Eco resin pigment selection is the decision that shapes everything downstream: the technique you can use, the colour stability after cure, and how much the finish changes once you apply a sealer. Get it right at the mixing stage and the rest of the process is predictable. Get it wrong and no amount of swirling or sealing fixes it.
I'm Anirudh, founder of Artriso. This guide covers every pigment type that works reliably in CALSO ONE, the ratios for each, the mixing sequence that prevents uneven colour, and the five colouring mistakes we see most from workshop students and first-time buyers.
If you are still getting to grips with the base material, the mixing ratios guide covers the 3:1 powder-to-water ratio and consistency before you add colour.
The three pigment types that work in CALSO ONE
CALSO ONE is a water-based mineral-acrylic system. It is compatible with water-dispersible pigments, inorganic oxide powders, and mica powders. It is not compatible with oil-based pigments, alcohol inks, or acrylic paint in large quantities.
Oxide pigments are inorganic mineral powders: iron oxide black, red oxide, yellow ochre, umber, raw sienna, and similar earth tones. These are the most reliable pigments in CALSO ONE. They are chemically stable, UV-resistant, and do not affect cure time or pot life at normal working concentrations. The colours they produce are earthy, saturated, and consistent batch to batch. Oxide pigments are the correct choice for any piece where colour repeatability matters, such as production runs, matched sets, or gifting collections.
Mica powders are synthetic mineral particles with a reflective surface. They produce shimmer, pearl, and metallic effects rather than flat solid colour. Gold mica on an Off White base, silver mica on a dark base mixed with black oxide, and copper mica in terrazzo chips are all commercially popular in Indian studio work. Mica powders are compatible with CALSO ONE but slightly more concentration-dependent than oxides: too little and the shimmer reads as barely visible, too much and the surface becomes grainy after cure.
Water-dispersible craft pigments and tints (liquid concentrates sold for ceramics, concrete, or plaster use) work in CALSO ONE provided they are water-based. These are useful for achieving colours that oxide powders cannot: bright blues, greens, purples, and clean whites beyond the Off White base. Test any new liquid pigment on a small sample batch first, as some liquid concentrates extend the pot life or affect surface hardness at high concentrations.
Pigment ratios
The ratio you use determines whether the colour reads as a tint, a solid, or an oversaturated paste. The working ranges below are based on dry pigment weight as a percentage of CALSO ONE powder weight.
For oxide pigments: 1 to 5 percent by weight. At 1 to 2 percent, the result is a soft tint that reads as naturally tinted stone. At 3 to 4 percent, a solid, saturated colour. At 5 percent, a very deep, dense colour that photographs as nearly opaque. Beyond 5 percent, additional oxide does not deepen the colour further and begins to weaken the cure by displacing binder.
For mica powders: 2 to 6 percent by weight. Mica particles are translucent, so a higher loading is needed for the same visual impact as an equivalent oxide dose. At 2 to 3 percent, a subtle shimmer on the base colour. At 5 to 6 percent, a strong metallic or pearl effect.
For liquid concentrates: start at 1 to 2 percent of total mixed weight and adjust upward. Liquid pigments vary in concentration between brands, so the working range here requires testing on your specific product.
For marbling and terrazzo chip batches where you want a concentrated chip or streak colour, push oxide ratios to 4 to 5 percent. The higher concentration ensures the chip or vein colour stays visible against the base after sanding.
Mixing sequence
The order in which you combine pigment, powder, and water matters. The wrong sequence produces streaky, uneven colour that does not fully disperse by the time the material starts to set.
Correct sequence. Add pigment to the dry CALSO ONE powder first and mix them together dry before adding any water. This coats the powder particles with pigment before the acrylic binder activates, which gives even dispersion throughout the slurry. Then add water and mix to the normal slurry consistency.
Why this matters. If you add pigment to the mixed wet slurry, the pigment clumps in the areas where water is already activating the binder. You get streaks of concentrated colour surrounded by pale areas rather than an even tint. The clumping is most visible in light tints where uneven dispersion is obvious after cure.
For mica powders specifically, dry pre-mixing is even more important. Mica flakes tend to float on the surface of wet slurry and need to be encapsulated in the powder mix before water is added to disperse evenly.
Colour combinations that work in Indian studio contexts
A few combinations that come up repeatedly in our workshops and are commercially reliable:
Obsidian black oxide at 3 percent in Off White base produces a deep charcoal that photographs as a true dark grey-stone. Clean, minimal, works across most retail aesthetics.
Umber brown at 2 percent plus red oxide at 1 percent in Off White produces a warm terracotta-adjacent tone. Strong in the Indian gifting market against white and natural linen backgrounds.
No pigment in Brilliant White base produces the cleanest white available. Useful for terrazzo bases where maximum chip contrast is needed.
Gold mica at 4 percent in Off White produces a warm champagne shimmer. One of the top-selling colour combinations from Artriso retail batches.
Black oxide at 4 percent as a base for terrazzo chips, combined with an Off White poured base, produces the classic Milano terrazzo look that has been the dominant studio aesthetic in India for the past two years.
Five colouring mistakes
Adding too much pigment. Above the working range, oxides weaken the cure and mica makes the surface powdery after demould. More pigment does not mean more colour beyond a threshold. If the colour after cure is not dark enough, the issue is usually in the sealing step, not the pigment ratio.
Adding pigment to wet slurry. Covered above. Always pre-mix dry.
Using oil-based pigments. Oil pigments do not disperse in a water-based system. They produce oily streaks, can prevent cure in the affected areas, and may bleed to the surface over time. Check the pigment base before you buy.
Using acrylic paint as a pigment. Acrylic paint works in very small quantities but is mostly water and binder, not pigment. You need large volumes to achieve colour that oxide powders achieve at 2 to 3 grams. At the volumes needed for real colour, the added water throws off the 3:1 ratio and produces a weaker, slower-curing cast.
Expecting sealed colour to match raw colour. The sealer step changes how colour reads. A gloss sealer deepens and saturates colour significantly. A piece that looks pale before sealing often reads as a rich, finished colour after two coats of GlazeSeal. Always seal a sample before adjusting pigment ratios upward.
The colour interaction with technique is covered in the marbling guide and the terrazzo guide. Both have specific pigment recommendations for those techniques.
The complete CALSO ONE range, including base colours and pigment sets, is in the CALSO ONE collection.
Frequently asked questions
Can I use any craft pigment in CALSO ONE?
Water-based pigments, oxide mineral powders, and mica powders are all compatible. Oil-based pigments, alcohol inks, and solvent-based tints are not. Acrylic paint works in very small quantities but is not efficient as a pigment source. When using a new liquid pigment brand for the first time, test on a 100 to 200 gram sample batch before committing to a production run.
How much pigment do I need for a solid, opaque colour?
For oxide pigments, 3 to 4 percent of the dry powder weight gives a solid, saturated colour in most tones. For very deep colours like black or dark umber, 4 to 5 percent. For mica powders, 4 to 5 percent for a strong metallic or pearl effect. Mix dry into the powder before adding water for the most even result.
Why does my eco resin colour look different before and after sealing?
A gloss sealer increases light refraction from the surface, which makes pigment colours appear deeper and more saturated after sealing than before. This is normal and usually an improvement. Test the sealed colour on a sample piece before deciding that your pigment ratio is wrong. A piece that looks pale in the raw matte state often reads as the correct colour after two coats of a gloss sealer.
Do eco resin colours fade over time?
Oxide mineral pigments are UV-stable and do not fade under normal indoor conditions or indirect sunlight. Mica powders are similarly stable. Some liquid craft pigments are less UV-stable, which matters for pieces displayed near windows or used outdoors. If fade resistance matters for your product range, use oxide pigments for base colours and reserve mica for accent effects.
Anirudh Rapole is the founder of Artriso, the Hyderabad studio behind CALSO ONE. Pigment questions? Email contact@artriso.com.
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