Why Dimples and Soft Spots Occur in Epoxy Resin Once Cured

Dimples, tacky patches, or soft spots in cured epoxy resin are often the result of mixing errors, improper curing conditions, or surface contamination. These issues not only affect the appearance but can also compromise the durability and integrity of your project. Here's a breakdown of the most common causes and how to avoid them:

🌀 Incomplete Mixing

• One of the most common causes of soft or tacky areas.
• If the resin and hardener are not thoroughly combined, the chemical reaction cannot complete.
• Best practices:
  ✅ Mix for at least 3–5 minutes, scraping the sides and bottom of the container.
  ✅ Transfer to a second cup and mix again (double-cup method) for extra consistency.

⚖️ Incorrect Resin-to-Hardener Ratio

• Epoxy resin requires precise mixing ratios (e.g., 2:1 or 1:1 by volume).
• Too much or too little hardener disrupts the curing process.
• Best practices:
  ✅ Always use accurate measuring tools.
  ✅ Follow the manufacturer’s recommended ratio exactly.
  ✅ Never “eyeball” measurements.

⏳ Insufficient Curing Time

• Resin needs time to fully cure. Handling or disturbing it too early can cause soft areas.
• Cooler environments may prolong cure time beyond the standard 24–72 hours.
• Best practices:
  ✅ Allow full cure as per instructions — some projects require up to 7 days.
  ✅ Avoid touching or demolding too soon.

🌡️ Environmental Conditions

• Cold temperatures or high humidity can cause curing delays or uneven surfaces.
• Best practices:
  ✅ Work in a temperature-controlled space (ideally 18–25°C).
  ✅ Avoid pouring resin during humid or wet weather.
  ✅ Store materials in the same room prior to use to acclimate.

📏 Excessive Pour Thickness

• Pouring resin too thick can generate excess heat, leading to an uneven cure.
• This may cause dimples, bubbles, or tacky patches in deeper areas.
• Best practices:
  ✅ Follow your resin's recommended maximum pour depth (e.g., 10–20 mm per layer).
  ✅ For deeper projects, pour in layers, allowing each to partially or fully cure.

🧼 Contamination or Moisture

• Dust, oils, or moisture on the surface or in the resin can disrupt curing.
• This often results in localized soft spots or cloudy dimples.
• Best practices:
  ✅ Wipe surfaces clean with isopropyl alcohol before pouring.
  ✅ Work in a dust-free, dry area.
  ✅ Avoid using materials that contain trapped water (e.g., wet wood or paper).

📌 Final Thoughts

• Dimples and soft spots can usually be prevented with:
  ✅ Accurate mixing
  ✅ Clean surfaces
  ✅ Proper temperature & humidity control
  ✅ Respecting recommended cure times and pour depths