Prometheus Mini Kiln PRO-1 PRG

prometheus kiln chamber

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).

Construction

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.

Specifications:

  • 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.

Chamber

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

Programmable Controller

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.

Hold Time

  • 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.

Next Setpoint

  • “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.

Run

  • “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.

Conclusion

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).

Further Reading

  • Prometheus Hobby – manufacturers website where you can download the full operating manual as a pdf and where you can access the CE certificate.

prometheus kiln chamber

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.

silver soldered brass parts

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.


enameled bowl

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.

About Nigel 384 Articles
I've been making models since I was around 7 years old and using a lathe from the age of 11, a self taught engineer with a passion for making model engines.

5 Comments

  1. Hi Niel,thanks for the review, I was mainly looking for cost of running per hour and whilst u (rightly) had variations it was enough for me to know I can run it for several hours with getting a bank loan ps have to agree with previous advice re silver soldering, I have only ever used a torch for that. Anyhoo thanks again for the info.

  2. The poor silver-soldering is not a fault of the kiln, but incorrect choice of technique. The heating needs to be rapid and thorough, and removed as soon as the solder has flowed fully. Otherwise first the flux will spoil, then with continued heating the solder can dissociate. You might get away with it if the kiln is brought to temperature before putting the metal in, and furnace-brazing is used industrially, but otherwise for our model-making, a kiln is better for heat-treating metals than joining them.

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