PAPER CLAY

I have produced this information resource to explain my approach, the methods I have used and some simple basic information and observations about paper clay.


PROPERTIES OF PAPER CLAY

Paper in the clay changes the molecular structure of the clay body. (The normal structure of clay is small particles, like a lot of balls together. Paper fibres have a vascular structure, which is like a network of long straws, as in a plant or tree from where the paper comes. In plants this vascular system allows water to be carried through these straw like molecules, to the plants leaves. When you add paper pulp to clay the clay particles mix and coat the straw like paper molecules and form a tangled straw network, a much stronger substance. When you add slip to plastic, leather hard or dry paper clay the slip is sucked into the surface via the straws which makes an excellent bond.) The paper burns out of the clay in the kiln after about 300° and then the clay is as normal. So here are a few things paperclay is capable of;
  • You can add wet-to-wet, wet-to-dry, or wet-to-bisque. You can remodel at all stages of making. Paper clay slip is very good joining glue when hand building forms. You can use dried clay rods or even fired paper clay rods as armatures and leave them in the piece.
  • You can work with much thicker walls on sculptural forms. Water vapor and gases will escape through the walls of the artwork more easily because of the paper clay‘s molecular structure, so the threat of exploding is reduced.
  • Paper clay will withstand multiple re-dampening so you can make changes in the form. It will also withstand forced drying. Paper clay has a greater dry strength to the body so moving large pieces is less of a problem.
  • Fired pieces are lighter.
  • Paper clay has better thermal shock resistance. I use white earthenware paperclay for Raku.
  • Glazed pieces can be included into a paper clay piece. I have included fired paper clay pieces into new paper clay work with no cracking.
  • Paper clay can be used on the wheel.

THE CLAY - any clay can be used to make paper clay.

THE PAPER

All types of paper can be used for paper clay, it is always advisable to test any paper you choose, as each paper contains different things which can have different effects on the clay when working with it and on the firing results. For example, some paper contains china clays or borax. Ash from the paper, and borax in the cellulose will act as a slight flux in the clay body. The ash from pieces of paper which fly around the kiln and settle on the work can produce glaze effects at high temperature.

Here are some paper options;

  • Recycle newspaper, small pieces soaked in a bucket of hot water overnight and broken down with an electric mixer the next day to form a pulp. This can be stored in your freezer to stop it becoming mouldy. I like to recycle - it is environmentally friendly.
  • Ready processed and dried recycled paper pulp is my favorite as it is a good time saver, just add water
  • Toilet paper can be used as it is very fine milled paper and is easily broken down in the mixing process. There are some reasons not to use this paper source; Toilet paper contains starch as a sizing material to make it “soft and fluffy”. Starch is a food source for mould when added to the clay mixture; the paper will begin the process of rotting almost immediately. Paper clay made from toilet paper will turn dark gray and start to stink in about-ten days depending on how it is stored.
  • Flax fibres, rag fibres for papermaking etc, these can be blended into the clay.

Newspaper and toilet tissue have a short fibre and flax can have a longer fibre. Short or long fibre it is personal preference, experiment and find out what you like. I like using the flax paper clay it has longer fibres and I feel it is stronger and more flexible/stretchy.


METHODS

In the methods described below I use handheld power tools, please use caution when using them, always follow manufactures instructions when using power tools. When mixing dry ingredients such as the paper or clay, wear a dust mask. When firing paper clay, make sure there is adequate ventilation, a flue on the kiln is advisable or a kiln outside.

All the methods outlined in this information are only guidelines you are encouraged to experiment and adapt the ratios and techniques.

Paper pulp

Soak small news print square in plenty of hot water, preferably over night and when it starts to break down mix using an electric mixing tool or cordless drill with a mixing attachment, around 20 minutes should do it. You can test whether the pulp is ready by putting a very small amount (¼ tsp) into a glass of water and checking for any lumps, it should look like a smooth cloudy mix when held up to the light. You then sieve the pulp to remove some water - it should be the consistency of thick but not sticky porridge.

1 Pulp and slip

The ratio. It is personal choice; I use 1 part paper pulp to 2 parts clay slip by volume and 1-3. This is the recommended starting point the experiments can begin using this as a starting point. If the clay you are using is groggy then you may find less paper better, but I have used a high paper content and grog content and had success, again experiment.

Mix the pulp and clay slip together with the drill mixer bit. The clay is much better the more thoroughly it is mixed.

This mixture can be used straight away, by painting onto paper and cloth structures, each layer can be dried off and more layers applied. A minimum of 3 layers is advisable especially if the paper clay slip is thin.

You can dip stuff into the slip like, paper balls, plant material, fabric, sticks etc anything that can burn out safely in the kiln. When dry these pieces can be stuck together with slip to make a larger structure. Paper cubes and balls make excellent building blocks for large sculptures.

The slip can be spread over a plaster slab to dry and can be pealed of and used in slabs or wedged and used as normal plastic clay.

You can slip cast work with paper clay slip. It may stick to the mould more that usual but if you leave it to dry slightly longer it is fine.

2 Pulp and plastic clay

Make some pulp. You fill a bucket ¼ full with pulp and then add some more water to make the pulp thinner but not too runny, the consistency of thin porridge. Then add any clay body from plastic. Break the clay into small chunks (one inch cubes) and add to the pulp until the bucket is ¾ full.

Make sure not to over mix at this point, one or two turns with a stick and then leave it over night. The next day you can mix it together. The clay should have become soft and sludgy. In this method you need to judge the mixture by eye to see if you need to add more water.

Once mixed, I see how the mixture looks and add more pulp if necessary. Test on small samples and do some test firing to see what results you get.

I like this method it gives a thick past rather than a thin slip, which means you can dry it quicker. You can build up thicker layers when you paint on formers, paper structures or inside of a mould.

3 Pulp, clay powder

Make some pulp. Fill a bucket ¼ full.

Work out how much powdered clay is needed to make a given volume of slip, say ½ a bucket full. This quantity of dry clay can then be added to the pulp mixture. Mix it in gradually with a stick at first, It will start to get a little dry so add some water to enable the clay and pulp to combine well. When the powder clay is incorporated mix with the electric mixer.

4 Powder clay and dry paper pulp fluff

If you have ready dried and fluffed pulp. I have found a good ratio of fluff and powdered clay is about 1 fluff to 4 clay.
Put the two dry materials together in a bucket, mix it in gradually with a stick at first adding enough water to enable the clay and pulp to combine well. When it is wet enough the mixer can be used.

REMEMBER YOU MUST WEAR A DUST MASK WHEN USING POWDERED MATERIAL

MOULD AND STORAGE

Due to the organic content in paper clay it is prone to mould. Mould in paper clay is caused when the mould, which is naturally present in clay, has a food source. Paper and cellulose and especially corn starch is a food source for bacteria and mould. This mould can form in the presence of oxygen and without it. Some paper clay will have mould on the outside and be fine on the inside. Some of this mould only forms on the inside of the ball of clay without oxygen present. Putting a small amount of bleach in a spray bottle full of water and spraying the surface of the clay can correct the outside. The mould will be destroyed. If the clay is white on the outside and black on the inside, you can reprocess the clay with a small amount of bleach in the water. It is always advisable to make batches of clay in the quantity you need to use for any given making session; this avoids having to store it. Don’t store wet paper clay slurry for any length of time the wetter the mixture the more prone to rotting.

If you have to store paper clay this should be done by;

  • plastic paper clay should be wrapped well in plastic and stored in a cool dark place
  • paper clay slip in a bucket with an air tight lid and also stored in a cool, dark place.
  • paper clay can be stored very well as dry scraps or sheets and only needs to be re wetted to use again.
  • Try not to use a clear storage container.

(The paper clay will work fine, if slightly mouldy and when the paper burns out in the kiln the clay colour will be normal. However, it is not advisable to use paper clay that has begun to turn black, other than it being unpleasant to use, there could be a health hazard associated with the mould. The general consensus is that when the paper has gone rotten in the clay this leads to a weakening of the paper fibre and the paper clay no longer retains its special properties. I have not experimented with very mouldy paper clay so I have no personal experience of this.)


EXPERIMENTATION AND OBSERVATION

I have made experiments for my own work and made a few discoveries along the way. I have mixed earthenware and stoneware with great results. I have mixed smooth stoneware and porcelain and made a beautiful body, which is lovely in Raku.

One of the things I do is to make a sculpture from stoneware paper clay at the base and from the mid way point make it with earthenware. I do this because my kiln is hotter at the bottom than at the top.

You can include materials, which burn out of the clay. This enables you to open up the clay even more. Cooked spaghetti or rice can be put into the clay to give interesting textures and in porcelain you can achieve many interesting transparency textures by these additions.

Paper clay can be speed fired once bisqued and crash cooled. I have fired stoneware and porcelain paper clay up to 1300° in 30-40 minuets with a small rocket kiln, which is similar to a round raku kiln fired with gas.

Paper clay is very strong green and very fragile in the bisque stage.

There is a reduction in warping and Shrinkage is less, especially from wet to dry and at low firing temperatures, but with high-fired work, over 1250° there is little difference, on average it is around 1° less shrinkage.

I have found that clay that is well worked, ie. Wedged, rolled and smoothed is much more flexible and strong than a poured slab of clay.

De flocculates like Sodium silicate, increases the amount of clay in suspension enabling more clay to be added to less water and reduces the amount of water to be removed.


READY MADE PAPERCLAY - I use Scava Clays, TS Flax Paperclay. This is more expensive than making your own but it is very convenient and save time. It comes in slip form and plastic, earthenware, stoneware, porcelain and terracotta clay. It lasts for a long time if the seal on the bag is not broken and slightly longer than home made paper clay once opened. This can be bought direct from Scava Clays in Ireland or Valentines Clay in Stoke on Trent. Potclays in Stoke are also producing a paper clay now.


FOR RELATED SITES AND SUPPLIERS CONTACT DETAILS CLICK HERE

BOOKS ON PAPERCLAY

Paper Clay (second edition)
by Rosette Gault
Ceramics Handbook
A&C Black - London
University of Pensylvania Press - Philadelphia

Working With Paperclay and other additives
by Anne Lightwood
The Crowood Press

To buy books on line try
www.amazon.co.uk

 
Tina Neale