Compiled by Daniel Skeffington
About Surface Therapy
The recent TACA membership survey revealed a significant interest in a regular conversation on glazes, not so surprising given the endless variety available to the contemporary clay worker and the plethora of available information. So we will commence our way through the glaze maze, seeking wisdom from experienced practitioners then bringing it to you here online.
I suggest, however, that the word ‘glaze’ is often casually used to describe a ceramic work’s ‘covering’ – that which is added to a raw (or bisqued) clay piece which covers and/or colours the pot. It follows, though, that not all surface coverings are glazes, so in this series we are going to examine not only glazes but also other surface treatments.
Surface Therapy #1: Who is Billie? Why is she so blue?
Dry Glazes – context, history and characteristics
The term ‘dry glazes’ is wrong! That is if one uses the word ‘glaze’ for its conventional meaning. Frank Hamer, the recognised authority of ceramics vernacular, states:
Glaze: A layer of glass which is fused into place on a pottery body. The glaze provides a hygienic covering on pottery because it is smoother than the body it covers and is non-porous. It is also decorative, providing colour, shine and textural contrast …
So where do dry glazes fit here?
Dry glazes are usually composed of a non-glassy formula, so the most prominent qualifiers from Hamer’s definition – “hygienic covering from a smooth shiny non-porous covering” cannot be satisfied for a typical ‘dry glaze’. However, nobody can deny that dry-glazed vessels can be ‘decorative, colourful or textured’ – satisfying the other Hamer glaze criteria. Perhaps we should start referring to them as non-gloss glazes, or, better still, because the word ‘dry’ refers to both a non-glassy surface and also tactile dryness, we might use the description ‘dry surface coverings’.
The scope of ‘dry surface coverings’ is considerable – from slip with a significant proportion of liquid clay, to engobe (which can be a clay layer with or without additives or colourants), to a mixture without clay elements, or even to a formulation of minerals and oxides. The commonality is that they are responsive to the refractory process. Another feature here is the minimal amount of glass and glass-like materials. Often the terms slip, engobe and dry glaze are used interchangeably.
Margaret Keelan (USA), Feeling the Air, h.37cm, w.7cm, d.7.5cm, coloured slips (engobes).
Gloss glazes, ones that are highly reflective, do not work on pieces that are intricately carved or modelled, as the surface texture is lost and the forms distorted. Dry slips and engobes have been used since antiquity. For each clay civilisation (Egyptians, Persians, Greeks, Romans, Etruscans, Mayans, Chinese etc.), there are many magnificent examples of work. These are profiled in www.ceramicstudies.me.uk, an excellent overview series of web page tutorials by Victor Bryant.
In Australia, slips and engobes have been used as part of the imported Anglo-Saxon pottery tradition since white settlement. Now in the contemporary Australian context, “dry glazes are a common part of the ceramic tool kit”, says Janet DeBoos. “The English potter, Robin Welsh, first sparked interest in satin matt glazes in the late ’60s when he visited Australia, and then Derek Smith popularised them.” [Although not strictly dry, they certainly were not conventionally glassy.] In the early ’70s, teaching institutions, including the then East Sydney TAFE and the Canberra School of Art, encouraged student exploration of dry glazes while in parallel, artists such as Milton Moon, Alan Wallwork, Peter Travis and Brian Newman (UK) were presenting new work with dry surface treatments. In fact, student Billie from the Canberra School of Art first formulated Billie’s Blue  which was to be a hallmark of many potter’s future work including Alan Peascod’s – “Alan is a national treasure and was a brilliant artist who showed us a way of seeing through his use of dry glaze, surface and form”. From then to now, waves of intercontinental cross fertilisation of the knowledge and use of dry glazes has become commonplace. “Their impact (dry glazes) has been enormous for contemporary ceramics – particularly to allow enhanced expression of narrative and sculptural work.”
What we know of dry glazes is they are either under-fired (one or more of their contents are not fired to their full melt because of firing temperature or cooling cycle) or they are over-saturated (the proportion of one or more of the contents is disproportionate to the conventional understanding of how that material responds in a refractory process). For example, the complex interaction between a combination of materials can cause a lower melt than might be for an individual material in isolation. In either or both circumstances the result can be a dry surface. The big contradiction to the above non-glass definitions of dry glazes is that a sub-category of ‘drys’ might include glass (silica) or glass formers, but they are fired to a melt sub-point so that their character is not glass-like, rather they are sintered to appear matt or crust-like – similar to other ‘drys’. Jeremy Jernegan has written the definitive text, Dry Glazes in the Ceramics Handbook Series . Most useful is Jernegan’s classification and description of the various categories of dry surface glazes: Alkalines (high loads of sodium, potassium and lithium), Boron, Lead and Zinc matts, Calcium and Magnesium matts, and Barium and Strontium matts. (Barium matts have been very popular in late 20th century and contemporary work, however their toxicity needs to be considered in the health and safety context.)
CASE STUDY #1
Ruth Fugar  is a graduate from Hornsby TAFE Ceramics where she studied glaze technology under Simone Fraser and Trisha Dean. She uses dry glazes on bisque ware that has had coloured slips applied before the bisque. Contrasting clay body, slip and glaze colours are juxtaposed with each other to highlight the textures of her pots. Ruth attributes the following formula to Simone Fraser.
SF Teaching Dry 
Fired to 1200oC (Cone 6), oxidised atmosphere
Eckalite 2 23 (clay)
Soda Feldspar 16 (high temp glass containing sodium, alumina and silica)
Whiting 28 (flux)
Molochite 23 (grog)
Frit 4193 8 (low temp manufactured glass)
Ruth uses the following colourants:
For Apple Green – Copper Carbonate 6%
For Cobalt Blue – Cobalt Carbonate 2%
For Moss Green – Yellow Iron Oxide 3.5% + Copper Carbonate 3%
Ruth Fugar, 2014, ceramic form using SF Teaching Dry glaze
Ruth Fugar, 2014, test tiles using SF Teaching Dry glaze
Ruth’s application notes
These glazes don’t need to be applied too thickly. In fact I have found if the apple green glaze is too thick it goes black instead of a beautiful green colour. Once the glaze is applied to the piece, let it dry and then wipe back with a damp sponge so the glaze is left in the recesses. All the glazes work well at cone 6. I understand they might also be fired to stoneware temperatures, but I haven’t tried this.
The science behind this glaze
The combination of glaze ingredients in the SF Teaching Dry glaze does not form a glassy coating at this firing temperature as the balance of flux, alumina and silica are not within the limits of a glassy glaze. There are infinite variations possible with this glaze by varying the proportions of any of the ingredients, a good example of the value of testing.
Different dry alternatives
Another well-known and often-used dry surface is one attributed to Mike Kusnik, former technologist of the Western Australia Institute of Technology. This category of glaze is known as a Calcium dry glaze (or Calcium matt).
MK Dry 
Fired to Cone 9–10, reduction atmosphere; best applied by spraying
70% Bone Ash (not synthetic, a high matt agent)
30% Soda Feldspar (contains silica and sodium which are glass-formers and Alumina, a matt agent)
Cream – Iron Oxide 2%
Orange – Iron Oxide 6 % + Titanium Dioxide 8%
Blue – Cobalt Carbonate 2%
Green – Chrome Oxide 4%
Working with a new glaze
The tried and true method of working with a new glaze is first to conduct trials. A systematic approach in discovering the multiple possibilities of any one glaze is well documented in Greg Daly’s Glazes and Glazing Techniques. Greg demonstrates basic and advanced methods of examining a glaze so the artist can make an informed decision of what might be appropriate for the work at hand. His 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, 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 as an attachment to this article. Click HERE to download the sheet.
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 eyewear. For handling instructions including toxicities of individual glaze ingredients, go to www.msds.com
CASE STUDY #2
Alice Rose , who is Australian born, British trained and now a New Zealand resident, became enamored of dry glazes initially because she “loves the matt satin surface of just-dry greenware and wanted to re-create the non-reflective immediacy of that surface without the barrier that glossy glaze seems to create”.
I also found glazing very stressful, and have no head for formulas and accuracy that glaze-making requires. Painting with the Base-Dry with added colour stain onto the surface is fast because it dries immediately; though [it’s] complicated in that I need to remember that the colour in the palette is one shade, [and] after application another, and then will fire to another, usually a darker shade. Some compatibility of stains needs to be observed. Usually a bit of blistering occurs if strong colours are overlaid which cutting back on oxides usually resolves. With a good Base-Dry recipe and the great range of oxides and strong stain colours available now, I am really a painter who works in clay. My dry glazes are easy. They give me a colour palette where I’m delighted with the choices! 
Alice Rose, New Zealand
I have brought the painters still-life two-dimensional interpretation and made it three-dimensional again. This brings with it a degree of distortion and the illusion of depth to the flattened vessel. Sprayed and brushed dry glaze allows me to shade and add depth to my illusions.
JAC online resources – glaze recipes and glaze record template
Surface Therapy #1: Dry Glaze Sheets
Surface Therapy: Glaze Record Template
Greg Daly, Glazes and Glazing Techniques: A Glaze Journey, A & C Black Publishers, 2003, ISBN 0713642769
Linda Bloomfield, Colour in Glazes, A & C Black Pub, 2012, ISBN 9781408131213
Cullen Warner Parmelee, Ceramic Glazes, Cahners Books, 1951, 1973, ISBN 9780843606096
Janet DeBoos, Glazes for Australian Potters, Cassell Australia, 1978, ISBN 0726922129
Thank you to Trisha Dean and Val Gordon for the assistance with technical details in this article.
1,2 Hamer, Frank, The Potters Dictionary of Materials and Techniques, Pitman Pub, 1975, (US), ISBN 0823042103
3 Billie’s Blue recipe, see downloads to this article
4 Simone Fraser in conversation with Daniel Skeffington; see also Alan Peascod – Artist of Exceptional Talent, Mansfield Press, 2010, ISBN 9780646524733
5 Notes in conversation with Janet DeBoos, August 2015
6 Jeremy Jernegan, Dry Glazes, Ceramics Handbook Series, Uni of Penn Press, 2009, ISBN 9780812220971
7 Ruth Fugar, https://instagram.com/potterybyruthfugar/
8 SF Teaching Dry recipe, see downloads to this article
9 MK Dry recipe, see downloads to this article
10 Greg Daly, Glazes and Glazing Techniques: A Glaze Journey, A & C Black Publishers 1995, ISBN 9780713642766
11 Alice Rose, www.alicerose.co.nz
12 Alice Rose in conversation with Daniel Skeffington, August 2015