Whitewashing — type of lime commonly used on building surfaces Which type of lime is most commonly used for whitewashing walls and ceilings?

Introduction / Context:
Whitewashing is a traditional surface treatment for interior and exterior masonry. Selecting the appropriate lime affects workability, setting, color, and finish quality. This question checks recognition of the standard practice in building maintenance.

Given Data / Assumptions:

• Whitewash is prepared by slaking lime and diluting to a brushable consistency.
• Substrate is plaster, brick, or concrete.
• No cement-lime paint admixtures are considered.

Concept / Approach:
Fat lime (high-calcium lime) after slaking forms calcium hydroxide paste with fine particle size, good plasticity, and brilliant whiteness. It carbonates slowly with atmospheric CO2 to form a uniform film. Hydraulic limes contain reactive silicates/aluminates and set with water; they are typically not chosen for whitewash appearance or ease of application.

Step-by-Step Solution:
Distinguish between quicklime (CaO) and slaked lime (Ca(OH)2).Recognize that whitewash uses slaked fat lime for workability and color.Select fat lime as the commonly used material.

Verification / Alternative check:
Traditional specifications call for well-slaked fat lime aged in vats for improved fineness and consistency, aligning with practice.

Why Other Options Are Wrong:
Quicklime must be slaked before use; hydraulic lime is better for mortars and renders; vague labels like ‘‘white lime’’ or ‘‘lime’’ do not specify the correct form.

Common Pitfalls:
Applying inadequately slaked lime can cause popping and poor finish; confusing limewash with cement paints may lead to cracking or peeling.

Final Answer:
Fat lime (high-calcium, slaked lime)