Stain Glass with Silver Nitrate
What is it?
Silver nitrate is used to stain glass and was discovered in the early 14th
century. It is composed of silver nitrate and gamboge gum and comes in various hues, from pale yellow to rich amber. It differs from paint and enamels because during firing a chemical process takes place, in which the stain becomes part of the molecular structure of the glass, rather than adhering to the surface.
Things to remember before you even start to stain glass …
If you are painting and staining the same piece of glass, painting must be done first and fired before staining takes place.
Why? Because stain fires at between 550-560° C – 100° C lower than paint.
- Stain is applied on the opposite side to the paint.
Why? Because stain permeates the glass and is prevented from doing so if paint is already fired onto the surface.
Also, if over-fired, the stain glass can ‘metal’, causing an unpleasant iridescent bloom visible in reflected light. This can be etched off as a last resort.
Test firings
The colour of the fired stain is very unpredictable. It is always a good idea to do stain tests if you require a particular shade or hue. Some glass resists stain almost completely.
There are four main elements that influence colour results:
- the temperature the stain is fired at in the kiln
- the amount of time the firing cycle takes
- the thickness of application
- the type of glass used
Equipment needed
Silver stain, water, palette, palette knife, badger, mop and various brushes.
Application
Just before applying stain it is helpful to dampen the glass or lightly wet the tips of the badger brush. This gives you more time to manipulate the stain before it dries and prevents hard edges.
Stain can be applied directly with a brush, or blended with a badger like paint. You can create dark and light areas by blending from thick to thin respectively. You can use a variety of brushes and tools to apply the stain directly, depending on the marks and textures you are aiming for.
Cleaning
Always clean brushes immediately after stain use. The stain is corrosive and will start to destroy the ferrules of brushes and palette knives if left.
Firing
Stain fires between 550-560 degrees C.
If it is fired more than once, stain intensifies in colour. Unfortunately, this doesn’t mean that if a piece of glass is resisting stain, that repeated firings will solve the problem.
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