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The shiny surface of our pots – the glaze – makes use of wood ash from local trees.

Wood ash, mixed with other ingredients, will melt at high temperatures and form glass. The glaze on a pot is really just a thin layer of coloured glass. The Ancient Chinese were the first people to use wood ash in this way.

Each type of tree makes a very different glaze.

Pot 17 in the Main Gallery shows Beech tree glaze. This pot has two glazes on it. The first glaze applied to the pot was a glaze rich in iron, called Tenmoku.  Beech ash glaze was then applied on top of the Tenmoku glaze. The two glazes react with each other in the fire. Beech ash glaze consistently gives this greeny-blue colour when used in this way. If you come to Abersoch you can see the beech trees that were used for this glaze. They are on the main road between the Gallery and  Abersoch, opposite Llanbedrog Riding Stables. The wood came from pruned branches that had been overhanging the road.

The brown and yellow vases (Pots 33 and 34 in Main Gallery) have an Ash tree glaze. The Ash trees came from Machroes Farm, near Bwlchtocyn. The Ash trees had died some years prior to burning.

The white colour in pots 18, 22, and 28 is Gorse ash. Gorse is one of the few readily available woods in this part of the world. Farmers often grub out gorse from their land and are usually delighted for you to take it away. It’s a prickly process of course, but well worth the pain. Gorse ash makes a similar glaze to a famous, old Japanese ash glaze called Nuka, much favoured by the Japanese master potter Shoji Hamada. Nuka glaze uses the ash from burnt rice husks. This ash is almost pure silica – one of the essential ingredients in glass, or glaze. Gorse grows almost anywhere and can stand up to the fiercest winds. Silica is strengthening to plants, so Gorse, like rice husk, may have a high silica content. This is just a theory, for which we have no evidence. If anyone knows of a gorse ash analysis, we’d very much like to hear from them.

This leads on to the fascinating question of why different trees make different glazes?

Different trees draw up different minerals from the soil. Iron, phosphate, calcium, silica and many other elements are drawn into the tree throughout its life, surviving in the ash when it is burnt. These differences are reflected in the characteristics of each glaze. Used without an under-glaze, the differences between the glazes from different trees is significant, but not great. At Abersoch Pottery we use a Tenmoku under-glaze to highlight the differences in the ash glazes.

If you compare the white Gorse Ash of Pot 22 with the blue of Mysterious Blue Ash in Pot 3, the difference is striking. Both these pots have been glazed in exactly the same way. (same amount of Tenmoku glaze, same amount of ash glaze, achieved by dipping the pots for exactly the same amount of time in glazes made in identical ways, with equal, measured viscosities).

Mysterious Blue is such an unusual colour that we can’t quite bring ourselves to reveal the tree it comes from. We believe in sharing knowledge and happily do share 99.9% of it, but don’t feel ready let go of this secret – although we probably will in time. We console ourselves with the thought that most potters confess to harbouring one or two secrets!

Many with expert knowledge will suspect that some cobalt has been added to Mysterious Blue. Cobalt is widely used in pottery to make blue, as in the famous Chinese blue and white porcelain. But no cobalt has been added to Mysterious Blue – the blue colour comes from whatever is in the tree.

The preparation of ash glazes is a time consuming process. To bring a tree’s characteristics to the fore, great care must be taken to obtain a pure sample. It’s important that no logs of a different tree type are accidentally put in the log burner, and that no soil  contaminates the logs. We avoid paper when fire lighting. With gorse, it is possible to use nothing but gorse – gorse twigs with dry needles make fantastic firelighters.

The wood ash from the fire has to be washed and sieved through a fine mesh, and then dried before it can be mixed with other ingredients like silica and potash feldspar to make a glaze. Ash is a bit of an escapologist - small particles try to escape to the air or down the sink during the process of preparation. It is vital to stop this from happening – the smallest ash particles are vital to the glaze. Gorse is the greatest escaper: the faintest movement of air will lift clouds of precious ash from the dry powder. And when it is being washed, it takes longer than any other ash we use to settle – the water in the bucket can stay slightly cloudy with fine gorse particles for ten days or more. If the water is poured away before it is crystal clear, some of your best ash is going down the sink. You know you’ve got it right when the ash in the bottom of the bucket has a wafer thin layer on it that glows like silver. These are the very finest gorse particles. This silver glow is unique to gorse in our experience - we don’t see anything like this effect with any of the other ash glazes we use.

Wood-fired stoneware will last for a thousand years or more without changing – unless, of course, the pot is dropped. A pot with an ash glaze made from a particular tree from a particular place fixes something of that tree, and that place, forever. Whenever we see a pot with an Ash tree glaze made from the dead Ash trees of Marchroes Farm, we think of Bob Griffiths, the farmer who loved and tended the trees for fifty years before he passed away. The Ash tree pots seem like an enduring testimony to Bob, capturing a whisper of his life on clay.

In a way, any pot with an ash glaze is an enduring testimony to the tree from which it was made, to the people who helped and loved that tree, and to the earth from which it came.