Why do swirls appear in epoxy resin?

Swirls or streaks can appear in epoxy resin for several reasons. Here are a few possible causes:  Improper mixing: Inadequate or improper mixing of the epoxy resin and hardener can lead to swirls or streaks in the finished product. It’s essential to mix the components thoroughly, scraping the sides and bottom of the mixing container, to ensure a homogeneous mixture. Incomplete mixing can result in inconsistent curing and visible variations in the resin.  Incorporating air bubbles : When mixing or pouring epoxy resin, air bubbles can become trapped in the mixture. These bubbles can create swirls or streaks in the resin as it cures. To minimize the appearance of bubbles, ensure that you mix the resin and hardener gently to avoid excessive agitation. Additionally, you can use techniques like slowly pouring the resin and using a heat gun or torch to remove air bubbles.  Using incompatible additives: If you are adding pigments, dyes, or other additives to your epoxy resin, using incompatible or low-quality additives can cause swirls or streaks. Some additives may not fully disperse in the resin, leading to uneven coloring and streaking. It’s important to use high-quality, epoxy-compatible additives and thoroughly mix them into the resin to avoid this issue.  Insufficient surface preparation : The surface to which epoxy resin is applied should be clean, dry, and free from any contaminants. If the surface is not adequately prepared, such as having dust, oils, or moisture present, it can cause swirls or streaks in the resin as it cures. Proper surface preparation, including thorough cleaning and ensuring a dry surface, helps promote a smooth and even application.  Temperature and humidity : Environmental factors such as temperature and humidity can affect the behavior of epoxy resin. Working in high humidity or extreme temperatures can lead to inconsistent curing, which may result in swirls or streaks in the resin. It’s important to follow the manufacturer’s recommendations regarding the ideal temperature and humidity conditions for working with epoxy resin.  By taking care to mix the resin properly, minimize the introduction of air bubbles, use compatible additives, prepare the surface adequately, and consider environmental factors, you can reduce the occurrence of swirls or streaks in your epoxy resin projects. Download PDF here