What Causes Epoxy Resin to Have a Milky or Cloudy Appearance?

If epoxy resin appears milky or cloudy after curing, it is often due to moisture, temperature issues, improper mixing, or trapped air. Below are the most common causes and ways to prevent cloudiness in epoxy resin projects.

💧 Moisture or High Humidity

• Epoxy resin is highly sensitive to moisture during curing.
• Excess humidity or direct exposure to water can cause a hazy, milky appearance.
• Best practices:
  ✅ Work in an environment with low humidity (ideally below 60%).
  ✅ Avoid pouring resin in rainy or extremely humid conditions.
  ✅ Store resin in a dry, sealed container to prevent moisture absorption.

🌀 Improper Mixing

• Incomplete mixing leads to uneven dispersion of components, creating cloudiness.
• Best practices:
  ✅ Stir slowly and thoroughly for at least 3-5 minutes.
  ✅ Scrape the sides and bottom of the mixing container.
  ✅ Use a clean mixing cup to prevent contamination.

❄️ Cold Temperature During Curing

• Low temperatures slow the curing reaction, preventing full cross-linking and causing haziness.
• Best practices:
  ✅ Work in a temperature-controlled room (18–25°C / 65–77°F).
  ✅ Warm resin slightly before mixing if stored in a cold space.
  ✅ If necessary, use a resin curing heat mat to maintain warmth.

🪵 Moisture in the Surface or Substrate

• If the surface being coated contains trapped moisture, it can rise into the resin and create a milky look.
• Best practices:
  ✅ Ensure wood, concrete, or porous materials are completely dry.
  ✅ Apply a sealing coat first before pouring deep layers.

🫧 Trapped Air Bubbles

• Tiny bubbles scatter light, making resin appear hazy.
• Best practices:
  ✅ Stir slowly to minimize bubble formation.
  ✅ Pour resin in thin layers rather than a single thick pour.
  ✅ Use a heat gun or torch to remove surface bubbles.

🎨 Incompatible Additives or Pigments

• Some pigments, glitters, or dyes may react poorly with resin, creating cloudiness.
• Best practices:
  ✅ Use resin-compatible pigments and additives only.
  ✅ Mix thoroughly to ensure even dispersion.
  ✅ Test in a small batch first before full application.

📌 Final Thoughts

• Temperature, humidity, and moisture are the biggest culprits of cloudy resin.
• Mixing properly and degassing bubbles improves clarity.
• Sealing porous surfaces first prevents unexpected clouding.
• Always refer to manufacturer guidelines for product-specific best practices.