Clay Roller Motorized Clay Roller Accessories. Spraybooths . Waterwash Spray Booth Spray Booth Spares and Accessories Compressor and Spraygun. ... The Gladstone Jar Mills are used to grind ceramic materials in porcelain jars of varying capacity. £1, (£1, Ex VAT) G91 Jar Mill The Gladstone Jar Mills are used to grind ceramic ...