Eco Resin vs Plaster of Paris: Which Is Right for Your Studio?

Eco resin vs plaster of paris is one of the most common material questions we get from Indian makers who are either starting out or trying to understand why their PoP pieces are not surviving in the market. The honest answer is that they are not competing products. They are different materials with different strengths, and the right choice depends entirely on what you are making and what you need it to do.

I'm Anirudh, founder of Artriso. We make CALSO ONE, so I have an obvious interest here. I'll give you the accurate comparison, including the cases where PoP is the right call.

## What you are comparing

Plaster of Paris is calcium sulphate hemihydrate, a fine white powder that sets when mixed with water. It has been used in India for decorative casting for decades. It is inexpensive, widely available, easy to use, and sets quickly. It is also brittle, highly water-absorbent, and unsuitable for anything that will contact moisture in regular use.

Eco resin (CALSO ONE) is a mineral-acrylic composite: a fine calcium carbonate powder bound by an acrylic polymer that activates on contact with water. It sets at the same 3:1 powder-to-water ratio as PoP and handles similarly at the mixing stage, which is why makers who are familiar with PoP find CALSO ONE an easy transition. The cured material is denser, harder, more flexible, and significantly more water-resistant than plaster.

Strength and durability

This is the most significant difference between the two materials.

Plaster of Paris has a compressive strength of roughly 5 to 8 MPa when fully cured. It is a hard material in the sense that it resists denting, but it is brittle: a sharp impact at an edge or corner chips or cracks it. Coasters, trays, and decorative objects made from PoP break easily if dropped and show edge chips within weeks of regular handling.

CALSO ONE has a compressive strength of approximately 40 to 50 MPa when fully cured: five to eight times higher than PoP. It also has a degree of flexural toughness that plaster lacks, which is what allows thin sections like coaster edges and tray lips to survive daily use without chipping. A cured CALSO ONE coaster dropped on a tile floor from table height will survive in most cases. A PoP coaster will not.

For anything intended for sale or regular functional use, the strength difference is not a minor factor. It determines whether the product survives in the customer's home for a year or shows edge chips within the first month.

Water resistance

Plaster of Paris is hydrophilic: it actively absorbs water. An unsealed PoP coaster left under a wet glass overnight will absorb moisture, weaken at the surface, and begin to show surface erosion with repeated contact. Sealing PoP helps but does not eliminate the problem, because the pore network in cured plaster is extensive and the sealer only treats the surface.

CALSO ONE is water-resistant out of the mould and fully waterproof once sealed. The mineral-acrylic chemistry produces a much denser, less porous material than plaster. An unsealed CALSO ONE coaster handles brief moisture contact without damage. With two coats of a water-based acrylic sealer, it handles sustained moisture exposure without surface degradation. The waterproofing guide covers the sealing detail.

For coasters, trays, planters, or any piece with water contact, this difference is the reason PoP is not suitable for production use.

Finish quality

Plaster of Paris demoulds with a slightly chalky, matte surface. It takes pigment well at low concentrations, accepts paint after cure, and can be sanded to a smooth surface. The natural finish is flat and slightly dusty in character.

CALSO ONE demoulds with a smooth, consistent matte surface that reads as mineral or stone-like rather than chalky. It takes pigment at much higher saturation than PoP before the cure is affected. The demoulded surface has a density and cleanness that plaster cannot match, which is why eco resin pieces photograph and retail differently from painted PoP pieces.

Sealing changes the comparison further. Sealed eco resin reads as a finished product: ceramic-like if gloss-sealed, natural stone if wax-sealed. Sealed PoP still reads as painted plaster.

Cost per piece

This is where the comparison is closest, and where PoP has a genuine advantage for certain uses.

CALSO ONE Off White at the 1 kg pack costs ₹499. For a standard 90 mm round coaster at 8 mm fill depth (approximately 80 grams of mixed material, 60 grams of powder at 3:1), the raw material cost is roughly ₹30 per coaster.

A 1 kg bag of plaster of Paris from a local building supply source in India costs ₹30 to ₹50. The same coaster in PoP uses roughly 80 grams of mixed material (40 grams of powder at 2:1 ratio), which comes to ₹2 to ₹4 in raw material.

The raw material cost gap is real: PoP is ten to fifteen times cheaper per kilogram. However, the comparison changes when you account for the failure rate (PoP pieces break at a far higher rate during demould, sanding, and in use), the cost of returns or replacements if you are selling, and the price premium that finished eco resin pieces command in the Indian retail and gifting market versus PoP pieces.

Studios that have switched from PoP to CALSO ONE consistently report that the per-piece cost increase is more than recovered in the selling price differential and the elimination of breakage and returns.

The full comparison

What each material is right for

Plaster of Paris is the right material for: practice casts and learning mould shapes before committing to more expensive materials, sculptural pieces that are display-only with no water or impact contact, temporary or event installations, children's craft activities where cost per session matters more than durability, and any application where the piece will be painted over entirely and structural strength is not required.

CALSO ONE is the right material for: anything you intend to sell, any functional piece that will contact moisture (coasters, trays, planters), any piece with fine detail edges that need to survive handling, production work where batch consistency matters, and any studio where marbling, terrazzo, or colour-intensive techniques are part of the offer. If your goal is a product that customers are paying for, PoP is not the right substrate.

The full material background, including how CALSO ONE compares to Jesmonite and epoxy resin, is in the complete eco resin guide.

The CALSO ONE collection is the starting point if you are ready to make the switch.

Frequently asked questions

Is plaster of paris stronger than eco resin?

No. CALSO ONE has a compressive strength of 40 to 50 MPa versus 5 to 8 MPa for plaster of Paris. Eco resin is five to eight times stronger and significantly more resistant to chipping, cracking, and edge damage. Plaster feels hard to the touch but is brittle under impact stress. CALSO ONE has both hardness and a degree of toughness that plaster lacks.

Can I seal plaster of paris to make it waterproof like eco resin?

Sealing reduces water absorption in PoP but does not make it waterproof in the way that a sealed eco resin piece is. Plaster has an extensive pore network that runs through the full depth of the material. A surface sealer closes the outer pores but not the internal structure. Repeated moisture contact will eventually cause surface softening and degradation in sealed PoP over time. For pieces that will contact water regularly, eco resin is the correct material.

Is eco resin worth the higher cost compared to plaster of paris?

For practice and learning, PoP is a reasonable starting material because the cost of failed casts is low. For any piece intended for sale or functional use, the cost comparison shifts significantly. CALSO ONE costs more per kilogram but commands a higher retail price, breaks less during production, and does not fail in customer use. The per-piece economics of eco resin are better than PoP once you are selling rather than practising.

Can I use the same moulds for both materials?

Yes. Both plaster of Paris and CALSO ONE are compatible with silicone, polypropylene, and most craft moulds. The demould time differs: PoP typically sets in 20 to 30 minutes at 2:1 ratio, while CALSO ONE demoulds in 45 to 60 minutes at 3:1 for thin pieces. Silicone moulds work well for both. The same mould collection works across the transition from PoP to eco resin.

Anirudh Rapole is the founder of Artriso, the Hyderabad studio behind CALSO ONE. Questions about switching from PoP to eco resin? Email contact@artriso.com.