Prometheus Mini Kiln PRO-1 PRG is a small electric kiln of 700W and able to reach 1000°C. The chamber is small at 115 x 130 x 70mm but very usable. The real beauty of this for me as a model maker is the ability to heat treat small metal parts as this kiln has a programmable controller. This particular one I bought from Cookson Gold (£425 as of January 2021).
The main case of the kiln is rather well made and painted.
The hinge is a fairly standard door hinge, but with a small door this is a substantial hinge. The door latch is the simple sprung balls that clamp a tag. This is not so great, but the springs are adjustable so I can increase the force.
- Maximum firing temperature of 1000ºC
- Four button digital temperature control and display
- 9 programs and 5 segments in each
- Cool-touch handle, 90° opening door
- Well ventilated, powder coated exterior casing.
- Heating elements : 4; top, bottom and sides
- 220V operating voltage, 3.2A, 700 Watts
- Total weight 5.7kg.
The chamber is quite smooth in finish with a temperature probe that protrudes into the chamber at the top. Do note that you should not place items directly onto the chamber floor, either use a shelf (sold separately) or a mesh that has bent edges to elevate any items away from the floor.
Chamber dimensions are:
- Width = 115mm
- Depth = 130mm
- Height = 70mm
Don’t be daunted by the number of programs and steps as this controller is easy to use. The instructions for programming the kiln are available as a pdf at CooksonGold:
- When the kiln is turned on, the display will flash with the message “IDLE”. This means the kiln is ready to program.
- Press the “PROGRAM Start/Stop” button to select a program. “PrO” will appear on the display.
Press “PROGRAM Start/Stop” again to select this program.
- you can change the program number with the increase/decrease buttons before then pressing “PROGRAM Start/Stop” to select
Temperature Rate of Increase °C/hour
- “Ra1” will appear on the display. This is asking you to input the rate at which you would like the
kiln to heat up, in degrees per hour. For example, you can choose to bring your kiln up to
temperature over the course of several hours, or over the course of just a couple of hours.
- you can toggle around to “FULL” and this will heat the kiln as fast as possible.
- note: if you hold the increase/decrease buttons for a length of time the rate that the numbers increase or decrease will speed up
- To work out the initial heating rate, take the temperature you would like the kiln to reach and take
away the current room temperature. Then divide this number by the number of hours you would
like the kiln to heat up over. For example, a desired temperature of 900°C over 2 hours, when
room temperature of 20°C, would be a rate of 440 (900-20/2). Use the up and down arrows to key
in the rate number. Press “PROGRAM Start/Stop” to confirm.
Temperature Set Point
- Tc1 will show in the display. This is the final temperature at this ramp rate. This will be in °C or °F depending on your preference (this is shown by a small LED illuminated against the selected unit.
- HLD1 will show on the display. This is asking you to input the firing time – how long to keep the
kiln at your chosen firing temperature. A dot has now appeared between digits 2 and 3 on the
display, specifying hours and minutes. Press the up and down arrows to select your chosen
amount of time. Press “PROGRAM Start/Stop” to confirm.
- “Ra2” will appear on the display. This is asking you to input a second heating rate, or a cooling
rate, if desired. This is typically used for more complex firings such as ceramics, where more than
one temperature is required during firing (i.e. a lower temperature followed by a quick burst of a
higher temperature, or a higher temperature followed by a lower temperature). Up to 5 different
temperatures can be set to run in succession during one firing, and “Ra2” to “Ra5” simply run
through steps 3-6 again in order to choose different heating/cooling rates, firing temperatures and
firing times. For most jewellery purposes, these options are not needed, so just press
“PROGRAM Start/Stop” to confirm the program.
- “Strt” will now appear on the display. This is asking you if you wish to start firing. Press
“PROGRAM Start/Stop” to confirm, and your program will begin.
- If you wish to stop the firing part way through, simply press the “PROGRAM Start/Stop” button
again to abort the firing.
Overall the Prometheus Mini Kiln PRO-1 PRG is proving to be rather excellent. A well made, easy to program kiln that runs from a normal mains socket. Being 700W and small it will be reasonable on running costs as at most it will use 0.7kWh per hour of use and at roughly 14p/kWh that is roughly 9.8p / hour (but this can be lower at night eg down to 9p/kWh and as high as 20p/kWh, so gives a range of 6.3p / hour up to 14p / hour).
- Prometheus Hobby – manufacturers website where you can download the full operating manual as a pdf and where you can access the CE certificate.
I had a go at using the kiln to silver solder using the easy silver solder paste. This paste includes flux.
However, I programmed the kiln to ramp up to 720°C and hold there for a minute. The issue I found was the joint had not been formed and the solder was like grit. I think it had dried out in the ramping up stage. I will experiment further.
The next level of experiments using traditional silver solder and flux has worked rather well.
OK, this was the 3rd experiment, but the result is rather neat.
A first go at enameling – using the Prometheus Mini Kiln PRO-1 PRG I made simple enameled copper bowl.
This is quite a naïve part, but got me over the initial barrier of basics steps required to enamel copper.