The main objective of applying _____________ to the plastered surfaces is to create a smooth surface.
🔬 Understanding Surface Finishing on Plaster
Standard cement plastering on walls provides a strong and durable surface, but it often has minor undulations and a relatively coarse texture. To achieve a perfectly smooth, level surface ready for high-quality paints, an additional finishing layer is required.
POP (Plaster of Paris): A type of building material based on gypsum. It is a fine white powder that, when mixed with water, forms a paste which sets and hardens. Its primary use in this context is as a finishing plaster to create a very smooth, level, and seamless surface over the initial cement plaster.
⚖️ Detailed Analysis of the Options
Let's examine why POP is the correct choice for creating a smooth surface and why the other options are not.
(c) POP (Plaster of Paris)
Function: Applied as a thin finishing coat (punning) over cement plaster. Because of its fine particles and smooth working properties, it can be troweled to a perfectly flat, non-porous finish, hiding all imperfections of the underlying plaster. This smooth base is essential for achieving a good finish with modern paints like emulsions.
Role: Surface leveling and smoothing material.
(a) Gum
Function: Gums (like gum arabic) are natural adhesives or binders. They are used in some traditional paint formulations (like watercolor) but are not used as a plastering or surface smoothing material for walls.
Role: Binder/Adhesive.
(b) Varnish
Function: A transparent, protective coating, typically used on wood to enhance the grain. It is not used on plastered walls and is not a material for smoothing surfaces.
Role: Protective, transparent coating.
(d) Distemper
Function: A type of inexpensive, water-based paint. It is a decorative final coat itself. Distemper is applied *to* a surface; it is not used *to create* a smooth surface. In fact, for a good distemper finish, the wall should first be smoothed with POP or a similar material.
Role: Decorative paint coating.
💡 Study Tips for Wall Finishes
- POP for Perfect: Associate POP with creating a "perfectly" smooth surface ready for paint.
- Distinguish Material from Coating: Recognize that POP is a building material used to prepare the surface, while Distemper and Varnish are coatings applied on top of the prepared surface.
- Think of the Layers: The typical wall finish is built in layers: 1. Masonry Wall -> 2. Cement Plaster (for strength) -> 3. POP (for smoothness) -> 4. Primer -> 5. Paint (like Distemper or Emulsion).
- Gum is Glue: Remember that gum is essentially a type of glue or binder, not a wall finishing product.