The wonderful world of glazing

When it goes well it’s wonderful, when it goes wrong it’s anything but…
In past newsletters I’ve touched on some pottery basics – clay, turning, firing, and even glazing. But my glazing skills have really been put to the test in recent weeks as I grapple with trying to work out new methods for my current project. What might seem straightforward in the world of colour is extremely complex in the world of glazing.
The glaze is the final layer, the coating that fuses with a ceramic item in firing, intended to colour, decorate, strengthen and waterproof that item. As a rule, glazes can be classified into two types: those that are fired at low temperatures – up to 110° centigrade – seal and waterproof the clay, and are also decorative; and those that I use, fired at high temperatures – at least 120° – which are absolutely impermeable, amalgamating with the surface of the clay to improve the quality of the finished article. They also have a strong aesthetic element. I prepare my own glazes, and they are what give my pottery its unique character.
Raw glazes are compounds of silica, minerals, and metal oxides, and are applied in various ways, mainly by dipping the item into a glaze solution or by applying it directly, either with a brush or by spraying.
That might sound straightforward, but a lot can go wrong:
If the firing temperature is too low, glazing will not be uniform, and if it doesn’t fit properly, it’s like a badly made item of clothing – too big or too small. If the firing temperature is too high, the glaze will run.
If poorly applied, the glaze will blister, be uneven, and can also fail to adhere.
Incorrectly mixed raw materials can cause crystallisation or air pockets in the main body of the clay;
and lastly, there are kiln accidents – items stick together, power cuts create havoc, and small pieces of debris cause imperfections.
Essentially, patience and determination are what you need. Good work is often lost when experimenting, but when you finally get it right – it makes up for everything.

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