How to Make Terrazzo Coasters: A Beginner’s Guide

Terrazzo coasters look deceptively simple: colorful chips scattered through a smooth stone-like surface. Yet first-time makers often discover that the quality of the finished coaster depends on a handful of small decisions—accurate measuring, controlled mixing, thoughtful chip placement, proper curing, and patient sanding.

That is also what makes terrazzo coaster making such a good beginner craft. You can learn several useful casting and finishing techniques on a small, manageable object without committing to a large project. Traditional terrazzo achieves its distinctive appearance by embedding decorative aggregates in a cement or resin matrix and finishing the surface to reveal those materials. At craft scale, the same visual idea can be recreated with colored chips embedded in a castable material such as Jesmonite. 

In Singapore, coaster making has also become a practical social craft rather than simply a solo DIY project. Craft Labs, for example, offers both marbling and terrazzo coaster formats as part of its coaster-making workshops, with activities designed for anything from small groups to large corporate events. 

Whether you are making your first set at home or want to understand the process before joining a coaster making workshop in Singapore, this guide walks through the techniques that make the biggest difference.

What You Need Before You Start

You do not need a workshop full of specialist tools to make your first terrazzo coaster. Jesmonite says AC100 does not require specialist equipment for basic casting, although accurate weighing and careful mixing are essential. 

For a straightforward beginner project, prepare:

• Jesmonite AC100 base and liquid, or another casting system designed for this type of craft. Follow the exact ratio specified for your chosen material rather than improvising.
• Jesmonite-compatible pigments in two or three chip colors plus an optional color for the main coaster body. Jesmonite lists AC100 at a 2.5:1 powder-to-liquid ratio by weight. 
• A silicone coaster mold. Flexible silicone molds are commonly recommended because they reproduce detail well and make demolding easier. 
• Digital scales, mixing cups, and a silicone spatula or suitable mixing tool.
• A flat sheet or shallow mold for making terrazzo chips, unless you already have cured offcuts available.
• Sandpaper in several grades. Jesmonite suggests experimenting from coarse 60–80 grit through medium and fine grades up to approximately 320 grit, depending on the finish required. 
• A compatible sealer for the final surface. Jesmonite recommends its Acrylic or Gloss Sealers for AC100. 
• Gloves, a mask for sanding, and a well-ventilated workspace. Jesmonite specifically recommends appropriate gloves, masks, and ventilation when working and finishing its materials. 

One beginner mistake is buying too many pigments. Start with a restricted palette. Two chip colors and one background shade usually look more intentional than six competing colors, and you can always expand your collection later.

How to Make Terrazzo Coasters Step by Step

Create the Terrazzo Chips and Plan Your Color Palette

Begin with the decorative chips because they must already be hard before they are embedded in your coaster.

Mix a small batch of casting material according to the manufacturer’s ratio, divide it between separate cups, and add pigment to each portion. Jesmonite recommends keeping pigment additions controlled; for strong color, its guidance suggests around 2% pigment by total mix weight, while much smaller quantities can produce softer pastel shades. Excess pigment can interfere with setting and weaken a cast, so more colorant does not necessarily mean a better result. 

Spread each color into a thin sheet and allow it to cure. Once hard, break the sheet into irregular fragments.

Avoid making every chip identical. A combination of tiny speckles and a smaller number of medium fragments gives the surface greater visual depth. Jesmonite notes that decorative terrazzo chips can be made as thin as approximately 2 mm, making relatively delicate fragments practical for coaster-sized objects. 

You can also reuse cured leftovers from previous pours instead of discarding them. Jesmonite itself highlights turning cured leftover material into terrazzo chips as a practical reuse method. 

Before mixing your main batch, place a few chips beside your intended base color. This simple test helps prevent a surprisingly common design problem: chips disappearing because their tone is too similar to the background.

Mix, Cast, Cure, Sand, and Seal

Start by measuring accurately. For Jesmonite AC100, use the manufacturer’s 2.5:1 powder-to-liquid ratio by weight. The quantity required depends on your mold, so use its capacity or the manufacturer’s material calculator rather than estimating by eye. 

Add liquid before powder. Jesmonite’s current bubble-prevention guidance recommends placing the liquid in the mixing container first, then adding the powder. Mix steadily rather than whipping the mixture aggressively. Fast, uncontrolled mixing can incorporate air, while excessive mixing gives the material additional opportunity to trap bubbles. 

Once the mixture is smooth, add your cured terrazzo fragments and fold them through gently. You want chips distributed throughout the material rather than sinking into one dense layer.

Pour slowly into the silicone mold. Work the material into corners and edges, then gently tap or vibrate the mold. For particularly clean surfaces, Jesmonite recommends brushing a thin initial layer into the mold or vibrating the first layer so trapped bubbles can escape before the remainder is added. 

Leave the coaster undisturbed until it has set and cooled sufficiently to demold. Jesmonite notes that the material becomes warm during its curing reaction and recommends waiting until it has cooled before removal. Although a cast may feel hard surprisingly quickly, the manufacturer advises allowing approximately 24 hours after demolding before sanding or sealing so the piece can fully cure. 

Then comes the step that transforms a plain speckled casting into a convincing terrazzo surface: sanding.

Begin with enough abrasion to expose the hidden chips without removing excessive material. Once the colors appear evenly across the face, move progressively to finer sandpaper. Do not stay with coarse paper longer than necessary; its purpose is to reveal the pattern, while finer grades refine the surface. Jesmonite confirms that cured AC100 can be sanded from coarse through progressively finer grades to create different finishes. 

Remove every trace of sanding dust before sealing.

Finally, apply a compatible sealer in thin, even coats. Jesmonite recommends multiple thin applications rather than one heavy layer, with acrylic sealer preserving more of the material’s matte appearance while gloss sealer creates a shinier finish. 

One important limitation is worth understanding: Jesmonite states that its materials and sealers have not been tested as food-safe, so do not treat the coaster as a surface for direct food contact. It is intended to sit beneath cups, glasses, or decorative objects rather than function as a serving plate. 

Common Terrazzo Coaster Mistakes and Singapore-Specific Tips

Small casting projects are forgiving, but the same few errors tend to affect the finish. Most can be prevented before you pour.

• Too many bubbles: Add liquid first, mix steadily, pour carefully, and tap or vibrate the mold. Overly aggressive mixing is a known cause of trapped air. 
• Weak or poorly cured pieces: Measure the powder and liquid by weight instead of estimating volumes, and avoid excessive pigment. Correct ratios are fundamental to the material’s performance. 
• Terrazzo chips barely visible: Use stronger contrast between the chips and matrix, and sand enough to expose chips located slightly below the cast surface.
• Scratches after sanding: Do not jump straight from very coarse paper to an ultra-fine grade. Work progressively through intermediate grits. Jesmonite suggests a range from approximately 60–80 grit at the coarse end through 320 grit for ultra-fine finishing. 
• Streaky sealer: Clean and dry the surface completely and apply several thin coats instead of a heavy coat. A sponge can give a particularly even finish on small AC100 objects. 
• The mixture hardens before you finish pouring: Prepare your mold, pigments, tools, and chips before mixing the main batch. Jesmonite’s working and set times are temperature-sensitive, with warmer environments accelerating setting. 

That last point deserves particular attention in Singapore. Meteorological Service Singapore recorded an annual mean temperature of 28.1°C in 2025, and warm conditions are normal locally. Because Jesmonite’s set time changes with temperature, working in a cool indoor space and preparing everything before mixing can make the process considerably easier. 

A guided workshop can therefore be useful for your first attempt. Instead of simultaneously learning ratios, timing, color selection, bubble control, sanding, and sealing through trial and error, you can see the sequence demonstrated before repeating it yourself. Craft Labs currently lists coaster making among its Singapore craft activities and offers participants the choice of marbling or terrazzo coaster styles. 

Want to learn how to create your own terrazzo coasters with expert guidance? CraftLabs workshops provide a hands-on experience where participants learn essential techniques such as material mixing, color selection, chip placement, casting, sanding, and finishing. Whether you are trying this craft for the first time or looking for a creative group activity, CraftLabs helps you understand the process while creating a personalized handmade piece. To join a workshop or learn more, visit www.craftlabs.sg or contact CraftLabs for more details. 

Frequently Asked Questions

What material is best for beginner terrazzo coasters?

A water-based casting material such as Jesmonite AC100 is a practical option for indoor decorative coasters because it accepts pigments, can contain cured chips, reproduces mold detail, and can be sanded after curing. 

How long should terrazzo coasters cure before sanding?

For Jesmonite AC100, allow the demolded piece to cure for about 24 hours before sanding or sealing. Although it may become firm enough to demold earlier, full strength develops later. 

Why are my terrazzo chips not showing?

Most chips sit slightly beneath the cast surface. Sanding removes a thin outer layer and exposes their cross-sections, which is why sanding is a defining part of achieving the terrazzo look. 

Do terrazzo coasters need to be sealed?

Sealing is recommended when improved water and stain resistance is desirable. For AC100, Jesmonite recommends Acrylic or Gloss Sealer, applied to a clean, dry surface.