Workshop – Glaze inductionPosted: June 13, 2014
Today we had an induction into using glaze with ceramics, which is something I have been interested in for a long time but never gotten the chance to explore.
If we want to access clay, the clay store is open Monday 11:30-12, Wednesday 2-2:10, and Thursday 11:30-12, and there is 9am-5pm access to the glaze room. If you want to book a kiln there is a meeting every Friday at 12, and you may only book one test kiln a week per student. (this is more for my own personal notes in case I forget in future)
When mixing your own glazes it is important that you label your glaze with the correct stickers indicating whether it is an irritant or poisonous, or both, as well as the recipe of the glaze. This is in case there is some form of accident, for example someone ingesting your glaze, and the paramedics will be able to easily find what the ingredients were.
It is important that when storing glazes, they are not kept in a powder form. They must always be kept in a liquid state with water, and always in a sealed jar or container. This is to prevent the powder escaping as a dust and being inhaled, which can cause damage to the lungs. When mixing glaze you should also be aware to always where a respirator so as not to inhale any dust that is in the air.
If you are using Fritz in your glaze, keep in mind that it is very unstable and what is known as a “raw glaze”, and should be mixed with clay and flux in order to make it usable. When mixing glazes, a good starting point is 100g of glaze to 100ml of water for earthenware or 100g to 80ml for stoneware, although you might want to change these rations accordingly if making a thicker or more watery glaze. Once your glaze is mixed, you must then pass it through a mesh in order to sieve out any unmixed sediment and ensures that the glaze is even. To do this you should use an old paintbrush to push the glaze through the sieve, and ensure that none of it is wasted, as this could throw off your ratios and have an undesirable effect on the outcome of your glaze.
When applying the glaze to the object it can be brushed, sprayed, or sponged on, and you should be sure to glaze the entire body of an object as leaving unglazed areas will create an uneven tension which can result in cracks. When glazing earthenwear your glaze only needs to be 0.5-1mm thick, however stonewear should be 2-3mm. If you are glazing a cup or a vase, it is important to glaze the rop rim well as the glaze will shift during firing as it becomes more fluid, and to leave the rim on the base unglazed so that it doesn’t become stuck to the firing shelf in the kiln. After being glazed the object should be left to dry overnight before being fired.