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Wads                                                                               by Owen Rye

First published in The Logbook, Issue 2, May 2000, pages 3 to 7.

Sounds like an acronym for some obscure government department: WADS. I am slightly worried that in writing about wadding, I might be getting mired in the trivial. I am reminded of a Northern English character in a television sketch by Mjchael Palin, endlessly comparing shovels and the slender distinctions between them, with his audience falling asleep standing up.

Nevertheless, I will persist on the basis that the ultimate quality of work coming from a wood-fired (or indeed any other) kiln is derived from subtleties explored and perfected in every aspect of the process. I have spent much time working to get all aspects of my process working together so that there is a harmony in their consequences. This includes seeming trivial considerations such as wadding.

In my first ventures into anagama firing some 20 years ago, I simply stacked the pots in contact with each other in the kiln. The consequences were not as bad as you might expect. Some of them did stick together slightly but generally they separated with nothing more than a minor scar, which contributed to the character one critic called ‘rustic’. This technique is one I would still use in firings where the temperatures are held low deliberately in order to achieve dry glaze qualities.
Looking back at some of these earlier works reminds me that keeping anagama temperatures below about 1160 — 1180C (2120—2156F) throughout firing gives some very beautiful dry ash qualities, subtle colours and very delicate contact colours — soft pinks and oranges. High iron clays under the right circumstances give very strong red colours (see for example wadmarks on some Bizen ware by Fujiwara Kei).

Firing higher produces more melting of ash, hence more variety of surface corresponding to microclimate variations in temperature and atmosphere. Surfaces become more complex and forms become more distorted depending on stacking methods. The extra melting of surface ash deposit can fuse pots together, or to shelves or the kiln itself. To get them apart without destruction we use wads. At their most basic wads exist for separation. The basic thinking is that if wads are very refractory then they will not fuse to anything, and further, if they have a high alumina content they will not become glazed by ash themselves. Hence the old idea of wads being made from half fireclay, half alumina. In terms of glaze resistance and separation they work very well; but to my eyes they produce an aesthetic disaster. The marks they leave where in contact with pots are pale, anaemic and deathlike, and invariably contrast extremely harshly with the various colours produced by wood-firing. I see them as visually leaving holes in the work.

The next step is to consider the ingredients. Fireclay makes sense. Wads need to have no fusible materials such as feldspars or mica. This precludes low firing clays also because they tend to fuse at high temperatures. Alumina does not necessarily make sense. It is refined and expensive either as alumina hydrate or calcined alumina, and the wads will be thrown away after firing. So cheap is better. My thinking is: what is the cheapest local material I can get? Maybe if I lived in the north of Australia I could try bauxite (alumina ore with some iron impurities) but when I moved to the area where I now live the best looking stuff was sand from a quarry down the road. Simple test — put some in a small unglazed bowl, fire it to cone 10 and see what it does. The local sand does nothing in particular, still looks the same after firing, so for years I have gone down to the quarry with a bucket and shovel and stolen some from the roadside where it spills from the trucks.

Coarse siliceous sand and fireclay make a good woodfire wadmix. The coarse sand leaves a mottled marking on the clay surface under the wad. If the mix is made up using as little fireclay as possible, just enough to hold the wad together when it is squashed slightly in the hand, then after firing the wads will be removed easily because they will be so fragile and crumbly. I hope it is unnecessary to add that siliceous wads are not advisable for salt-glaze firing. If I were still doing saltfiring I would try to get some crude bauxite from some of my friends in the north of Australia to mix with a slightly coloured fireclay (low iron content).

The next consideration is to get a good colour on the exposed clay under the wads, and especially to avoid the dead white colour. Here the selection of fireclay and sand is crucial. I have used Hallam fireclay from a pit near Melbourne for many years (and having published that fact years ago I now note that many other woodfire potters around Australia have begun using it).* This fireclay, apart from being very refractory, is a pinkish colour when fired and diffuses some of its iron onto the pot surface, giving a pleasant pink colour to the wadmark. Unfortunately my original sand gave nothing to colour development so I have been experimenting with others from the local garden supplier. The best looking one is a road gravel, ideal for paths because it has a good particle size grading from dust to 3mm (1/8 inch) so it packs down well. I like the look of its handsome orange colour, with no trace of any fusion, after firing to cone 10- I’ll tell you how it works after the first firing in my new anagama in July. Perhaps I’ll try a few wads in someone else’s firing first. The best feature of this gravel is that it costs Aus$10 per tonne (about US$6 / 4). The second best feature is that it is only available locally so no one else can copy using it. A further bonus is that Barbara can use it for making paths in her gardens.

Other wad materials I have known include flour and sawdust mixed in with fireclay and sand/alumina, One firing I did with Tony Nankervis taught me the perils of flour, which he included in his wadmix. Since my stacking an anagama is slow, taking 4—5 days, the flour starts to decompose and the kiln starts to smell like a reopened massacre burial site. Whatever its advantages I can do without them. I might add that Tony works faster than me.

Sawdust might have the effect of giving some extra reduction under the wads, but carries the disadvantage that it can reabsorb moisture from the air, and will certainly crack raw pots if left too long before firing. The sawdust also makes the wads slow to dry.

An alternative well known to all is using shells. The principle is that calcium carbonate does not fuse to clay, and after firing has been converted to calcium oxide which then combines with water in the air to form calcium hydroxide, which conveniently becomes a powder easily dusted off if left for a few days after firing. Sturdy shells can be used as is: more fragile ones can be filled with fireclay for strength. The main advantage of shells is that gathering them provides the excuse for a day at the beach ‘working’. Their use has become something of a clich unless used creatively. Chester Nealie is a master of this: (I mean that he is creative!! -see Ceramics Technical No. 2 1996 for examples). I like the quality obtained from shell marks when a slip or glaze is applied over them and the work refired. If using large shells, they may be difficult to break in order to use smaller pieces. The trick is to calcine them to about 600C (1100F) to soften them (calcium carbonate does not decompose to CaO until around 870C (1600F). May I suggest that the shells should be clean before you calcine them: or that you leave town for two days to avoid the smell which ranks (yes, I used that word deliberately) with Nankervis’s flour wadding. In retrospect its worse.

Finally but foremost, all parts of the process of wood-firing must fit together into an organic whole when the work is complete. If forms are precise, glazing uniform, all pots stacked in the kiln standing upright, then the wads may well be the neat little round ones placed under the foot. If, as in my work, the clay is crude, the forms erratic, the stacking at all angles and surface deliberately variable, then the wads become a handful slapped on somewhat casually. Not often you see a man in greasy jeans driving a Rolls Royce, or a man in a suit on a grungy Harley Davidson rat bike.

Note – since this article was published the Hallam Fireclay pit has closed. I have stockpiled a 20 year reserve.