Paint quality control determines whether every batch meets customer expectations or becomes a reject. IPCS sets up complete factory QC systems — instrument selection, parameter targets, batch record formats, daily check procedures and staff training. See also our paint technologist service and process optimization.
| QC Parameter | Instrument | Target (Interior Emulsion) | Why It Matters |
|---|---|---|---|
| Viscosity | KU Viscometer | 90–110 KU at 25°C | Application workability, sag resistance |
| pH | pH Meter | 7.5–9.0 | Emulsion stability, biocide efficacy |
| Fineness of Grind (FOG) | Hegman Gauge | 4–5 Hegman | Smoothness, gloss, colour uniformity |
| Contrast Ratio (Opacity) | Leneta Chart | ≥95% economy, ≥98% premium | Hiding power, coats needed |
| Dry Time | Touch/Hard test | Touch <30 min, Hard <2 hrs | Recoat time, film formation |
| Weight per Litre | SG Cup (100 mL) | ±2% of specification | Batch consistency, fill accuracy |
Frequently Asked Questions
What are the essential QC tests for emulsion paint?
Viscosity (Krebs Units), pH, fineness of grind (Hegman gauge), contrast ratio/opacity (Leneta chart), dry time (touch and hard), weight per litre (SG cup). For washable grades: scrub resistance per IS 101. Colour vs standard swatch.
How much does a basic paint QC lab cost?
A basic paint factory QC lab with KU viscometer, pH meter, Hegman gauge, Leneta charts, SG cups and standard swatches costs ₹25,000–75,000 to equip. IPCS specifies the minimum instrument set for your plant scale.
What is KU viscosity and how is it measured?
KU (Krebs Units) is measured using a KU viscometer (Krebs-Stormer). Target for interior emulsion: 90–110 KU at 25°C. Exterior: 100–120 KU. Always measure at 25°C — viscosity changes with temperature.
What is fineness of grind and why does it matter?
Fineness of grind (Hegman gauge, 0–8 scale) measures pigment dispersion quality. Poor fineness causes grit, reduced gloss, colour inconsistency and lower coverage. Interior emulsion: Hegman 4–5. Premium: 5–6.
What is contrast ratio and how is it measured?
Contrast ratio (hiding power/opacity) = reflectance over black / reflectance over white surface. Measured using Leneta hiding power chart and photometer. Target: 95%+ (economy interior) to 98%+ (premium). Low contrast ratio = poor coverage.
How do I set up in-process QC checkpoints?
After HSD dispersion: check fineness of grind (FOG). After let-down: check viscosity (KU) and pH. Pre-packing: check SG/weight per litre and colour vs swatch. After 24 hours: check dry time. IPCS designs the in-process QC schedule.
What causes viscosity variation between batches?
Thickener lot variation (HEC viscosity grade changes), water quality variation, temperature variation, raw material dosing error, incorrect mixing sequence or time. IPCS root cause analysis covers all common viscosity issues.
What is the scrub resistance test for paint?
Scrub resistance measures the number of wet brush strokes a paint film can withstand before failure (per IS 101 Part 5). Economy emulsion: 200+ scrubs. Washable emulsion: 1000+ scrubs. Premium: 3000+ scrubs.
How do I maintain color consistency between batches?
Fix TiO2 grade and supplier, fix calcium carbonate particle size, use standardized colorant addition procedure, compare against approved standard swatch colorimetrically and keep batch records for traceability.
Does IPCS provide QC training for production staff?
Yes — hands-on QC training as part of plant setup: instrument calibration, parameter measurement, batch record completion, accept/reject criteria and basic troubleshooting. Training is at your factory on your specific instruments.
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