Pottery and the colour Blue

Royal Blue

The History of Blue and White Pottery

Blue is one of the colours of the rainbow and it has become associated with many things over time. Perhaps the connections with the sky and the seas are the most strong. However it also been used to denote cold, loyalty, truth and conservatism. In past eras the blue coloured pigments for clothing were scarce and expensive leading to the colour being related to wealth and royalty eg Royal Blue. It is a colour that is not available as a natural ceramic pigment but needs cobalt ore to be refined to produce the highly intense blue colour. In the early days the ore was roasted and then further melted with a a glass to produce the early pigments of Zaffre and Smalt.

The origins of blue colour in pottery are a little confusing.

Ming Vase

The Egyptians are known to have been making blue coloured pottery since before 400AD but it was the Chinese cobalt blue and white pottery from the the Tang Dynasty onwards that led to a huge interest in blue and white in Western Europe. The introduction of tea to England escalated the interest in pottery tea sets especially blue and white.

Cobalt has been the source of pigments for English blue and white pottery since the eighteen century and these were the pigments used to make the famous Spode patterns of Willow and Indian tree. Since that time blue and white has never disappeared from our lives.

Blue and white in the 21st Century

Now old designs such as Burleigh compete with more contemporary blue patterns in our High St. Denby Imperial blue has stood the test of time being unique in colour, texture and appearance. Similarly, the English style of Burleigh ware created by the unique hand made tissue printing technique continues to attract buyers from around the world. New patterns like Blue Hydrangea from hand made producer Peregrine pottery continue to gain interest from those looking to buy English style with a modern look.

Blue Hydrangea from Peregrine Pottery

Burleigh ware

Denby Imperial Blue

The Pigments

Although modern blue ceramic pigments started with Zaffre and Smalt, their development has continued and modern day pigments provide high intensity with the ability to meet specific colour tones or firing temperatures. Whilst the use of the basic cobalt oxide in glazes is still common for craft or studio glazes looking for a low cost, the use of cobalt silicates and cobalt aluminate pigments has flourished. They extend the inter-mixable nature in glaze or coloured decoration and often provide improved dispersion characteristics. Some examples of the colour tones available using the different pigment types can be seen in the table below.
(NB Web colours are never an exact match for ceramic tones)

Colour name	Colour pigment	Colour shade
Matte Blue	Cobalt aluminate
Mazarine Blue	Cobalt Silicate
Royal Blue	Cobalt zinc silicate
Willow Blue	Special
Azure	Cobalt alumino-silicate
Flow Blue	Na-Ca-Cobalt silicate

Where next for Blue and White?

Whatever your interest blue continues to feature in pottery decoration across the world. I predict this fashion is unlikely to change soon. I would love to hear whether you agree and your thoughts on blue and white and why its appeal continues so strongly?

More information and other technical articles on pottery and ceramics can be found at my website The Potters Friend.

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How to Make Coloured Pottery

The Appeal of Colour

Copper Ruby glaze

The addition of colour to pottery adds so much to its appeal. Whilst white pottery can emphasise the distinctive form of a piece it is often colour which catches the eye! Colour is often associated with a mood or feeling and this varies between cultures and countries. For example red is a very emotive colour and can mean anything from love and romance to danger and fire! Choosing the right colour to make or decorate your pottery however is a matter of personal choice and allows for much creativity and freedom of expression.

Colour can be added to pottery in many ways including body colour, underglaze, inglaze, onglaze and also as a component of the glaze itself.

In this article I will try to review the two main types of ceramic pigment ( raw oxide and ceramic stains) available and how they can be used to produce highly decorative pottery.

In the second of my series on glaze I described how to make a white textured stoneware glaze. 
Simply adding inorganic colouring oxides such as Iron Oxide to such a glaze produces colour but not always the desired colour!  Carry on reading to find out why!

Raw Oxides in Coloured Glaze

Top = Oxides in transparent glaze
Bottom = Oxides in opaque glaze

Copper oxide crackle glaze

It is common for raw oxide pigments to be used used in pottery making. Many studio and craft potters prefer to use cobalt oxide, chrome oxide, Iron oxide and copper oxide as colouring pigments.These oxides give blue, green, yellow-brown, and green-blue respectively on firing in or under the glaze. Often the fired colour of the starting oxide is not the same as the original oxide colour e.g. cobalt oxide changes from black to blue on firing in a glaze. However mixing of these oxides in a glaze, gives variable but often aesthetically pleasing artistic effects on firing. It is for this reason, and the lower cost involved that many studio potters often use these materials.

Iron Oxide and cobalt oxide in glazes

In using oxides as pigments It is important to match the pigment type and content to the glaze to achieve the most consistent results. In the example above iron oxide gives a yellow colour when added to a glaze in small percentage (eg 1%) compared to a brown colour in high percentage (eg 15%). In combination iron oxide and cobalt oxide often give grey or a black glaze colour (see example right). The difference in the colour between an opaque and transparent glaze containing the same pigment content is also marked. In the example above the same pigment content is compared in a transparent glaze (top) and an opaque glaze (bottom). A stoneware textured glaze will produce colour tones similar to those of an opaque glaze.


Organic pigments such as those used in paper printing are clearly not suitable and will simply burn away during firing

Ceramic Stains in Coloured Glazes

Top = Ceramic stains in transparent glaze
Bottom = Ceramic stains in opaque glaze

In contrast to raw oxide pigments, ceramic stains have been specially formulated to create a wide range of colour tones in glaze. In their manufacture they have undergone a heat process and a fine grinding process so that they are highly temperature stable and capable of being mixed together to generate intermediate colour tones. This property is highly valued by large scale manufacturers who need consistency of colour tones. However this all comes at a cost compared to raw oxides.

Onglaze and Inglaze Decoration

Pantone Mugs showing onglaze colours

It is common for high quality whitewares such as bone china and porcelain to be decorated with special colours called onglaze (low temperature) or inglaze (high temperature). These colours use a mix of special fluxes and the ceramic stains identified above to create a wide range of intense, durable colours and bond them to the already fired glaze surface.. Whilst a few studio potters try to make their own, they are best supplied by specialist manufacturers to ensure they meet current legislation and perform satisfactorily in use. These colours are often supplied as powders or pre-dispersed in a liquid allowing them to be applied by hand painting or screen printing. This type of colour is very versatile and is often used to make precision decorative decals for water slide application onto pre-glazed pottery. A new development called Digital printing now allows these decals to be personalised and produced in small quantities making it a cost effective method of decoration for craft and hobby use.

Summary

Clearly there is more to making coloured pottery than is immediately obvious. For those who want consistent colour that can be mixed to give intermediate shades then use ceramic stains either as a glaze component or in decoration products such as inglaze or onglaze colours. For those who want unpredictable but aesthetically pleasing results use oxides as a glaze component or under the glaze. Whichever option you choose using colour creatively will only add to the appeal of your pottery.

Happy Potting
The Potters Friend

More information and other technical articles on pottery and ceramics can be found at my website The Potters Friend.

Go now to sign up for my free newsletter.