Slip Casting Questions - Potclays Ltd

Can I use hand-built add-ons on my slip cast piece?

Even when casting slip is made from the same clay as the hand built pieces, the manner in which the clay particles align themselves is differe… Read More About This Question

I have cast a large plate mould, but when opened, some areas have not formed a cast. What’s gone wrong?

This is a common problem with ‘closed back’ plate moulds, and is caused by the slip being too thick to reach all areas of the moul… Read More About This Question

What recipe should I use for making a casting slip from a powdered clay?

Casting slip recipes vary depending on the clay, we recommend the following as a good starting point but be prepared to adjust to ensure the c… Read More About This Question

Why is my cast very soft (flabby) and distorts when handled?

This problem is caused by either an under-addition of deflocculent, or by an excess of sodium carbonate. Add more sodium silicate to rest… Read More About This Question

Why is my casting slip so slow and difficult to drain from the mould?

When the cast thickness has built up to the desired amount, it must be possible for the excess slip to be emptied from the mould without needi… Read More About This Question

Why is my casting slip thick and gloopy?

Casting slips are thixotrophic so upon standing they can thicken. This is usually easily rectified with a thorough stirring, but if … Read More About This Question

What's causing the horizontal lines around my slipcast ware?

This is a fault known as ‘wreathing’ and is caused by the slip casting or skinning over before the mould has been filled, leaving … Read More About This Question

What’s causing the discoloured patch and thin-glazed area on the cast?

This problem is known as ‘casting spot’. It is caused by the slip constituents separating at the first point of contact of the sli… Read More About This Question

Which deflocculant should I use when making my own casting slip?

Sodium Silicate Na2SiO2 is the most popular deflocculant used in casting slips and has been so for many years. It's nearly always used with so… Read More About This Question

Why are my casts brittle, difficult to fettle and difficult to handle?

If your cast is very dense but low in strength due to the cast forming too quickly, this is brought about by either an over addition of defloc… Read More About This Question

Why are my pieces taking so long to cast?

If you notice that the slip takes a much longer time to build up to the normal thickness, or appears to stop building any further ca… Read More About This Question

Why do my slipcast items have small pinholes on the outer surface?

This is caused by air bubbles becoming trapped between the slip and the mould surface. This may be due to an excessively worn mould surface (i… Read More About This Question

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