Glazing Pottery: Important Tips
A glaze is a distinctive type of glass coating which is usually formulated chemically to stick to the surface of the clay, or melt into the body of the clay when fired. Basically, pots are glazed to make them look colourful, water-resistant, easy to clean and durable.
The vital ingredients used for glazes are silica, which is the glass forming element; flux, which supports the melting of the glaze; alumina, which is added to preserve the glaze and make it less liquid and more robust; and oxides, which add color to the pot.
Mixing And Glazing Pottery
When mixing and spraying glazes, it is important you wear a mask, because as the dust rises from the powder, it can become harmful. It is very necessary and required that anyone working with glaze puts on a mask at all times. Gloves and eye protection also come highly recommended.
It is very important to completely mix a glaze by adding water, as the chemicals are likely to descend overtime. If the glaze is not properly and completely mixed, there is no guarantee that you will get the same surface quality, colour, or the glaze will even stay on your pot during the firing process. In addition to this, if it’s not completely mixed, you could even change the preparation of the remainder of the glaze in the bucket and ruin the glaze for the next person. This could be one possible explanation for why some glazes work well for a time and then don’t work at all! To ensure that the glaze is mixed properly, use a spatula, whisk, or electric drill mixer to carefully mix the glaze.
There are different types of glaze, below are some of them:
Matt – having a gloomy or unpolished surface
Opaque – displaying opaqueness, hindering the passage of beaming light
Gloss – radiance or sparkle caused by reflected light
Transparent – this is the property of conveying light, so that colors or textures lying underneath are clearly visible.
Steps In Glazing
The following steps are usually followed in glazing:
- Ensure that your pots are clean and dry. If possible, wash the pottery and allow it to dry.
- Make sure you tape the base, or any part of the pot that may likely touch the shelf.
- Glaze the inside of the pot first, then glaze the outside.
- If you want to use a second glaze over the first, make sure you wait for the first glaze to dry
- Make sure you use your finger to smooth any cracking or pin holing of the dried glaze surface
- Put the glazed pot on the glaze firing shelf for final firing in the kiln
- Do not forget to keep record of glazes used, clay colour, shape of the pot, and notes on your glazing process
- If you’re unsatisfied with your application of the glaze, wash it off carefully and allow to dry for 24 hours before applying the glaze again.
This refers to painting ceramic colours or glazes over a glazed pot and blending them on the ware when fired. Remember: when putting a second glaze over the first glaze, wait for the first to dry.
Quite a number of ornamental glaze effects can be completed by covering segments of a piece with wax-resist or covering off areas with tape, stencils or paper so that the core area will remain observable.
- Always ensure you mix with mask, gloves and eye protection.
- Students should make sure they ask a member to mix if supply is worn-out.
- All glazes with high proportions of oxides are toxic when used as food containers.
Mason Stains And Under glazes
You can apply under glazes to green-ware or bisque ware before the firing process. If it’s on un-fired clay, any Mason stain combined with porcelain slip can be used as a pigment. Make sure you mix to the desired colour by eye and to the uniformity of thick cream.
Prior to any glaze application, Mason stains should be bisque fired. Some Mason stains properly mixed in water can be used in a similar way as an oxide wash without necessarily being bisque fired first.