Your First Cast: Crushed Stone Tray, Step by Step

Steps

1. 01

   Weigh before you mix

   Divide gypsum and water at 100 : 35 by weight. Eyeballing water is the most common reason a first cast stays soft.

2. 02

   Sift the gypsum in

   Sprinkle gypsum into the water over 30 seconds and let it slake for two minutes — do not stir yet.

3. 03

   Mix to a ribbon

   Stir slowly for 60–90 seconds until the mix falls off the spatula in a ribbon and holds its shape.

4. 04

   Pour and settle the grit

   Pour to two thirds, tap the mould to release air, then scatter the aggregate and top up.

5. 05

   Demould at 20 minutes

   When the surface no longer feels tacky, release the walls evenly and lift straight up.

6. 06

   Sand and seal

   Sand the rim flat, dust it off, then apply two thin coats of sealer 30 minutes apart.