How do I fire digital ceramic decal transfers?
Kiln Temperatures are not all equal!
Have you noticed how ceramic colours fired on one kiln at a set temperature may differ from another kiln fired to the same temperature?
The amount of heat treatment that the ceramic is subjected to can vary, even if kilns are set to the same temperature. Heat treatment is a combination of time and temperature, but a large densely packed kiln will generate more heat energy at a given temperature than a small kiln. A further complication is added by the accuracy of the kiln’s temperature controller and ‘overshoot’ where the kiln temperature continues to rise even after the heating elements are switched off. The latter is more common in small kilns running on a fast firing cycle.
The recommended firing temperatures set out below are only a guide and if you’re using a new firing cycle for the first time then a ‘test firing’ should be performed to check out the results. If the colours are weak after firing, then you’ve probably fired it too high.
Recommended firing temperatures for ceramic decal transfers
Header | Ramp 1 | to | Ramp 2 | to | Soak |
|---|---|---|---|---|---|
Standard Set | 100°C per hour | 300°C | 300°C per hour | 800-850°C | 20 Minutes |
Red Toner set | 100°C per hour | 300°C | 300°C per hour | 780-800°C | 5 Minutes |
Fused Glass | 100°C per hour | 300°C | 300°C per hour 300°C per hour | 660-720°C | 5 Minutes |
Enamel Ware | 100°C per hour | 300°C | 300°C per hour | 720-780°C | 5 Minutes |
In-Glaze Set | 100°C per hour | 300°C | 300°C per hour | 1050-1100°C | 30 Minutes |
How temperature stable are the ceramic toner colours?
You’ll be aware that the colours of ceramic toners don’t develop until the transfers are fired. Ceramic colours are made up of a mix of metal oxides which are stable at high temperatures but some colours are more stable than others when fired. The red toner for instance is the least stable of all the ceramic toners and will burn away if the kiln reaches temperatures in excess of 820°C. The magenta toner will similarly fade as the kiln reaches 880°C. If you notice a loss of colour on firing it’s likely that the ware has been subjected to too much heat! Cyan and black are the most stable colours and will remain after the red, magenta and yellow have burnt away. If you need to fire in-glaze then higher temperature stable versions of all the colours are available.
What happens during the firing of ceramic toner?
Ceramic toners consist of the ceramic colour, a flux and a resin. The resin is a thermoplastic material which serves to bind the toner to the paper when it passes through the fuser. A further plastic ‘covercoat’ layer is subsequently applied to the print, which serves as a carrier when the decal is separated from the decal paper.
During the firing process any residual water or solvent will be vaporised first followed by the organic material present in the gum, resin and covercoat. At around 300°C the majority of this organic material will have been driven off leaving the powdery colour on the surface. It is often recommended that this first part of the firing process is undertaken using a slow ramp in order to minimize any disruption caused by the burn off. After the organic material has been removed the firing can then proceed at a faster rate to the end of the cycle. The flux present in the toner will melt during the latter stages fusing the colour to the ceramic. If fusing onto glass then the colours will be absorbed into the glass as it reaches its softening temperature. A similar effect will occur when in-glaze toners are fired above the softening point of the glaze.
What is the purpose of the kiln soak?
The soak is the amount of time the kiln is held at a set temperature. Holding at the peak temperature for a period will help the colours to develop and fuse to the glaze or sink in on a glass fire.
We hope this answered some questions, If you need any more information please comment below.
