Learn how to remove bubbles from cured resin coasters with sanding, filling, flood coats, and beginner-friendly repair steps for clear, glossy handmade coasters.
Learn how to remove bubbles from cured resin coasters with sanding, filling, flood coats, and beginner-friendly repair steps for clear, glossy handmade coasters.
Finding bubbles after your resin coasters have cured is frustrating, especially when the color, shape, and shine looked perfect while the resin was wet. Maybe you noticed tiny pinholes on the surface, a few cloudy pockets near dried flowers, or one large bubble sitting right where the coaster catches the light. The good news is that many surface bubbles can be repaired at home.
This guide explains how to remove bubbles from cured resin coasters without starting over. You will learn how to tell which bubbles are fixable, which supplies make repairs easier, how to sand and fill bubble holes, and when a thin clear flood coat is the cleanest solution. If you are still learning the basics, start with our Resin Art for Beginners guide first, then use this tutorial when a cured coaster needs rescue.
How to Remove Bubbles from Cured Resin Coasters: First Check the Bubble Type
Before you sand anything, look closely at the coaster in bright indirect light. The best repair method depends on where the bubble sits.
Surface bubbles look like small pinholes, craters, or open pits on the top of the coaster. These are the easiest to fix because you can sand the area and fill it with a small amount of fresh resin.
Edge bubbles appear along the side wall or rim of the coaster. They are usually fixable with careful sanding, a detail brush, and a small clear resin fill.
Internal bubbles are trapped inside the cured resin. If the surface above them is smooth and sealed, you usually cannot remove them completely without grinding deep into the coaster. In that case, the goal is to make them less noticeable with a glossy top coat, extra design details, or a creative salvage plan.
Cloudy bubble clusters often appear around flowers, shells, glitter piles, or paper inclusions. These may be a mix of trapped air and moisture. You can improve the surface, but deep cloudy areas may remain visible.
If you want to prevent the issue on your next pour, pair this repair guide with How to Make Resin Coasters Without Bubbles. Prevention is easier than repair, but repair is still worth trying.
Supplies for Fixing Bubbles in Cured Resin Coasters
You do not need a professional studio to repair most coaster bubbles. A small, controlled setup is better than a large messy one.
Useful supplies include:
- Wet/dry sandpaper in 400, 600, 1000, and 2000 grit: $6-$12
- Clear art epoxy resin or UV resin: $8-$35 depending on size
- Nitrile gloves: $8-$12 per box
- Isopropyl alcohol and lint-free cloths: $5-$10
- Toothpicks, silicone detail sticks, or small craft brushes: $3-$8
- Painter's tape: $4-$7
- Craft heat gun or embossing tool: $15-$30
- Plastic drop cloth or silicone mat: $6-$20
- Polishing compound for resin or plastic: $8-$18
- Cork backing or silicone feet if the original backing is removed: $5-$10
For most beginners, the best repair product is either a small batch of the same two-part epoxy used for the coaster or a clear UV resin pen. Two-part epoxy blends well when you are coating the entire top. UV resin is helpful for filling tiny pits because it cures quickly under a UV lamp, but it may yellow faster than high-quality epoxy if the coaster sits in direct sun.
Clean and mark the problem areas
A clean coaster is easier to repair and easier to inspect. Wash the coaster with mild dish soap and water, dry it fully, then wipe the top with isopropyl alcohol. Let the alcohol evaporate before sanding or adding resin.
Hold the coaster at an angle under a lamp and circle the bubble areas with small pieces of painter's tape on the underside or near the edge. Avoid writing directly on the resin surface. Marking the flaws helps you avoid over-sanding the entire coaster when only two or three small spots need attention.
If the coaster has cork backing, felt pads, or rubber feet, remove them before wet sanding. Water can loosen adhesive, and sanding dust can collect around the backing. You can replace the backing after the repair cures.
Method 1: Fill Tiny Surface Bubbles with Clear Resin
Tiny open pinholes are the simplest repair. This method works best when the surrounding surface is already smooth and glossy.
With two-part epoxy, cover the coaster with a clean box while it cures so dust does not land in the repair. With UV resin, cure in short passes and avoid overheating the spot.
After curing, run a fingertip gently across the repair. If the spot feels raised, wet sand with 1000 grit, then 2000 grit, and polish. If the fill shrank below the surface, add a second tiny drop.
This repair is nearly invisible on clear or lightly colored coasters. On dark, metallic, or highly reflective coasters, you may still see a faint outline from certain angles, but it will look much cleaner than an open bubble crater.
Method 2: Sand and Add a Thin Flood Coat
If your coaster has several surface bubbles, scattered craters, dull areas, or scratches, a full flood coat is usually better than spot filling. A flood coat is a thin layer of fresh clear resin poured over the cured coaster to create a new glossy top.
Start by wet sanding the top surface with 400 or 600 grit sandpaper. The goal is not to remove a lot of resin. You only need to dull the shine so the new layer can grip. Sand evenly across the entire top, including the bubble areas, then rinse and dry thoroughly.
Next, tape the underside edge of the coaster if you want to control drips. Place the coaster on small risers over a protected surface. Mix a small amount of clear epoxy slowly and carefully. For a standard 4-inch coaster, you may only need about half an ounce to one ounce of mixed resin for a thin top coat.
Pour the resin into the center and guide it toward the edges with a gloved finger, silicone stick, or disposable brush. Use just enough to cover the surface. Too much resin can dome heavily, run over the sides, or make the coaster uneven.
After pouring, use a heat gun lightly to pop surface bubbles. Keep the heat moving and do not overheat the coaster. Cover and cure for the full time listed on your resin label.
A flood coat is especially helpful for coasters with metallic mica, ocean designs, alcohol ink effects, or glitter because the new clear layer restores depth and shine. For more repair options beyond bubbles, our Resin Art Troubleshooting Guide covers sticky spots, cloudiness, dimples, and curing problems.
Method 3: Repair edge bubbles and rim holes
Edge bubbles are common in coaster molds because air clings to the vertical silicone walls. Once cured, they can look like little chips or holes around the rim.
First, sand the edge lightly with 600 grit wet/dry sandpaper. Keep the coaster wet while sanding to reduce dust and avoid heat buildup. If the bubble left a sharp rim, smooth it until the edge feels comfortable in your hand.
For small holes, apply clear resin with a toothpick or detail brush. Rotate the coaster so gravity helps the resin sit in the hole instead of running out. If needed, repair one side at a time and let it cure before moving to the next side.
For several edge bubbles, you can intentionally create a finished rim. Sand the entire edge smooth, then brush on a thin layer of clear resin, metallic paint, or a resin-safe edge pigment. Gold, silver, pearl white, or matte black edges can make a repaired coaster look designed instead of patched.
If the coaster edge is badly damaged, consider turning the piece into a display tile, trinket tray insert, or magnet instead of using it as a drinking coaster.
Can You Remove Deep Internal Bubbles?
Deep internal bubbles are the hardest truth of resin repair. If a bubble is fully trapped under a smooth cured surface, you cannot simply pop it. To remove it completely, you would have to sand or grind down to the bubble, fill the cavity, and rebuild the surface. On a thin coaster, that can distort the shape or expose embedded decorations.
Instead, choose one of these options:
- Add a clear flood coat to increase shine and reduce how obvious the bubble looks.
- Add a small design element over the area, such as mica veining, foil, vinyl, or a painted accent.
- Use the coaster for personal use instead of gifting or selling it.
- Repurpose it as a practice piece for sanding, doming, or edge finishing.
For handmade gifts, a tiny internal bubble is not always a failure. Resin is a hand-poured craft, and small imperfections are common. The key is deciding whether the coaster is structurally sound, smooth to the touch, and safe for everyday use.
Product Recommendations for Coaster Bubble Repairs
For a reliable beginner repair kit, focus on small tools that give you control.
Best sandpaper range: Wet/dry automotive sandpaper from 400 to 2000 grit. Expect to spend $6-$12. Lower grits remove flaws faster, while higher grits prepare the surface for polishing.
Best resin for flood coats: A clear, UV-resistant, self-leveling art epoxy with a 30-45 minute working time. A small kit costs $20-$35 and will repair many coasters.
Best quick pit filler: Clear UV resin with a UV lamp. Starter sets usually cost $12-$25. Use it for tiny pinholes, not large top coats.
Best polishing upgrade: Plastic or resin polishing compound in the $8-$18 range. It helps restore shine after sanding raised repair spots.
Best finishing detail: Cork sheets, cork rounds, or silicone feet for $5-$10. New backing makes a repaired coaster feel finished and protects tables.
If you are building a fuller beginner kit, the Resin Art Essential Tools guide walks through useful supplies without buying every gadget at once.
Mistakes to Avoid When Fixing Resin Bubbles
Do not pour fresh resin over a glossy cured surface without sanding first. The new layer may peel, bead, or separate over time.
Do not use a torch aggressively on a finished coaster. Too much heat can soften the old resin layer, warp thin coasters, scorch alcohol ink, or damage silicone if the coaster is still in the mold.
Do not sand dry resin without protection. Wet sanding keeps dust down, but you should still work in a ventilated area and clean the slurry carefully. If you use power tools, wear a proper respirator.
Do not add too much pigment to a repair coat. A clear coat usually hides repairs better than a colored coat. Heavy pigment can create streaks, soft spots, or a visible patch.
Do not rush the cure. Even a thin repair layer may need 24-72 hours before the coaster is ready for use, depending on your resin brand.
How to Prevent Bubbles in Your Next Coaster Pour
Once you know how to remove bubbles from cured resin coasters, the next goal is fewer repairs. Most bubble prevention comes down to slower prep.
Warm closed resin bottles in a bowl of warm water for 10-15 minutes before mixing. Stir slowly for the full recommended time, scraping the sides and bottom of the cup. Let mixed resin rest for a few minutes before pouring. Pour in thin layers, especially around dried flowers, shells, paper, and glitter. Use a toothpick around the mold edges, then check again during the first 30-45 minutes.
Seal porous decorations before embedding them. Dried flowers, paper, wood, and fabric can release air after the coaster looks finished. A thin coat of clear-drying glue, sealant, or cured resin helps reduce hidden bubbles.
Finally, cover your coasters while they cure. Dust and lint can create tiny surface defects that look like bubbles after sanding or polishing.
FAQ About Removing Bubbles from Cured Resin Coasters
Can you fix bubbles in resin after it cures?
Yes, you can fix many bubbles in resin after it cures if they are open at the surface or near the edge. Sand the area, fill tiny pits with clear resin, or add a thin clear flood coat. Deep internal bubbles are much harder to remove completely.
Should I use epoxy resin or UV resin for bubble repair?
Use two-part epoxy resin for full flood coats and larger repairs because it blends well and levels smoothly. Use UV resin for tiny pinholes or small spot repairs when you want a fast cure. For coasters that get sunlight, choose UV-resistant products whenever possible.
Can I sand resin coasters to remove bubbles?
You can sand resin coasters to open surface bubbles, smooth raised repairs, or prepare for a new top coat. Wet sanding is best because it reduces dust and heat. Start around 400-600 grit for surface prep, then move to 1000-2000 grit before polishing.
Why did my resin coasters get bubbles after curing?
The bubbles were usually present before curing but became easier to see once the resin hardened. Common causes include cold resin, fast stirring, thick pours, trapped air around decorations, unsealed flowers or paper, and bubbles clinging to mold edges.
Are resin coasters with bubbles still usable?
They may be usable if the coaster is fully cured, smooth enough to clean, and not cracked or sticky. Open bubble holes can trap moisture or dirt, so repair surface pits before using the coaster regularly.
Make the Repair Simple and Clean
Learning how to remove bubbles from cured resin coasters gives you a second chance at pieces that looked disappointing at first. Start by identifying whether the bubbles are surface, edge, or internal. Fill tiny pits, sand and flood coat larger problem areas, and polish raised repairs only after the resin is fully cured.
A repaired coaster may not be flawless under a magnifying glass, but it can still be glossy, useful, and gift-worthy. Better yet, each repair teaches you what to adjust next time: warmer resin, slower mixing, thinner layers, sealed decorations, and a careful bubble check before the cure begins.