I. Common Issues in Putty Powder
Dries Too Quickly
Causes: Excessive calcium hydroxide (lime) content or low water retention of fibers; overly dry substrate.
Solutions:
1.Reduce lime content (recommended: 15%-25% of mix).
2.Use high water-retention cellulose (e.g., HPMC) at 3-5‰ dosage.
3.Pre-moisten the wall (especially in hot/dry conditions).
Peeling/Cracking During Application
Causes: Low-viscosity cellulose, insufficient dosage, or poor-quality additives compromising water retention.
Solutions:
1.Use mid-viscosity cellulose (80,000–100,000 mPa·s) with ≥95% water retention.
2.Increase cellulose dosage (3–5 kg per ton for interior putty).
Powdering (Lack of Adhesion After Drying)
Causes: Insufficient or low-purity lime; inadequate water retention delaying lime hydration (CaO → Ca(OH)₂ conversion).
Solutions:
1.Boost lime content (≥20%) or use high-active lime (≥85% Ca(OH)₂).
2.Ensure cellulose quality and allow proper curing (24+ hours before sanding).
Bubbling
Causes: Uneven/humid substrate or improper application (e.g., overly thick layers).
Solutions:
1.Prepare substrate: Fill voids, maintain moisture <10%.
2.Apply thin, multiple coats (≤1mm per layer); let each dry fully.
Pinholes/Curdling
Causes: Impure cellulose (e.g., CMC blends) reacting with lime; poor film-forming.
Solutions:
1.Use pure HPMC (avoid adulterated products).
2.Age lime powder (reduce reactive CaO content).
Cracking/Yellowing
Causes: Excess lime (brittleness) or high CaO content (carbonation yellowing).
Solutions:
1.Limit lime to ≤30%; add 1–2% redispersible polymer powder for flexibility.
2.Use low-CaO lime or substitute with calcium carbonate.
II. Why Does Putty Thin Out When Mixed with Water?
Thixotropy: Cellulose (e.g., HPMC) gives putty shear-thinning properties.
Behavior: Stirring breaks gel structure → reduced viscosity; resting restores thickness.
Note: Ensures smooth application but avoid excessive thinning (causes sagging).
III. Difficult Application (Hard to Spread)
Main Cause: Overly high cellulose viscosity (e.g., 200,000 mPa·s) or excessive dosage.
Fix:
For interior putty, use 80,000–100,000 mPa·s cellulose at 3–5 kg/ton.
Add 0.5–1 kg lubricant (e.g., starch ether) for smoother application.
