Creating texture on inner and outer surfaces of your pottery/Part 1-using a stamp

Clay is wonderfully pliable, which is why I and so many others are so hooked on it. In some of my previous newsletters I have written about using glazes to create colour and pattern. If you want a quick recap you can find these articles in ‘A Potters Journey’ on my blog.

Textured clay works fantastically well with a glaze, no need for expensive or complicated gadgets here, the simplest of found items can be used to create detailed and intricate patterns. All you need is imagination and patience.

The following  technique is widely used and is straightforward,a simple method of creating texture and detail by using a ready-made stamp to emboss the surface. Wooden or rubber print blocks work equally well.  I’ve used a Vietnamese good luck stamp on some of my salad bowls. It wasn’t intended for use on pottery, but I tried it out and loved the result.

A stamp can be applied directly or indirectly to your wares.  Applying a stamp directly can be complicated, and there is a risk of distorting your piece or weakening the wall.  In the case of my Vietnamese stamp, I applied it indirectly.

kit

Roll out a thin slab of clay, turning it over from time to time, so as to prevent it from sticking to the work surface and rolling pin.

roll-out

 

Now cut the clay slab to sizes, enough for a few stamps, dip the stamp into cornflower to stop it from sticking to the clay and roll the clay over it applying slight pressure with your rolling pin or wooden dowel (using talc or other glaze materials for dipping your stamp is fine too and might create some interesting glaze effects).

 

talc

 

Gently peel the slab of the stamp, making sure it doesn’t tear, cut it to size, place it on the pot and gently mark around it.

trace

trim-2

Now put your stamped clay aside, score the area within the markings on the pot and apply slip to it and the back of the stamped clay. Reapply the slab and join it to the pot by very gently tapping it from the centre outwards in all directions. . Be sure that the edges adhere tightly to the surface of the piece, so that the ‘stamp’ doesn’t peel away during drying and firing, remove any excess slip from the edges with a small paint brush or wet finger and carefully smooth the area.

 

cross-hatching-and-slipping

tap-tap

finished

vietnamese-bowl-2

Glazed & confused

The only way to learn about which ceramic glazes work for you is to test them. The idea is to study what happens when you mix various amounts of various ingredients in a glaze and fire them to various temperatures. It’s about understanding how different materials affect each other in order to be able to achieve the results you want, and to troubleshoot when the results are really not what you want.

Sounds confusing? Well yes, and certainly not great for those of us who avoided chemistry at school because, in essence, this is known as ‘glaze chemistry’ which is complex and at times intimidating.

Recently, I was working on blending some new colours into my wares, not just new colours but new applications – white with a yellow stripe, white with a purple stripe and several others. I bought some new commercial stains and glazes in the colours I want, and experimented with them. I tried several glazing tests and methods:

  1. A) Mixing commercial stains into engobes, as I do with colouring oxides.
  2. B) Mixing stains into my own glazes.
  3. C) Using coloured commercial brush-on glazes over my own glazes.
  4. D) Using low-temperature glazes over a high-temperature matt glaze in the hope that they would run down and blend into the base glaze.

So far, I’ve had very limited success with these tests. In general reds do show up, yellows disappear or come out faded at best; and the colours stay put, they do not run down the sides of my pots

I’d like this tale to have a happy ending, but I’ve not yet solved this chemical conundrum. However, I must emphasize that it’s vital to keep all test results. Even if they are not what you’re looking for at the time, this little bit of research may lead you to what you are looking for later on.

Also, my quest for a solution to my glazing problems led me to a website which aims to make glazing chemistry more like glazing cookery, with all recipes tried , tested and available at the click of a button. Who knows – I might be uploading a recipe of mine to this collection quite soon?! http://ceramicrecipes.org

Something about clay

I know some of you wonder whether I spend my free time digging up the back garden to get clay for my pottery. I guess it’s time to get the record straight and give you an insight into clay in general and more specifically the clay I tend to use.
Not quite as exciting as digging up my own clay, I actually order ready-made clay and have it delivered! Even better, if I’m not here when it arrives I leave a key and find it neatly arranged inside the entrance of my workshop when I get back.

‘Clay’ is short for ‘clay minerals’ which are formed over long periods of time by the weathering of rocks, and is often found around large lakes or marine basins. It is a deceptively simple material, cheap and abundant. It is soft, pliant, plastic and impressionable, without grain or direction. It can be modelled, pounded, flattened, rolled, pinched, coiled, pressed, thrown on the wheel, cast into moulds… you name it. It can be made into works of any size and unfired clay can be crumbled, mixed again with water, and made into something else.

Firing clay changes its chemical composition for good, and converts it into ceramic material. Fired clay may be white, creamy, red, orange, yellow, grey, brown, black, speckled, streaked, translucent, textured or smooth, porous or dense like hard stone.

There are three main types of clay – earthenware, stoneware and porcelain. The difference is in their firing temperature, the strength of the fired material, its colour, density, or translucence.
Earthenware is low fired (up to 1100 degrees centigrade) and can be quite porous.
Stoneware is high fired (1200-1300 degrees centigrade), is vitrified, and can be as dense as hard stone.
Porcelain is usually dazzling white and contains elements of glass in its composition, it is normally used thin, is high fired, and can be translucent.

As I have mentioned before, most ceramicists buy ready-made clays, packed as clay bodies – blends of natural clays ready to use and suitable for practically any specification, i.e colour, plasticity, texture, strength, firing range and many others.

I use stoneware clay bodies made in Europe. I prefer darker iron-bearing clays for use with my blue glaze – that’s how I obtain depth of colour; bright clays with less iron for my whites – that’s how I get a clearer colours.