Key Factors Affecting Gypsum Plaster Setting Time and How to Control It

Why Does Setting Time Become Unstable?

Gypsum plaster is valued for its lightweight, insulation, energy efficiency, and eco-friendly properties. However, in practice, unstable setting time often creates problems:

• Too fast

→ not enough working time for application;

• Too slow

→ cracking or powdering of the surface.

Main Causes

• Over-burned gypsum

→ Excess anhydrite causes shorter setting, later extended after aging.

• Under-burned or moisture-exposed gypsum

→ Hemihydrate converts to dihydrate, shortening setting.

• Environmental conditions

→ Heat and wind accelerate water loss, reducing setting time.

• Unstable retarders

→ Low-quality additives lead to inconsistency.

• No raw material testing

→ Fixed retarder dosage without testing causes unpredictable results.

Solutions

• Raw Material Control

Age gypsum for 1–2 weeks until stable; store in a dry, sealed place.

• Construction Environment

Avoid working in extreme heat, strong wind, or freezing conditions.

• Retarder Selection

Use stable, reliable retarders from trusted brands to minimize variations.

Conclusion

By controlling raw materials, environment, and retarders, unstable setting time can be avoided, ensuring:

• Better workability
• Higher efficiency
• More durable wall finishes