Bumpiness in Resin: Causes and Fixes for a Smooth Finish

Bumpiness in Resin: Causes and Fixes for a Smooth Finish

Jun 16, 2024

Bumpiness in resin surfaces can be a frustrating issue for resin artists. It reduces the overall aesthetic appeal of their projects and hinders the achievement of a professional finish. If you've ever experienced bumps or uneven texture in your cured epoxy, don't worry – you're not alone. Additionally, consider joining a resin art workshop where you can learn everything there is to know about working with resin and find effective solutions for controlling bumpiness in resin.

But why is it important to address the problem of bumpiness early on? If left unresolved, these bumps can become more visible over time and may require extensive sanding and refinishing to fix. In this blog, we will explore the common causes of bumpiness in resin surfaces and provide you with effective techniques to fix and prevent this issue. By understanding the root causes and using proper techniques, you can save your time and effort in achieving beautifully levelled results every time.

Understanding Resin Surface Levelling

Resin surface levelling is important in getting a smooth and professional finish for your resin projects. It's all about removing any bumps or unevenness on the cured resin surface so that it looks flawless. Doing this properly can make your creations stand out. To level a bumpy resin surface effectively, here are the key things you'll need:

  • Sandpaper: Get different grits – start with a coarse one (around 80-120) to remove big bumps, then switch to finer grits (200-400) for a smoother finish.
  • Sanding blocks: These are great for stability and control while sanding, making sure you apply even pressure.
  • Self-levelling compounds: These products can fill in any low spots or uneven areas on the resin surface, making it more level.

Step-by-Step Guide to Levelling a Bumpy Resin Surface

Here's how you can do it:

  • Sand the Surface: Use the coarse-grit sandpaper to sand the entire resin surface, focusing on the areas with visible bumps or imperfections.
  • Smooth it Out: Gradually switch to finer-grit sandpaper as you continue sanding, which will help eliminate any scratches left by the coarse-grit one.
  • Use a Sanding Block: To keep things even, use a sanding block instead of just your hand. This way, you won't accidentally press too hard in certain areas and create uneven surfaces.
  • Clean Up: After sanding, wipe away any dust or debris from the resin surface using a clean cloth or compressed air.
  • Apply Self-Levelling Compound (If Needed): If there are still some noticeable low spots or uneven areas, you can use the self-levelling compound to fix them. Just follow the steps recommended by the manufacturer and spread it evenly on the surface.
  • Let It Cure: Give enough time for the self-levelling compound to fully cure before adding resin layers or finishing touches.

Common Causes of Bumpiness in Resin

Improper Mixing

Improper mixing technique is a common culprit behind resin bumpiness. When resin and hardener are not mixed thoroughly or at the correct ratio, it can lead to uneven texture and curing. This results in visible bumps on the resin surface, compromising the overall finish of your project.

One example of improper mixing causing resin bumpiness is when the two components are not blended evenly. This can happen if the mixing process is rushed or if there's inconsistency in the mixing motion. As a result, areas with unmixed or partially mixed resin may cure differently, leading to irregularities on the surface.

Another scenario is when incorrect measurements of resin and hardener are used. Deviating from the recommended ratio can disrupt the chemical reaction between the components, affecting the curing process and resulting in a bumpy finish.

To prevent bumpiness caused by improper mixing, it's essential to follow precise measurement guidelines and allocate sufficient time for thorough mixing. A consistent and thorough mixing technique will help ensure a smooth and uniform resin application.

Inadequate Bubble Removal

Resin bumpiness and surface imperfections can also be attributed to inadequate bubble removal during the resin-curing process. Trapped air bubbles in the resin mixture can lead to irregularities on the surface, causing bumps and an uneven texture. It is essential to address this issue in order to achieve a smooth and flawless resin finish.

Remember that proper bubble removal is an ongoing process throughout each resin curing stage. Regularly inspect your project for any new bubbles that may appear during the curing period and address them promptly.

Other Factors Affecting Resin Smoothness

Resin bumpiness and surface imperfections can also be influenced by other factors besides inadequate bubble removal. Some of these additional elements that contribute to resin surface irregularities include:

  • Environmental Conditions: Fluctuations in temperature and humidity during the curing process can impact the resin's ability to level out smoothly, potentially leading to bumps or uneven areas on the surface.
  • Improper Demoulding Techniques: Rushing the demoulding process or using improper demoulding agents can disrupt the resin's surface, causing it to develop bumps or imperfections.

By being mindful of these factors, crafters can take preventive measures to minimise their impact on the outcome of their resin projects.

Preventive Measures to Avoid Bumpiness in Resin

Preventing resin bumps and avoiding surface imperfections is crucial for maintaining a smooth and professional finish in your resin projects. Implementing key preventive techniques throughout the resin crafting process can effectively reduce the chances of encountering bumpy surfaces. Here are some important measures to consider:

Proper Mixing Methods

One of the main causes of bumpiness in resin is improper mixing. Following the manufacturer's instructions for mixing ratios and techniques is essential to ensure a smooth texture. Use a measuring scale to accurately measure the resin and hardener, and mix thoroughly for the recommended amount of time. Consider using a separate container for each batch to avoid cross-contamination.

Working in a Dust-Free Environment

Dust particles can easily settle on wet resin surfaces, causing imperfections when cured. To minimise this issue, work in a clean and dust-free area. Keep your workspace covered when not in use, and use lint-free wipes or compressed air to remove any dust particles before pouring the resin.

Bubble Elimination Techniques

Trapped air bubbles can also contribute to uneven surfaces in resin. To prevent this, it is important to use effective bubble elimination techniques. After pouring the resin, gently pass a heat gun or torch on the artwork's surface to release any trapped bubbles. Be careful not to overheat or burn the resin.

Proper Demoulding Techniques

Improper demoulding techniques can lead to surface irregularities in the cured resin. When removing your project from the mould, take your time and use gentle pressure to avoid damage or distortion. If necessary, use release agents or mould conditioners to facilitate easy demoulding.


While achieving a perfectly smooth resin surface may require trial and error, following these tips can significantly improve your results. Maintain a clean environment to minimise dust particles, employ effective bubble elimination techniques, and carefully de-mould your projects. You can create stunning, beautiful, flawless resin pieces with time and attention to detail. Incorporating these preventive measures into your resin crafting process can increase your chances of achieving smooth and flawless results. To further enhance your knowledge and skills in resin arts and crafts, Contact Us on Arts Shala for comprehensive guidance on various aspects of resin art, including managing resin thickness.
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