Why Do Swirls Appear in Epoxy Resin?

Swirls or streaks in cured epoxy resin can compromise the clarity and consistency of your project’s finish. These patterns often appear due to mixing issues, additives, air bubbles, or environmental factors. Here's what causes them—and how to prevent them.

🌀 Improper Mixing

• Incomplete or uneven mixing of resin and hardener can lead to streaks, soft patches, or swirls.
• Unmixed portions may cure differently, creating visual inconsistencies.
• ✅ Mix for 3–5 minutes, scraping the sides and bottom of your container.
• ✅ Consider a double-mix method: pour into a second cup and mix again.

🫧 Air Bubbles Introduced During Mixing or Pouring

• Bubbles can trap light and reflect inconsistently, giving the illusion of swirls.
• Fast or aggressive mixing and high pour heights often increase air entrapment.
• ✅ Stir slowly and gently.
• ✅ Pour from a low height or along the side of the mold or surface.
• ✅ Use a heat gun or torch to remove bubbles after pouring.

🎨 Incompatible or Poorly Mixed Additives

• Pigments, dyes, or powders that aren’t designed for epoxy use may not fully disperse, leaving streaks.
• Some additives may clump, float, or separate during the cure.
• ✅ Use epoxy-compatible, high-quality pigments.
• ✅ Mix thoroughly until smooth and even coloration is achieved.
• ✅ Test new additives in small batches before full use.

🧼 Poor Surface Preparation

• Contaminants like dust, oil, or moisture can cause uneven curing and color flow.
• These irregularities often appear as smudges, swirls, or cloudy spots.
• ✅ Clean surfaces thoroughly with isopropyl alcohol.
• ✅ Ensure the substrate is dry and dust-free before pouring.

🌡️ Temperature & Humidity Imbalance

• Too hot, too cold, or too humid conditions can lead to uneven curing or inconsistent pigment behavior.
• These variations may result in visible waves, swirls, or separation of the resin and additives.
• ✅ Work within the resin’s recommended temperature range (typically 18–25°C or 65–77°F).
• ✅ Keep humidity levels below 60% for best clarity and flow.

📌 Final Tips to Avoid Swirls

• Always follow these best practices:
  ✅ Use accurate mix ratios and techniques
  ✅ Mix additives fully and carefully
  ✅ Prepare surfaces properly
  ✅ Work in stable environmental conditions
• When in doubt, test your pigment or design in a small piece first.