Glaze Questions - Potclays Ltd.

How should I safely handle powdered ceramic materials?

Dust from powdered ceramic raw materials, glazes, slips and clay can cause health problems if not properly controlled. The Health and Saf… Read More About This Question

Why is my bright gold lustre dull?

This is most obvious with the bright gold but can happen with any lustre. The surface is matt and sometimes discoloured.The problem is one of … Read More About This Question

Which of your glazes are vegan-friendly?

This is a question we are asked increasingly often. We have approached our glaze suppliers and detailed their responses below. As far as Potcl… Read More About This Question

Why hasn't my special-effect/reactive glaze fired as expected?

Artistic/special effect glazes usually require a generous application to achieve the desired effect. Varying the heatwork will produce differe… Read More About This Question

What should the specific gravity be for my dipping glaze?

Very generally speaking, ideal specific gravity for most dipping glazes is between 1.4 and 1.6. However there are a lot of variables which&nbs… Read More About This Question

Why does my tin white glaze have a pink tinge?

This fault is caused by volatilisation during the firing and may produce a variety of other undesirable effects.In the case of the example, th… Read More About This Question

What’s causing the rough, pitted surface on my decal transfer/on-glaze enamel/lustre decoration?

The glaze surface appears to have a layer of sugar stuck to it. In actual fact it is a mass of tiny bubbles. In industry this fault is known a… Read More About This Question

What’s causing my glaze to blister?

Blisters in the surface of the glaze are the remnants of bubbles which have burst but not completely healed during the firing. The reason for … Read More About This Question

What’s causing my fired glaze to be full of bubbles?

Bubbling in glazes can occur for a variety of reasons. It may be the result of some impurity (contamination) in the glaze burning away. For ex… Read More About This Question

What's the recommended firing process for clay and glazes?

We generally recommend biscuit firing at 1000-1060C then following with a glaze firing to a higher temperature which matures both the clay and… Read More About This Question

What is the optimum firing rate to use?

The optimum rate depends upon the thickness of the pots and clay type e.g. thin cast and grogged bodies can be fired quicker than thrown and u… Read More About This Question

How can I resolve crazing?

Crazing takes the form of fine cracks spread throughout the glaze. Craze lines may be so fine that they're difficult to detect with the naked … Read More About This Question

At what temperature should I fire my glaze?

The glaze firing range is that range over which we expect the glaze to produce the desired effect without running, pinholing or bubbling. User… Read More About This Question

Why has my transparent glaze fired ‘milky/cloudy’?

Glossy Transparents: This is caused by devitrification which is the formation of crystals, particularly of calcium borate, which sometimes oc… Read More About This Question

Why has my glaze peeled?

Peeling or "shivering" is the opposite of crazing and so is typically caused by overfiring of the clay. Unfortunately this fault cannot be rev… Read More About This Question

When should I clean out my sedimentation tank?

Sedimentation tanks should be cleaned out regularly to prevent the sediment level building up (and also preventing odour). The higher the leve… Read More About This Question

What’s causing the purple discolouration in my fired lustre?

Lustres are a very thin (molecular) layer of metallic components deposited in the surface of the glaze. Quite often, the inexperienced user ca… Read More About This Question

What’s causing my glaze to pinhole?

Pinholing in glazes can be caused by a variety of reasons. Firstly it can be caused by volatile materials burning away from within the clay pa… Read More About This Question

What are Once-Fire glazes and how do I use them?

‘Once-fire’ is the term given to glazes applied to unfired clay rather than bisque ware. This may seem to be the ideal way to work… Read More About This Question

How should I apply a glaze made up from a powder?

Powdered glazes, once mixed with water according to the recommended guidance, are suitable for dipping, pouring or spraying onto the piece. Th… Read More About This Question

How much brush-on glaze do I need to cover a specific area?

As a general guide, allowing for 2-3 coats application of commercially-prepared brush on glaze, you will need approximately 2 litres of brush-… Read More About This Question

How do I stop my glaze from settling out ("hard-panning")?

Fritted glazes are particularly prone to hard-panning. Bentonite clay (sku3411) is a suspending agent which slows down the settling-out of gl… Read More About This Question

How can I change my shiny glaze into a matt one?

All glazes are inherently shiny, even when they appear to be matt. A shiny glaze reflects the light straight back to the viewer (just like a m… Read More About This Question

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