Eco Casting Powder vs Plaster of Paris: Which Should You Use?
Both are gypsum-based powders you mix with water and pour into a mould. But they behave very differently once they set. Here's how they compare on strength, cure time, colour and finish, and which one suits your project.
The Quick Answer
Plaster of Paris is a cheap, soft, general-purpose plaster that's fine for school projects and practice casts. Eco casting powder is a gypsum-based casting powder that's stronger than standard plaster of Paris, mixes at 3 parts powder to 1 part water, sets in 30 minutes and is fully cured in 2 hours. For coasters, trinket dishes, candle holders, planters and homewares you want to keep or sell, eco casting powder is the better choice.
| Eco casting powder | Plaster of Paris | |
|---|---|---|
| Base | Gypsum-based, premium 3200 grade | Gypsum-based |
| Strength | Stronger than standard plaster of Paris | Soft and chalky; chips and breaks more easily |
| Mix | 3:1 powder to water by weight | Varies by product; follow the pack |
| Set | 30 minutes, then demould | Sets quickly, but stays damp inside |
| Fully cured | 2 hours | Can take a day or more to dry right through |
| Colour | Mix liquid pigment in before pouring | Usually painted after drying |
| Best for | Plant pots, trays & coasters, terrazzo-effect homewares, candle holders, craft & hobby casting | Kids' crafts, practice casts, quick tests |
What Is Plaster of Paris?
Plaster of Paris is gypsum that has been heated and ground into a fine white powder. Add water and it hardens back into a solid. It's cheap, easy to find and quick to set, which is why it's been a craft and classroom staple for generations.
The trade-off is strength. Plaster of Paris dries soft and chalky, so thin edges chip, corners break and pieces can crumble if they're knocked or handled a lot. It also soaks up water if it isn't sealed, and thicker casts can stay damp inside for a day or more after they look set.
What Is Eco Casting Powder?
Eco casting powder is also gypsum-based, but it's a premium 3200 grade casting powder made to be stronger than standard plaster of Paris. Our SolidCrete Eco Casting Powder mixes at a simple 3:1 ratio of powder to water, sets in 30 minutes and reaches a full cure in 2 hours.
That combination means you can demould quickly, finish pieces the same day and end up with casts that stand up to everyday use, which matters when you're making homewares, gifts or stock for markets.
Which One Should You Choose?
Coasters, trinket dishes, candle holders, planters and terrazzo-effect homewares, especially anything you plan to gift or sell.
Mix liquid pigment straight into the wet mix for colour all the way through, rather than painting the surface afterwards.
Demould at 30 minutes and fully cured at 2 hours, so you can batch pieces in a single session.
Kids' crafts, quick mould tests and pieces that won't be handled much.
How to Cast With Eco Casting Powder
Weigh powder and water at 3:1
Use 3 parts powder to 1 part water by weight. For example, 300g of powder to 100g of water. Weighing on a kitchen scale keeps every batch the same.
Mix until smooth
Stir thoroughly until the mix is an even, uniform consistency with no dry lumps.
Add colour (optional)
Add liquid pigment a drop at a time, building up to around 2–5% by weight of the total mix. Stir until the colour is fully dispersed.
Pour into your mould
Pour into a clean silicone mould. Flexible silicone makes it easy to release the cast without breaking edges.
Demould at 30 minutes, cure for 2 hours
Allow 30 minutes for the initial set before demoulding, then leave the piece for a full 2 hours to cure before handling or finishing.
Seal after 24 hours
Wait at least 24 hours after casting, then seal with one of our varnishes: a gloss varnish for a shiny finish or a matte varnish for a low-sheen finish.
Shop eco casting powder →Project Ideas
Flat, simple shapes that show off colour and a sealed finish.
Small, quick to cast and easy to make in batches for markets.
Solid, weighty bases that feel far more substantial than plaster.
Pour into a planter mould and colour the mix to suit the room.
Terrazzo-effect pieces
For a terrazzo look, cast a few thin slabs in different colours, break them into chips once cured, then scatter the chips into your mould and pour a fresh mix over them. Sand the surface once cured to reveal the chips, then seal.
Tips for Better Casts
Always weigh, never guess
Too much water weakens any gypsum cast. Sticking to 3:1 by weight gives you consistent strength.
Tap out the bubbles
After pouring, gently tap or vibrate the mould to bring air bubbles to the surface before the mix sets.
Mix only what you can pour
With a 30 minute set, mix in batches you can pour straight away rather than one big bucket.
Seal to protect the finish
Sealing with a gloss or matte varnish after 24 hours protects the surface and finishes the piece.
Frequently Asked Questions
Is eco casting powder the same as plaster of Paris?
No. Both are gypsum-based, but eco casting powder is a premium 3200 grade casting powder that's stronger than standard plaster of Paris and fully cures in 2 hours.
What is a good alternative to plaster of Paris for casting?
Eco casting powder is a stronger gypsum-based alternative for moulded pieces such as coasters, trinket dishes, candle holders and planters. It mixes at 3:1 powder to water, sets in 30 minutes and cures in 2 hours.
How long does plaster of Paris take to dry?
Plaster of Paris sets quickly, but thicker pieces can take a day or more to dry right through. Eco casting powder sets in 30 minutes and is fully cured in 2 hours.
Is plaster of Paris waterproof?
No. Plaster of Paris absorbs water if it isn't sealed. Whichever material you cast with, seal finished pieces to protect the surface.
What is the mix ratio for eco casting powder?
3 parts powder to 1 part water by weight. For example, 300g of powder to 100g of water, stirred until the mix is a uniform consistency.
Can I colour eco casting powder?
Yes. Add water-based liquid pigment a drop at a time, building up to around 2–5% by weight of the total mix, and stir until fully dispersed before pouring.
Can I use the same moulds for both?
Yes. Silicone moulds work well for both, and their flexibility makes it easy to release casts without breaking edges.
Plaster of Paris still has its place for practice and kids' crafts. But for coasters, dishes, candle holders and planters you want to keep, gift or sell, a stronger casting powder makes the difference.
Ready to cast something stronger?
SolidCrete Eco Casting Powder in 1kg, 2kg, 5kg, 10kg and 20kg.
