SURFACE THERAPY #2: COPPER REDS

Compiled by Daniel Skeffington

ABOUT SURFACE THERAPY

Copper reds are the topic for the second in the series featuring historical perspectives, Australian contemporary use, basic theory and science, further reading references, and a working recipe for you to try. Surface Therapy has compiled in response to requests from the JAC readership and is intended to be a ‘starting point’ through the glaze information maze. Featured artists include Barbara Mason (NSW), Brian Keyte (VIC) and Ian Beniston (WA).

COPPER RED (SANG DE BOEUF) – CONTEXT, HISTORY AND CHARACTERISTICS

When copper is reduced in the kiln it turns red. This incredible phenomenon is even more startling when you consider that in an oxygenated kiln (pending alkaline or acidic partners), copper delivers magnificent blues and greens. This alchemy has been the key reason why copper reds have a long pedigree in the ceramics record.

Copper has been employed for its red response in several different glaze settings, including as a glass, as an underglaze illustration media, and also in various lustre glaze processes. They were used some 3000 years ago in areas in the Middle East (today’s Iraq) in both glass and ceramic ware, and copper reds were significantly developed and championed in Jingdezhen (China), and also in northern China, starting in the 14th century and continuing into the 16th century. Both regions seem to have discovered, lost the knowledge and then re-discovered their copper red story independently of each other.

Some accident is said to have happened to make a kiln-load of pots containing a copper element be fired in a ‘reduced’ kiln. Out came red-glazed pots and then obviously the phenomena was empirically sought, discovered and replicated. From China the mythology of the fraught potter desperately trying to emulate his first red pot to appease his threatening Emperor is well known. Apparently he couldn’t get the result twice. In sheer grief he jumped into the next firing (therefore adding fuel to burn up the oxygen, in so doing making a reduced atmosphere), and his attendants, sad but continuing the work, revealed a kiln full of red when the firing was complete (perhaps some bone ash was found as well!).

It is not suggested by your author or your case study contributors that you resort to such conclusive measures; however, the frustrations of working with copper to get a desired great red outcome are well-voiced in the following text.

In Australia, as internationally, there are pockets of copper red enthusiasts whose toil and torture are to deliver their win over the many copper red challenges. Barbara Mason of Sydney says copper reds are “the potters pot, like Tosca is for sopranos”. All three of our contributors insist that it’s not necessarily only about copper in the copper red story, rather many elements need to be absolutely right to achieve a result – and this combination of elements and circumstances, if lined up correctly, is blissfully rewarding. So much so that Ian Beniston [1] of WA claims that he can command a much higher premium price for his copper reds than he can for an equivalent celadon. It transpires that copper reds are sought after and admired by the buying public – and with Ian’s work it’s not hard to see why. So it’s not only for the challenges discussed here, nor the magic of creating a brilliant ripe, rich, red-fruit coloured vessel, nor even simply the challenge of achieving the ‘sweet spot’ – there’s money to be made as well!

Above: Ian Beniston, 2008, Copper Red with Bamboo, h.38cm

ANOTHER STORY …

Not all copper reds are full blooded! Some call them ‘Flambé’. Copper also has a place to play in the elusive Peach Bloom glaze [2] (jiang dou hong), low-fired copper reds, and reduced paste lustre. Not much seems to be documented about Peach Bloom despite its attractive and subtle pastel-like qualities, however there is a good web-based resource on Ceramic Arts Daily [3], which details some research, trialing and recipes. We shall leave lustre for a future Surface Therapy instalment.


Above: Peach-bloom Glazed Beehive Waterpot with Kang Xi Mark


Above: Peach-bloom Glazed Waterpot with mark and period of Kang Xi


Peach-bloom glaze

SO WHAT'S HAPPENING SCIENTIFICALLY IN A COPPER RED? 

Copper exists in one of three states – cupric oxide, cuprous oxide or metallic copper. When a copper-containing glaze is heated, the copper carbonate will be decomposed by 500ºC giving off carbon dioxide and leaving copper oxide in situ. The copper is starved of oxygen as the temperature rises and the atmosphere is reduced, so it develops into a state midway between ‘dissolved in solution’ and ‘solid in suspension’ – it becomes ‘colloidal’. Above 1083ºC copper becomes molten and mobile and moves within its holding solution. There is a measure of disassociation of the copper into minute ‘aggregates’ of copper. Then, still in the continuing oxygen-deprived environment, as the temperature decreases the copper atoms come out of solution, ‘solidify’ and clump together to form crystals. The red colour we see is produced by the absorption of light by these now ‘reorganised metallic copper crystals’. The degree of red is associated with how many crystals are clumped together, so the greater the concentration, the more red and vice-a-versa. This explains the nature of white rims occurring on breaks on copper red vessels. The glaze is thinner there, therefore there are fewer crystals available to sparkle! (Also note there can be too much of a good thing so that beyond a certain size of crystallite formation a ‘muddy’ or liver-like ‘livery’ colour will result – not pretty! The Chinese named this ‘Mule’s Liver’.)

Much has been written about the science of copper reds in considerably more detail than above. For a more extensive account see Currie [4], Wood [5] and Bailey [6] or search online where ‘Digital Fire Reference Database’: Karl P. Platt [7] is recommended.

“There is more to a copper red than meets the eye”. Ian Beniston [8] is a self-taught, full-time working potter in the Margaret River region of Western Australia. Ian’s copper red pots are typically rich and lush red. “I want to make people respond to my pots. The drama and emotive nature of copper reds wins this reaction. There’s something about them – even for those who spruke ‘I don’t know much about art, but I know what I like’ – they’re a winner!” [9] The response of colour, the depth and richness of colour, the sometimes variations of colour is what makes the journey of creating copper reds, this ‘most difficult of glazes’, worth it. Consideration should be given to form. Copper reds work best on ovoid shapes where there is less texture. “A good copper red is a powerful colour so if there is too much going on with the shape and/or surface texture, the reading of the finished work is confused. A smooth surface provides clarity for this glaze”. [10]

Above: Ian Beniston, 2005; Large Bowl with Copper Red and Iridescent Blue; h.10cm, diam.48cm

CASE STUDY #1

Barbara Mason is a Sydney-based potter who exhibits work in two Sydney locations{11}. Barbara is represented in the Manly Regional Art Gallery & Museum, Sydney’s Powerhouse Museum, and Launceston Gallery’s collections. She was an exhibiting member of the Potters Society of Australia. She’s been potting for more than 45 years, starting when she needed a creative outlet from a demanding family life then teaching part-time ceramics at Gymea TAFE for 15 years and selling her work as an important part of her family’s income. She is now financing an opera addiction!

Of copper reds, Barbara says, “I was drawn to the challenge to get it right. They are so spectacular. Of all the glazes available to me, copper reds are the ones that require the most respect and diligence. It took me three years to produce a result I was happy with.”

Barbara Mason Copper Red [12]

Fired to 1220ºC (Cone 9 touching*)
Reduction atmosphere from 865ºC to 1050ºC

Nepheline syenite          38% (clay)
Gerstley borate              17% (glaze flow)
Whiting                           15% (flux)
Silica 400                        30% (glass former)
Copper carbonate           0.4% (colour)
Yellow Iron oxide             0.3% (colour)
Bentonite                        1% (suspension medium)
Tin                                  1% (stabilises copper, potentiates colour)
*touching – the cone curves over and the tip just touches the base of its placement

Firing schedule:
Overnight low flame to 200ºC to 300ºC
100ºC per hour up to 865ºC
Heavy reduction (using burners and damper) to 1050ºC over 2 hours
Mild reduction for approx. 6 hours up to 1220ºC (Cone 9 touching)
Close kiln

Barbara’s best tip: “Better to go too slow than too fast!”

See also Bailey, Oriental Glazes [13] for 11 different CR recipes.

Above: Barbara Mason, 2008, h.20cm, w.20cm

WORKING WITH A NEW GLAZE

The tried and true method of working with a new glaze is to first conduct trials. A systematic approach to discovering the multiple possibilities of any one glaze is well documented in Greg Daly’s international bestseller Glazes and Glazing Techniques. [14] Greg demonstrates basic and advanced methods of examining a glaze so the artist can make an informed decision about what might be appropriate for the work at hand. Key points are “document, document and document” and be methodical.

Once you have found a glaze to your liking and there is a pleasing aesthetic fit to your work (not all glazes ‘fit’ all styles of work), be sure to record the particulars of your glaze, your fired result, and thoughts for further investigation. One such record keeping document can be accessed, downloaded and printed from the Australian Ceramics website, australianceramics.com/journal/glazerecordtemplate

Note: Always apply appropriate Health and Safety practices and protection when working with glazes and ceramics equipment. Always use a P2 dust mask, rubber gloves and protective eye ware. For handling instructions including toxicities of individual glaze ingredients, go to www.msds.com.
 

MASTERCLASS: A PRACTITIONER'S LENS

For Brian Keyte [15] (VIC), it’s simply (read ‘importantly’), a matter of “getting all the ducks in a row”. Copper reds for Brian have been a twenty-year pursuit. His background is in mechanical engineering but when he came across Greg Daly’s glaze book he saw the potential for some research and development and was hooked. Brian’s focus is on ceramic forms and their relationships with glaze – the aesthetic fit to the physical form. So 20 years into his copper red journey – and with continuing representation in Beaver Gallery (ACT), Skepsi Gallery (VIC), Framed (NT), and Stony Creek Gallery (VIC) – he is well-placed to impart some wise saws for the copper red ‘newby’.

Above: Brian Keyte, Venturi Bowl, h.10cm, diam.60cm

Brian’s main message of hope is that your toil will eventually pay off – without having to jump into the kiln. To embark on the copper red journey is to accept that there will be failures. From his first output he suffered up to a 40% failure rate. Now, after years of patient work, he is happy to report a 90% success rate. Indeed, a quote Brian remembers of Edison’s retort when asked if he was disappointed at the lack of success of his many hundreds of trials in the transmission of electricity, Edison replied, “Results! Why, man I have gotten a lot of results! I now know several thousand things that wont work.” [16] It doesn’t take a rocket scientist to teach us the value of experimentation – it takes an electrician!

Brian has come to love copper reds for the variants and interplays of colour. They are so evocative, like an aged cab sav or deep, red, ripe cherries. As a student of copper reds Brian has found that experience has been his best teacher. Here are his tips:

• Be mindful that no two batches of the glaze will be the same. The ingredients, although the same material, may come from a different source and this makes a difference.
• It is essential to test, test, test.
• Test on testing bowls, not tiles, to correctly predict the glaze behaviour on your intended work.
• Spraying on the glaze is the only method that gives true justice to the glaze. Expect a high failure rate if dipping or brushing.
• The clay body should be white; other colours may muddy the red colour response of the glaze.
• In general, the glaze should be applied reasonably thickly (as above).
• The spraying protocol should be thicker at the top rim and thinner at the base to allow for the in-firing movement of the glaze. This will give an overall evenness of glaze thickness as a fired result.
• Firing schedule recommendation: Early light reduction, back off to Cone 9 and end the firing with no reduction.
• I choose not to use Gerstley Borate (low temperature flux) in my glazes; kiln shelves are too expensive to replace!
• Copper red glazes need Tin as a stabiliser. Use in proportion Tin:Copper / 2:1.
• Make sure you are meticulous in your approach. Be the best you can be at making, firing, glazing – all things. Copper reds take no prisoners.
• Most importantly, know your kiln, know your burners, and know how to reduce effectively. Learn how to read your trials and to diagnose and treat problems that you see. •   Find a mentor – someone who has had some experience. It might reduce your sleepless nights.

Above: Brian Keyte, Fibonacci’s Rose, triptych of stacking, wave rim spheroid bowls, largest, diam.16cm

JAC ONLINE RESOURCES – GLAZE RECIPES AND GLAZE RECORD TEMPLATE
Surface Therapy #2: Glaze Record Sheets Barbara Mason
Surface Therapy: Glaze Record Template
ceramicartsdaily.org 

ceramicrecipes.org
pinterest.com/delicion/glaze-recipes

BIBLIOGRAPHY
Stoneware Glazes. A Systematic Approach, Ian Currie, Bootstrap Press, 1985, ISBN 0958927529
Chinese Glazes; Their Origins, Chemistry and Recreation, Nigel Wood, A&C Black, Reprinted 2007, ISBN 9780812234763
Oriental Glazes, Ceramics Handbooks, Michael Bailey, A&C Black, 2004, ISBN 071366214X
Glazes and Glazing Techniques: A Glaze Journey, Greg Daly, A & C Black Publishers 1995, ISBN 9780713642766
Glazes for Australian Potters, Janet DeBoos, Cassell Australia 1978, ISBN 0726922129
The Complete Guide to High-Fire Glazes, John Britt, Lark Books, 2007, ISBN 1579904254
Techno File: Four Ways to Reliable Red Ceramic Glazes; Ceramics Daily; J. Harnetty June 13, 2011; http://ceramicartsdaily.org/ceramic-glaze-recipes/glaze-chemistry-ceramic-glaze-recipes-2/techno-file-four-ways-to-red/

Thank you Val Gordon for the assistance you gave with technical details in this article.

1 Ian Beniston, senseipots.com.au
2 see Glaze Sheets for recipes
3 ceramicartsdaily.org/ceramic-supplies/ceramic-glaze/experiments-in-peach-bloom-extensive-testing-reveals-secrets-of-an-elusive-ceramic-glaze/
4 Ian Currie, Stoneware Glazes, A Systematic Approach
5 Chinese Glazes, Their Origins, Chemistry and Recreation, Nigel Wood
6 Oriental Glazes (Ceramics Handbooks), Michael Bailey
7 digitalfire.com/4sight/education/copper_red_glazes_115.html
8 Ian Beniston, senseipots.com.au
9,10 Ian Beniston in conversation 2015
11 Barbara Mason exhibits at Kerrie Lowe Gallery, Newtown, and she is a long-time member of the Inner City Clayworkers Gallery in Glebe, NSW.
12 Barbara Mason Copper Red Recipe Sheet is downloadable and printable from HERE.
13 Oriental Glazes (Ceramics Handbooks), Michael Bailey
14 Glazes and Glazing Techniques, A Glaze Journey, Greg Daly
15 Brian Keyte – salt-art.com.au; www.skepsionswanston.com.au
16 Edison: quoteinvestigator.com