Resin Art Coasters: Materials, Mixing, Embedding Objects, and Finishing

Resin art coasters are a perfect intermediate project: small enough to experiment, but detailed enough to refine skills in color effects, embedding objects, and pro-level finishing. This guide walks you through materials, correct resin mixing, embedding botanicals and other inclusions, and achieving a glassy, durable finish that resists heat and daily use. We’ll focus on two-part epoxy resin designed for casting shallow pieces (coasters are typically 3–6 mm thick). Always read your resin’s technical data sheet (TDS) for exact ratios, working time, and cure schedule.

What you’ll need

• Resin and hardener: A low-viscosity, UV-stabilized epoxy suited for molds (often 1:1 by volume; some are 2:1). Look for higher heat resistance (at least 120–150°F/49–65°C once fully cured).
• Silicone coaster molds: Round or square, 90–100 mm diameter. Crisp molds yield crisp edges; deep molds allow layering.
• PPE and safety: Nitrile gloves, eye protection, long sleeves, and a respirator rated for organic vapors if ventilation is limited. Work in a well-ventilated area.
• Mixing gear: Graduated mixing cups, stir sticks, silicone spatulas, disposable pipettes, and an accurate scale if mixing by weight.
• Heat source: A small butane torch or heat gun to release bubbles. Keep away from alcohol and paper.
• Surface prep: Level work surface, silicone mat, painter’s tape, and a dust cover (box or tote).
• Embeds and effects: Dried flowers and leaves (fully dried), metallic leaf, glitter, mica powders, crushed glass/stone, pigment pastes, alcohol inks (sparingly), and sealed photos or paper.
• Tools: Tweezers, toothpicks or needles, craft knife, fine mist 91% isopropyl alcohol (for surface bubble release only), binder clips (to hold covers), and optional pressure pot for ultra-clear casts.
• Finishing: Sandpaper (220 to 2000 grit), water for wet sanding, microfiber cloth, polishing compound, doming resin or a flood coat of your base resin, cork or felt feet, and contact adhesive or peel-and-stick backing.

Plan your design

Before mixing resin, decide on:

• Color palette: Limit to 2–3 colors plus a metallic accent for cohesion.
• Layout: Negative space (clear areas) helps highlight embedded objects.
• Layering strategy: For embedded items, plan at least two layers—base color layer, embed layer, and a final clear cap for depth.
• Heat tolerance: Coasters will meet hot mugs; choose a resin with good heat deflection and allow a full cure (often 72 hours to 7 days) before use.

Tip: Test your color intensity and opacity in a small silicone cup or on a spare coaster mold first. Pigments can look darker in the cup than when spread thin.

Prep the workspace and molds

• Level: Use a bubble level on your table; an unlevel surface causes resin to pool and thin.
• Clean: Wipe molds with tape or a lint-free cloth. Avoid solvents that can degrade silicone.
• Temperature: Aim for 70–75°F (21–24°C). Warm resin bottles in a water bath (sealed bags) if needed to reduce viscosity; do not exceed manufacturer guidance.
• Moisture control: High humidity can cause blush or cloudiness. Avoid pouring during very humid conditions.

Mix resin correctly

Correct ratios and thorough mixing are the foundation of a hard, clear finish.

1. Measure accurately: If your resin specifies volume, use graduated cups. If by weight, use a scale. Do not convert volume-only systems to weight unless your manufacturer provides density-based ratios.
2. Combine parts: Pour Part B (hardener) into Part A (resin), or vice versa per instructions. Some manufacturers specify the order.
3. Stir slowly 2–3 minutes: Scrape sides and bottom. Fast stirring introduces bubbles. Fold rather than whip.
4. Double-cup method: Pour the mixture into a fresh cup and stir another 1–2 minutes. This catches unmixed streaks that cause sticky spots.
5. Working time: Know your pot life (often 25–45 minutes). Portion out into smaller cups if mixing multiple colors to extend workable time.
6. De-bubble: Let the mixed resin sit 1–2 minutes. Briefly pass a heat gun over the surface to pop surface bubbles if needed.
7. Color last: Add pigments or mica sparingly (a pea-sized amount per 100–150 ml as a starting point). Over-pigmenting softens the cure.

Common pitfall: Off-ratio mixing leads to tacky or soft coasters. If in doubt, measure again—precision matters more than speed.

Color and special effects

• Mica powders: Produce pearlescent, opaque colors. Mix thoroughly for a uniform shimmer.
• Pigment pastes: Strong, vibrant color with minimal loading. Ideal for solid color bases.
• Alcohol inks: Great for translucent veining and lacing. Use sparingly; too much can interfere with curing. Avoid mixing large percentages directly into resin; apply as surface accents between layers.
• Metallic leaf and glitter: Add in thin layers. Metallic flakes can trap bubbles; tamp with a stick or mist the surface lightly with isopropyl to help bubbles escape, then use heat quickly.
• Ocean/wave effects: Layer a deep teal translucent base, add white paste along “shore,” and push lightly with a heat gun to create cells. Practice first—heat and pigment density control cell formation.

Embedding objects

Embedding elevates coasters from simple pours to art pieces with depth.

• Dryness is essential: Use fully dried botanicals. Press and dry flowers/leaves beforehand using silica gel or a press.
• Seal porous items: Paper, photos, or wood must be sealed (spray acrylic or thin PVA/Mod Podge) to prevent outgassing and stains. Let fully dry.
• Pre-plan placement: Lay out embeds on a dry mold to finalize spacing.
• Prevent float: Embed in stages so items sit suspended rather than sink or float to the surface.

Layering schedule for clean embeds

1. Base layer (1–2 mm): Pour tinted or clear resin into the mold. Torch lightly to remove bubbles. Wait until the resin reaches a soft gel/tacky stage (often 1–3 hours depending on resin).
2. Place embeds: Using tweezers, lay flowers or objects onto the tacky surface. Gently press down with a clean stick to seat them and push out trapped air along edges.
3. Seal layer (thin): Add a very thin clear pour just to cover embedded edges. Torch/heat gun quickly; avoid overheating flowers.
4. Cap layer (to final thickness): After the seal firms, pour the remaining clear or lightly tinted resin to reach 3–6 mm total. Pop bubbles. Cover to keep dust out.

Note: For thicker items, plan three or more thin pours to avoid exotherm and warping.

Pouring: step-by-step

1. Prime the mold: Optional light mist of mold release designed for silicone can improve demolding for complex shapes; avoid oils or sprays not intended for resin.
2. Pour low and slow: From a height of 2–3 inches, thin stream to minimize trapped air.
3. Manage bubbles: First attack surface bubbles with a heat gun or quick torch passes (keep moving, 6–8 inches away). Do not linger or you’ll warp the silicone or scorch resin. Avoid using heat near isopropyl alcohol.
4. Check edges: Run a toothpick along edges and around embeds to release hidden bubbles.
5. Rest and cover: Place a dust cover over the mold. Revisit within 10–15 minutes to pop late-appearing bubbles, then again at 30 minutes if your pot life allows.
6. Cure undisturbed: Follow your resin’s cure timeline. Typical demold is 12–24 hours; full mechanical strength often takes 72 hours; full properties up to 7 days.

Demolding and finishing

• Demold carefully: Flex the silicone mold to release edges, then peel back. If edges are slightly sharp or have a meniscus, you’ll refine them next.
• Edge cleanup: Trim drips with a craft knife once the resin is firm but not rock-hard, or wet-sand after full cure with 400–600 grit, progressing to 1000–2000 for a satin edge.
• Polish: Use a plastic polish or automotive polishing compound with a microfiber cloth to bring edges to a gloss. For faces that picked up matte texture from a worn mold, lightly sand to 2000 grit and apply a thin flood coat of resin for a glass finish.
• Doming/flood coat: Level your surface. Mix a small batch and apply a thin, self-leveling coat to the top, coaxing resin to the edge without dripping. Pop bubbles. Cover and cure.
• Backing: Apply cork/felt feet or full cork circles with peel-and-stick adhesive. This improves grip and protects tabletops.
• Heat performance: Test with a hot mug after full cure. If you see ring impressions, wait longer for full cure or switch to a higher-heat resin for your next batch.

Best practices

• Measure meticulously: Use the right ratio and mix thoroughly, using the double-cup method.
• Work thin, layer smart: Multiple thin pours reduce exotherm, warping, and bubbles.
• Control environment: Stable temperature, low humidity, and a dust cover are non-negotiable.
• Keep it clean: Wipe tools before resin sets; use baby wipes or isopropyl for fresh resin. Cured resin peels from silicone tools.
• Label batches: Note resin brand, ratio, room temp, pigments used, and pour times to refine your process.

Common pitfalls and how to fix them

• Sticky spots or soft areas: Usually off-ratio or unmixed resin. Scrape off soft material, lightly sand, and overcoat with correctly mixed resin. Severe cases may require complete removal and repour.
• Microbubbles around embeds: Pre-seal porous items and press embeds onto a tacky base before capping. Use a needle to vent bubbles and a quick pass of heat.
• Fish-eyes or craters: Caused by contamination (silicone oils, fingerprints). Clean surfaces with isopropyl, avoid oily sprays, and consider a thin adhesion/skim coat.
• Yellowing: All epoxies amber over time; UV-stabilized resins slow this. Use lightfast pigments, store away from sun, and avoid high-heat exposure.
• Matte finish from the mold: Molds degrade. Restore gloss with a flood coat or replace the mold.

Safety and food-contact notes

• Ventilation and PPE: Wear gloves and eye protection; avoid skin contact. Some people are sensitive to amines; a respirator may be appropriate.
• Fire safety: Keep torch use brief and away from alcohol or paper towels. Never torch inside a box; lift the cover first.
• Food contact: Many cured epoxies are considered inert, but only use resins explicitly labeled food-contact safe if needed. Coasters are indirect contact items, but verify manufacturer claims.

Care and maintenance

• Cleaning: Wipe with a damp cloth and mild soap. Avoid abrasive cleaners and dishwasher cycles.
• Heat: Safe for hot mugs once fully cured, but avoid very high heat (e.g., ovenware). Don’t leave in a hot car or direct sun for long periods.
• Storage: Lay flat to prevent bending during post-cure; avoid stacking until fully cured.

Variations and inspiration

• Geode coasters: Layer translucent color bands, add metallic leaf and crushed glass near the “geode edge,” and finish with a gold-painted rim (use acrylic pen after full cure, then seal).
• Terrazzo look: Mix pre-cured, colored resin chips into a clear or tinted base; sand flush and topcoat.
• Minimal botanicals: Clear base with a single pressed leaf or flower, suspended mid-depth, capped with ultra-clear resin for a floating look.
• Marbled monochrome: Two neutrals plus a metallic vein; pull gentle lines with a stick and set with light heat for soft blends.

Quick step checklist

1. Design plan, colors, and embeds decided.
2. Prep level, clean workspace and molds; set temperature.
3. Measure and mix resin accurately; split and tint.
4. Pour thin base; pop bubbles; wait to tack.
5. Place embeds; seal thinly; cap to final thickness.
6. Cure covered; demold carefully.
7. Sand edges; polish; optional flood coat.
8. Add feet/backing; allow full cure before use.

With precise measuring, patient layering, and thoughtful finishing, your resin art coasters will have clarity, depth, and durability that stand up to daily use while showcasing your style. Keep notes, test small variations, and you’ll quickly build a reliable, repeatable workflow for gallery-worthy results.