Sodium silicate (Na2SiO3) or water glass is a common deflocculating agent for casting slips and is almost always used together with soda ash. This combination is effective and cheap, but wears hard on the molds and the risk of overdosing is high if the adjustment amounts are small.

Today, there are alternative and more modern deflocculation agents that are more gently on the moulds, see e.g. Dispex [2864 alt. 2865].