Playing with porcelain has finally inspired me to examine the rich and rare phenomenon of Copper Reds. The glaze has a fascinating history through the last 1000 years of Chinese ceramics: through its visual association with blood, and as a colour that was the preserve of the Ming emperors. It has been prized for its vivid colour; it is also notoriously difficult to achieve, due to the fugitive nature of the copper responsible for the colour.
'Hong' is the Chinese word for red, and the colour has been central to Imperial rule since the advent of the Ming Emperor. The best Ming red was perfected in the reign of Xuande, and is known as jihong, or sacrificial red. The use of the character ji meaning sacrificial has been described by Bushell as "the colour of the sacrificial cups which were employed by the Emperor in the worship of the Sun". Another, more common term is 'xianhong' or fresh red: this was used in Ming times and more widely copied in the Qing Dynasty, and draws reference from the bright red colour of fresh blood spilled from the cut throat of an animal. There are many others, usually with a descriptive term relating to blood, such as ox-blood (sang-de-boeuf), calves blood, or others such as pigs liver, for those more muddy reds that failed to excite!
First firing of tests was encouraging, with good red developing but generally too 'livery' in tone, a rather murky purple red (called pigs liver, for good reason!)
Subsequent firings have shown more illumination on the fine tuning needed to give a proper blood red, with a spectacular little porcelain bottle emerging ...
Small modifications to the recipe and an altered firing schedule then produced some outstanding reds... a very deep, blood red with white rims but still a stiff glaze (that is, not so fluid that it runs off the pots).
In common with the historical precedent, I have been keen to use a small quantity of ash in the red glaze, as it brings a selection of some of the minerals which are an integral part of the fluidity and colour: calcium, iron, phosphorous and silica…the tiny amount of copper which is key to the colour is the only mineral I have to add as a processed material, copper oxide. The problem with using ash is its variability…each batch is different, depending on what timber I burned in my fireplace to give me the ashes. At some points over the years since I started making copper reds, the quality of the glaze has ‘gone off’ a little, as the ash changes. My current batch of ‘Falls Ash 12’ seems to work well, and I have learnt to reserve a sufficiently large batch for the red glaze only, so that it will last some years. My standard Ash glazes use a softwood blend of pine and willow for a glassy green glaze, and cherry / plum for a more buttery semi-matt pale glaze.