Vitracolour Stain - Intense Red

Adding stains to Glazes and slips.

A small percentage of a stain (1 to 10%) can be added to a transparent or opacified glaze (a white glaze) to make coloured glazes. In the making of a slip, we would recommend using a ball clay called Hyplas71. The more stain added the more intense the colour but don’t add more than you need, as that increases the risks with health and safety. See our example photographs and suggestions. It is very important to test with your chosen host glaze as some glazes might not be compatible or they can affect the colour.

We have used these stains using our Vitraglaze range of transparents and zircon (a form of Zirconium Silicate) based whites, earthenware zircon white and stoneware polar white.

Method

We would suggest making a small amount and testing it with your chosen clay body. Applying it to a white clay will produce the brightest colour.

A simple way to test, use 100 grams of your chosen glaze as a powder, add the percentage of stain dependant on strength (see our recommended percentages for each colour). For example, for a pale yellow we would add 2% which is 2g and add 75g of water. You can sieve this in a 100# mesh test sieve but as our test was so small, we didn't sieve. For bigger quantities we would highly recommend sieving your mixture. Once you’ve mixed your test amount you can dip a small clay sample, re-dip 2 to 3 times and fire to the temperature of the glaze you are using. Increase the percentage of stain. We used for the majority 2%, 4%, 6%, 8% but some stronger colours, dark blue and dark green we used .5%, 1%, 3%, 5% and repeat the above. Don’t forget to label your swatch with an underglaze pencil.

For some colours indicated we have used stain enhancer at 2% (2g for the test) of the dry weight of the powder. This improved micro bubbling in the glaze and colours seemed brighter too.

If you wish to be more scientific in your testing follow the digitalfire document for a more organised and precise method. 

In a decorating slip, we had success with the stain added to the ball clay (hyplas71) and mixed with water. This was then put onto dry greenware, fired to bisque and then glazed fired with a shiny transparent, to bring out the colour.

Vitracolour Chestnut Stain - Decorating Slip

Making coloured clays.

You might want to make a clay a certain colour and this is possible with stains. But note, some colours may affect the way a glaze works with the clay body. Blue stains have a modified cobalt in them which can affect the melt temperature of the clay. Using white body clays will be the best choice but many advocate porcelain.

Method

A stain can be added to wet or dried clay. The later will provide a more even colouring. Dry the clay out by putting small lumps on a plaster batt, then crush it in a bag with a rolling pin. Mix a percentage of the stain into the powdered clay but do not crush the stain. For a test amount you can take 10 grams of dry clay, add the percentage of stain that you want to test and mix them. Add small amounts of water to get a plastic consistency, then mix the clay in your hands into a workable putty. Make sure you protect your shelves and kiln.

For advice on mixing stains with wet clay follow this article from The Pottery Wheel.

You could try colouring casting slips using our white earthenware and white stoneware, test as above, although you will need larger quantities for example 1kg slip powder and a small test mould.

Using stains as an underglaze.

When using a stain as an underglaze you would need the addition of a flux. We have called it ‘underglaze frit’. We suggest a ratio a ratio 4 parts stain to 1 part flux. Using a medium called ‘Vitraglaze Mixing Medium - Pehatine’, it will give an opaque flat colour, if used with just water it will give a washed affect. Traditionally underglazes were painted onto bisque-ware then overpainted with a shiny transparent glaze and then fired once more. It can be left without a glaze for a matt finish.

Having tested the colours with the ‘Pehatine’, the painting experience was better than any other premade underglaze we have ever used. 

Method

We used a stainless-steel bowl, put in 4.8g of stain and then added 1.2g of the underglaze frit powder. We then used a dry mixing brush to mix it thoroughly. We then used the equivalent amount in volume (a teaspoon) of the ‘pehatine’ neat from the bottle, then mixed it up using a medium firm brush. If you are making a significant quantity, you should then sieve with a 100# but with this small amount in a bowl we can see any agglomerated powder. You will see and feel how creamy and smooth this underglaze is, but do not be tempted to overpaint and build up layers however nice the experience. As a too thick underglaze with a glaze can impede the breathing of the clay in the firing process.

Hand painting with a stain onto an unfired glazed surface.

If you have glazed a pot but not yet fired it, you can paint on that surface with a stain. We have tested a stain with just water, a stain with neat pehatine and finally a stain with the underglaze frit and pehatine (essentially an underglaze). All of these onto a buff clay body, pre-fired to a bisque of 999, with a Vitraglaze Tin White Speckle brush-on glaze, applied a little time before. This was then fired to 1240 on a fast climb.

Painting stains on an unfired white glaze is almost a majolica technique, although in the old days they would have used a stain with a little clay and water.

The painting experience of the stain and water on the left, was a little difficult. The colour dragged as the water was absorbed into the underlying glaze. The colour itself was a little washed out. The fired result revealed the qualities of the blue stain. This as mentioned before is because the blue contains cobalt which behaves like a flux, therefore it worked. The red and yellow stain are more refractory and therefore behaved badly on the glaze, the yellow for instance bubbled off. The violet was more successful but not as good as the blue.

The middle test cylinder in each picture had pehatine added to the stain which was a joy to paint with and the result was a successful glaze fit, however it did have a little mottling like a salt glaze. The last test was the underglaze mixture which painted beautifully and had the best result. The stain had achieved a flat surface, nice and uniform with the underlying glaze producing a glossy surface.