Colouring oxides are added to glazes to produce colour. They dissolve in the glaze to produce transparent glazes with more depth than those made using commercial stains. I prefer to add only small amounts of colouring oxides to give pale, watery transparent glazes.
The glaze recipes are in my book The Handbook of Glaze Recipes. The book shows how to make a wide range of subtly coloured glazes predominantly using the colouring oxide rather than commercial stains.
My next book Science for Potters is coming out later this year.
I have been asked to teach several glaze courses in 2017.
A new pottery school is opening in Forest Row in Sussex. I will be teaching glazes there 0n 17-19 February 2017. Contact Katrina Pechal on 0789 444 7938. You can visit the school when they open in December, courses start in January with tutors including Stephen Parry and Ruthanne Tudball.
The founder Katrina Pechal says, “ I am saddened to see so many high-level ceramics courses around the country closing. My days training at Camberwell School of Art were inspiring, having lessons with famous potters like Takashi Yasadu, Colin Pearson and Ewen Henderson among others was a great privilege and I want the next generation of potters to have the same opportunities. I have noticed a recent increase in the popularity of pottery, thanks in part to the BBC’s “The Great Pottery Throw Down. I feel this is a perfect time to move to a bigger site with better facilities where I can help students to train and develop their craft”.
Forest Row School of Ceramics will be based in the Rachel Carson building at Emerson College, set in beautiful grounds within walking distance of the village. It offers outdoor space, which Katrina needs for a kiln site (a kiln-building workshop run by Joe Finch, Potter and author of Kiln Construction (a brick by brick approach), is already planned for early next year). Emerson also has more classrooms Katrina can utilise as she expands plus affordable student accommodation it needed.
Forest Row is three miles from East Grinstead in Sussex, situated next to the idyllic Ashdown Forest yet within easy access of the M23/M25 and a short drive from Gatwick Airport, the South Downs and the creative hub of Brighton.
I will also be teaching colour in glazes at West Dean College on 5-9 March (the course is now full but you can try the waiting list), and demonstrating throwing and glazes all weekend at the Scottish Potters’ Spring Workshop at Tulliallan on 10-12 March.
For anyone in London there are glaze courses at the Morley College in February and April but I will not be teaching them.
Exciting news: I will be teaching a glaze course in Belgium in 2018.
If you can’t come on a course, you can still learn from my books.
My latest article, in Ceramics Monthly September 2016, explains the science behind colour.
I am really interested in why things are coloured. When white light falls on certain objects, they absorb some colours of light and what we see are the remaining colours of light reflected from the object. Some objects, like trees and grass, use light as energy in photosynthesis and absorb red and blue light, causing them to appear green (the three primary colours which make up white light are red, blue and green). Other objects such as coloured gemstones and glazes have transition metal atoms in them, either as impurities or added intentionally. These absorb some colours of light by promoting some of their electrons to higher-energy orbitals. For example, cobalt silicate in glazes absorbs yellow light. The colour we see is the complementary colour, blue. The colour depends on the type of transition metal and the shape of the electron cloud around it, which can be different in a gemstone from in a glaze, for example, chromium impurities give a red colour in rubies but usually give a green colour in glazes. This is because the surrounding atoms in the ruby crystal are forced closer to the chromium atom than in a glaze.
Recently I have noticed a beautiful pink-grey-mustard colour combination in art, prints, textiles and interior design.
I have made a collection of porcelain bottles with the same colour combination. The bottle shapes are inspired by the still life paintings of Giorgio Morandi. The glazes are all made from raw materials in my studio. The mustard yellow comes from nickel and titanium, while the pink is made from rutile and tin oxide. These are chalky matt glazes with microscopic crystals covering the entire surface of the glaze. The pale grey is made from a combination of cobalt and nickel oxides in a dolomite glaze. Where the glazes overlap, there are interesting reactions. The dark grey box frame was made by Henry Bloomfield.
I will be showing the new bottles and vases in the British Craft Pavilion at the London Design Fair, the new name for Tent London at the Old Truman Brewery on September 22-25. Also during the London Design Festival, on 20 September I will be demonstrating throwing on the wheel at the Canvas Home showroom.