Firing is where a printed decal becomes a permanent decoration, and where most problems on a new setup come from. The good news is that the rules are few and the same for every kiln.
Firing ranges by INEQS set
| Set | Range | Typical ware |
|---|---|---|
| Unfluxed red R101 | 860 to 1,150 °C | Porcelain, stoneware, glazed tile |
| Unfluxed magenta M40 | 860 to 1,000 °C | Porcelain, stoneware, glazed tile |
| Fluxed magenta MM40 | 820 to 900 °C | Onglaze porcelain, enamel |
| Fluxed red RR85 | 805 to 830 °C | Onglaze porcelain, enamel |
| Glass toner sets | 540 to 630 °C | Float and borosilicate glass |
These are general guidelines. Your glaze, kiln and ware can shift the optimum by tens of degrees, which is why INEQS supplies a curve with each set and tests customer ware before production.
A standard curve
- Dry. After applying the decal and squeegeeing out the water, dry the piece for about an hour at 40 °C. Trapped water boils in the kiln and lifts the decal.
- Heat slowly with ventilation to 420 °C. The covercoat and toner carrier burn out in this phase; the kiln must be ventilated or the fumes will mark the surface. Around 100 to 150 °C per hour is typical.
- Close and climb to peak. Once past about 420 °C, close the vent and rise to the peak temperature for the set.
- Short hold, then cool naturally. A few minutes at peak is enough; longer holds burn out reds. Cool with the kiln closed.
Common faults and causes
- Bubbles or pinholes: water left under the decal, or heating too fast through burnout
- Reds fired brown: peak too high for the set, or magenta set used where a red set was needed
- Colour weak or washed: peak too high, hold too long, or developer worn in the printer
- Decal edge visible: fluxed covercoat on a partial area; cover the whole area or use lacquer with a fluxed set
- Grey haze on the surface: no ventilation during burnout
Kiln requirements
Any electric kiln with a programmable controller that reaches your set’s range. Even heat matters more than size; test a piece in the coolest and hottest spots of a new kiln before a production run. INEQS supplies kilns on request.