Lime putty – preparation, storage, and screening for plastering works Which statement best reflects correct practice regarding lime putty used in building works?

Introduction / Context:
Lime putty is the traditional binder for fine plastering and lime washes. Quality putty improves workability, finish, and durability of lime mortars. This question tests knowledge of correct preparation and handling practices for lime putty in construction projects and conservation works.

Given Data / Assumptions:

• “Lime putty” refers to fat (high-calcium) lime putty unless otherwise specified.
• Hydraulic lime sets with water and is typically used as a powder or gauged mortar, not aged as putty in the same way.
• IS sieve No. 300 is a fine screen; screening alone does not “make” putty.

Concept / Approach:

Proper lime putty is produced by slaking quicklime with ample water to form calcium hydroxide paste, then aging (maturing) the paste under water. Aging improves plasticity and reduces unreacted particles. Fat-lime putty can be stored for weeks to months in sealed, wet conditions, improving quality with time. Screening helps remove grit but does not replace correct slaking and maturation.

Step-by-Step Solution:

Verification / Alternative check:

Conservation manuals and traditional plastering guides emphasize slaking and aging for fat-lime putty and note that properly stored putty remains usable well beyond three days.

Why Other Options Are Wrong:

Made from hydraulic lime: Not typical; hydraulic lime behaves differently and is commonly used as a powder.

Only up to three days: False; well-stored putty lasts much longer.

Obtained by drying a sieved mix: Screening removes grit but does not create putty by itself.

All of the above: Incorrect because several statements are wrong.

Common Pitfalls:

Using inadequately slaked lime; skipping maturation; allowing putty to dry out; confusing fat and hydraulic lime practices.

Final Answer:

It is made by slaking lime with water and allowing it to mature