How to Seal Resin Moulds for a Flawless Finish Every Time?

Resin moulds are essential for crafting and DIY projects, allowing you to create beautiful, complex designs. Whether making jewellery, home decor items, or art pieces, resin moulds allow you to bring your creative vision to life. However, achieving a flawless finish with resin can be challenging, as imperfections and air bubbles can affect the final result.

That's where sealing resin moulds becomes crucial. Properly sealing your moulds ensures that your castings are perfect every time, without any imperfections or trapped air bubbles. Sealing the moulds creates a barrier that prevents resin from leaking out and ensures a smooth and professional-looking finish.

If you're new to working with resin or want to improve your skills, joining a resin art workshop can provide hands-on experience and guidance from experts. In this blog, we'll walk you through the step-by-step process of sealing resin moulds for a flawless finish. By following these techniques, you'll be able to achieve professional-looking results and take your resin art to the next level.

Materials Needed for Sealing Resin Moulds

Before you start sealing your resin moulds, make sure you have these materials on hand:

• Release Agent Spray: This is crucial for easy demoulding once the resin is fully cured. It forms a protective layer between the mould and the resin, making releasing the cured piece without damage easier.
• High-Quality Silicone Sealant: Look for a silicone sealant for mould-making and casting. It should be firm, able to handle heat, and compatible with your resin type.
• Mixing Cups: Disposable plastic or silicone cups are best for accurately measuring and mixing resin and silicone sealant. Look for cups with clear volume markings to ensure precise measurements.
• Stirring Sticks: You'll need wooden or plastic sticks to thoroughly mix the silicone sealant before applying it. Ensure they're long enough to reach the bottom of your mixing cups without causing any splashing.
• Protective Gear: Safety should always be a priority when working with chemicals. Wear gloves to shield your hands from direct contact with the sealant, safety goggles to protect your eyes, and a mask to prevent inhalation of fumes.

Step 1: Preparing the Mould

When preparing resin moulds for sealing, starting with a clean mould cavity is essential. Here’s how to ensure your mould is free from any contaminants before moving on to the sealing process:

1. Inspect the Mould: Check the mould for any dust, debris, or residue from previous castings. It's crucial to start with a clean surface to achieve a flawless finish.
2. Cleaning Process: Moisten the lint-free cloth or brush with denatured alcohol and gently wipe the entire mould cavity, thoroughly cleaning all surfaces. Pay close attention to any crevices or intricate details within the mould.
3. Importance of Cleaning: Properly cleaning the mould cavity is crucial, as any leftover residue or particles can affect the adhesion and effectiveness of the silicone sealant.

Applying Silicone to the Outer Edges

Before applying the silicone sealant, properly preparing the resin mould is essential. Here's what you need to do:

• Clean the mould cavity thoroughly with denatured alcohol to remove dirt or residue that could affect the sealant's adhesion.
• Ensure the mould is completely dry, with no dust particles on it.
• Apply a silicone fillet along the outer edges of the mould walls and base to create a barrier for the resin later on.

How to Apply Silicone to the Outer Edges?

• Get the silicone ready: Cut the tip of the silicone tube at a 45-degree angle to create a small opening for precise application.
• Put on the silicone: Squeeze a steady line along the outer edges of the mould walls and base, ensuring it covers everything evenly.
• Make it smooth: Use a silicone tool or your gloved finger to spread and smooth out the silicone, ensuring no gaps or uneven spots.

Step 2: Applying Silicone to the Inner Joints

Sealing the inner joints or seams of the mould is crucial to prevent any resin leakage during casting. Here's how you can do it:

• Use a small brush or gloved finger to spread a thin silicone layer along the seams.
• Cover all the inner joints with silicone, filling them up completely.
• Smooth the silicone using your finger or a tool, ensuring no gaps or air pockets are left behind.
• Apply gentle pressure while spreading the silicone to ensure it gets into every corner.
• Use a back-and-forth motion to smooth out any uneven areas.
• Hold the mould up to the light to check for missed spots. If you see any gaps, apply more silicone to fill them in.

Step 3: Curing and Cleaning the Sealed Mould

After applying the silicone sealant to your resin mould for a tight seal, it's essential to let the sealant cure entirely and create a strong barrier inside the mould cavity. This is crucial to prevent resin from leaking or seeping out during casting. Here's what you need to do to ensure proper curing of the sealed mould:

• Curing Time: Typically, the sealant takes 24 to 48 hours to cure and reach its maximum strength fully. Taking time with this step is essential, as removing the mould too early can damage or ruin the castings.
• Cleaning the Mould Cavity: Before you pour the resin into the sealed mould, thoroughly clean the interior surface. Any dust or debris left inside can result in imperfections in your castings. Use compressed air or a lint-free cloth to remove loose particles from the cavity and ensure it's completely clean.

Step 4: Levelling and Clamping the Mould

Ensuring the mould is levelled and securely clamped when working with resin moulds is crucial. This step is essential to prevent uneven resin distribution and potential leaks from one side. Here are some techniques you can use to level and clamp your resin mould effectively:

Levelling the Mould

• Place a level on top of the mould to check if it sits evenly on your work surface.
• If the mould is not level, adjust its position by placing shims or wedges under one side until it is perfectly level.
• Ensure that all sides of the mould are at an equal height to maintain consistent resin flow.

Securing the Mould

• Use adjustable clamps: If your mould has removable sides or walls, use adjustable clamps to hold them firmly in place during the casting process.
• Apply gentle pressure with the clamps to ensure a tight seal and prevent any movement that could disrupt the resin pour.
• If you don't have adjustable clamps, you can keep the mould stable by strategically placing heavy weights around it.

Step 5: Pouring Epoxy into the Sealed Mould

Now that you have correctly sealed and prepared your resin mould, it's time for the final casting step – pouring the epoxy into the mould. This step is crucial in achieving a flawless finish for your project. Here are some key considerations when pouring epoxy into a sealed resin mould:

• Selecting the suitable epoxy resin: Choosing an epoxy resin compatible with your mould material and desired curing time is essential. Various types of epoxy resins are available, such as clear casting or pigmented resins, each with its properties.
• Mixing the epoxy: Follow the manufacturer's instructions to mix the epoxy resin properly. This usually involves combining a resin and hardener in specific ratios and stirring them thoroughly. Don't introduce air bubbles during mixing; they can ruin the final result.
• Pouring technique: Slowly pour the mixed epoxy into the sealed mould, starting from one end and gradually filling it up. Avoid pouring too quickly or forcefully, as this can create turbulence and introduce air bubbles. Use a stir stick or toothpick to guide the epoxy into intricate details or tight corners if needed.
• Removing air bubbles: After pouring the epoxy, you may notice tiny air bubbles rising to the surface. To eliminate these bubbles, you can use a heat gun to pass over the epoxy's surface gently. The heat will cause the bubbles to rise and pop, leaving behind a smooth finish. Be cautious not to apply too much heat or hold it too close to avoid scorching or damaging the resin.

Step 6: Removing Castings from the Sealed Mould

Start by removing any outer walls or containment devices from the sealed mould. This helps prevent accidental damage to the casting or the mould during the demoulding process. Utilise non-destructive release techniques, such as flexing or twisting the mould, to smoothly release the casting without harming the final product or the mould itself.

Conclusion