How to Colour Jesmonite®: Pigments, Tips & Effects

Which pigments to use with Jesmonite®

The easiest way to colour Jesmonite® is with our liquid pigments, concentrated, water-based colour that stirs in cleanly, stays lightfast and gives consistent results. Because they are so concentrated, a little goes a long way, which makes them very economical over time. (The neon pigments are the exception: those come as a powder.)

You can browse the full range in the Jesmonite® pigments category. Multisets are a smart starting point: they let you experiment across several shades and mix your own custom colours without buying a lot of large bottles. Natural and classic six-colour strips cover most makers’ needs, and you can always add single colours you use often.

You are not limited to our own pigments, either. Any water-based pigment will work with Jesmonite®. Just avoid oil-based colours, solvent dyes or food colouring, which can bleed, fade or interfere with curing.

How much pigment do you need

Not much. Pigments are strong, so you only need a small percentage of your total mix. The rule is simple: add up to about 2% of the total mix weight in pigment, every time. Go beyond that and it can affect how the cast sets. Start with a tiny amount, mix fully, and add more only if you want a deeper colour, it is always easier to build up than to dial back.

A reliable method is to mix your Jesmonite® base powder and Jesmonite® liquid first at the correct ratio (AC100 is 1:2.5, liquid to base; AC84 and AC730 are 1:5), then add the pigment once you have a smooth blend. Stir until the colour is even, with no streaks or dry specks. If you want to repeat a colour later, weigh your pigment and note it down so you can match the shade batch after batch.

Keep in mind that Jesmonite® dries slightly lighter than it looks when wet, and colours can shift a touch as the cast cures over the first day. For anything where matching matters, cast a small test piece first.

Solid colours

Solid, even colour is the foundation, and it is the easiest place to start.

1. Weigh out your Jesmonite® base powder and Jesmonite® liquid to the correct ratio (1:2.5, liquid to base, for AC100).
2. Combine them and mix to a smooth, lump-free consistency.
3. Add up to 2% pigment and stir thoroughly until the colour is uniform.
4. Pour into your mould, tap gently to release air bubbles, and leave to set.

Because Jesmonite® AC100 gives you a comfortable working window of about 10 to 15 minutes (a little less if the room is above 25 °C), demoulds after about 30 minutes and is fully cured after 24 hours, you have a relaxed, forgiving window to work in. That makes it a great choice for beginners chasing clean pastels and confident block colours. For soft tints use very little pigment; for rich shades add more gradually, staying under 2%.

Marble and swirl effects

Marbling looks far more advanced than it is, and the trick is always the same: do not over-mix. How you add the colour depends on which colourant you use.

• With liquid pigments: simply add a few drops of pigment straight into your mix, then swirl it through with a stirring stick just two or three times. The less you stir, the more defined the veins.
• With neon pigments (powder): mix a small, separate batch in the neon colour first, then fold it through your base mix a couple of times before pouring.
• With mica powders: stir the mica into a little Jesmonite® liquid first to make a smooth paste, then swirl that through your Jesmonite® mix.

Pour into the mould and let the veins settle naturally. For a swirl finish, drizzle two or three colours into the mould in ribbons and give it a single gentle twist. Every pour is slightly different, which is part of the charm.

Colour blocking

Colour blocking gives you crisp bands of colour in a single piece. The method is all about timing.

1. Mix and pour your first colour as one layer.
2. Let it firm up for a short while, so it is set enough that the next colour will not blend into it.
3. Mix your second colour and pour it on top.
4. Repeat for as many layers as you like, then leave to set fully.

Tilt the mould slightly between layers for diagonal blocks, or keep it level for clean horizontal bands.

Broken-and-rejoined casts

This technique gives a striking two-tone or two-texture piece with a natural break line. It sounds bold, but it is surprisingly forgiving.

1. Cast your first colour in the mould, a bowl or dish works well.
2. After about 20 minutes, take it out and break the piece in two.
3. Place the pieces back into the mould, leaving a gap.
4. Mix a second batch and pour it into the gap, right up against the broken edges.

The second pour can be a completely different finish, a contrasting solid colour, or even a terrazzo mix, so the two halves read as one deliberate design. Once demoulded, a light sand blends the join.

Terrazzo-style effects

Terrazzo is one of the most popular looks in decorative casting: a speckled surface made from small chips set into a contrasting base. The classic way to make it uses Jesmonite® chips you make yourself.

1. Mix a small amount of Jesmonite®, add a little liquid pigment if you want coloured chips, and spread it in a thin layer on a silicone mat, plastic sheet or paper.
2. Leave it to dry for about 20 to 30 minutes, then break the sheet into small chips.
3. Fold the chips into a fresh Jesmonite® mix (again with liquid pigment if you want a coloured base) and pour into your mould.

As soon as you have demoulded, while the cast is still relatively soft, sand the surface back so the chips show through. Once the piece is fully cured, add a sealer, this brings the colours back out and gives a smooth, professional finish. For the full method, see our dedicated Jesmonite® terrazzo effect guide.

Prefer a ready-made option? StoneRoxx (granite pieces) and GlassRoxx (recycled-glass granulate coloured with water-based pigments) are fun, slightly more natural alternatives that fold into your mix the same way, no chip-making required.

Neon and metallic finishes

When you want colour to really pop, reach for neon pigments (these come as a powder). They work perfectly with AC100 and can also be used with AC84, giving bright, high-impact shades that suit trinket trays, coasters and playful homeware. Neon colours look their best over a white or very pale base, so the pigment has a clean canvas to glow against.

For metallic and pearlescent effects, mix mica-style metallic powders right through your Jesmonite® mix before pouring, for shimmer and sheen all through the cast. Metallic powders are only for adding to the mix, not for dusting onto a finished piece. For a metallic finish on the surface of a cured piece, use awax paste: once your piece is dry, rub it over the surface with a gloved finger, a sponge or a brush, then leave it to dry for about 15 minutes for a lustrous metallic sheen.

Whatever finish you choose, keep to the correct mixing ratio (1:2.5, Jesmonite® liquid to base, for AC100) and add pigment gradually, up to 2% of the mix. Little adjustments make a big difference with these concentrated colours.

Ready to start colouring?

The best way to learn is to mix a few small test casts and see how the colours behave. Explore the full pigments range to find your palette, then try terrazzo with your own Jesmonite® chips (or StoneRoxx and GlassRoxx as a ready-made alternative). With a little practice, you will be turning plain casts into pieces you are proud to display.