases, the surface should be rubbed with sand paper to ensure proper adhesion of white wash.
In case of re-white washing, all loose materials and scales should be scrapped off. The old loose white wash is removed by rubbing with sand paper. All holes on the wall, irregularities of surface and minor repairs are corrected in advance by filling with lime putty.
All greasy spots should be given a coat of a mixture of rice water and sand so that the finishing wash may stick to the surface. If old white wash is discoloured by smoke or other reasons as in kitchens, factories, restaurants, etc., then in such cases the surfaces should be given a wash of a mixture of wood ashes and wastes or yellow earth, before the application of white wash. Cement plastered walls should be washed with a weak solution of soap and dried before applying white wash.
22.4.3 Application of white wash
The white wash is applied to a specified number of coats with a brush. Usually, three coats are required for new work and scrapped surfaces, while one or two coats are considered sufficient for old work. For each coat, one stroke is given from the top downwards and the other from the bottom upwards over the first stroke, and similarly one stroke from the right and another from the left over the first brush before it dries. Each coat should be allowed to dry before applying the next coat. The finished dry surface should not show any signs of cracking or peeling and should not come off readily on fingers when rubbed.