Prometheus Kilns FAQ & Troubleshooting

This guide covers all Prometheus kiln models: Pro1, Pro1T, Pro1PRG, Pro7, Pro7PRG, and Pro7PRG-BD. It is intended for hobbyists, semi-professionals, and professionals using their kiln for metal clay firing, enamelling, and glass annealing.

 

 

PART 1 — FREQUENTLY ASKED QUESTIONS

 

 

Q: What can I use my Prometheus kiln for?

Prometheus kilns are multi-functional hobby kilns designed for a wide range of creative applications, including:

•       Metal clay firing — silver clay, gold clay, bronze clay, copper clay

•       Enamelling on metal

•       Small ceramic works

•       Glass fusing, glass slumping, and glass bead making

•       Glass annealing (including torch-work bead annealing)

•       Annealing and hardening of silver, gold, and other metals

 

Q: Which Prometheus kiln model is right for me?

Prometheus offers two kiln sizes and three controller types. Here is a quick overview of all models:

 

Model	Chamber Volume	Max Temp	Controller	Special Feature
Pro1	1.1 litres	1000°C	Basic (target temp only)	—
Pro1T	1.1 litres	1000°C	Target temp + hold timer	—
Pro1PRG	1.1 litres	1000°C	Programmable (15 programs × 5 steps)	—
Pro7	7.3 litres	1150°C	Basic (target temp only)	—
Pro7PRG	7.3 litres	1100°C	Programmable (15 programs × 5 steps)	—
Pro7PRG-BD	7.3 litres	1100°C	Programmable (15 programs × 5 steps)	Bead Door for glass annealing

 

Choose the Pro1 series (1.1 litre chamber) if you work with metal clay, enamelling, or small glass pieces and need a compact desktop kiln. Choose the Pro7 series (7.3 litre chamber) if you work with larger pieces, need to fire multiple items at once, or want more versatility.

For the controller: the basic Pro1 / Pro7 is ideal if you fire at a single fixed temperature. Choose the Pro1T if you need an automatic hold-time timer. Choose a PRG model if you want to save and recall multi-step firing programs for different materials or techniques.

 

Q: What is the Bead Door on the Pro7PRG-BD?

The Bead Door (BD) is a small, dedicated opening on the front of the Pro7PRG-BD kiln. It allows lampworkers (torch artists) to slide hot glass beads into the pre-heated kiln for annealing without having to open the main kiln door. This maintains the annealing temperature inside the chamber and reduces thermal shock to the beads. The Pro7PRG-BD is the recommended model for flameworking / lampworking studios.

 

Q: What are the technical specifications?

Pro1 / Pro1T / Pro1PRG:

 

Specification	EU / UK	US (North America)
Voltage	220 V	110/120 V
Power	700 W (3.2 A)	800 W (6.67 A)
Maximum Temperature	1000°C	1000°C
Inner Dimensions (W × D × H)	11.5 cm × 13.0 cm × 7.0 cm	11.5 cm × 13.0 cm × 7.0 cm
Outer Dimensions (W × D × H)	22.5 cm × 22.0 cm × 28.0 cm	22.5 cm × 22.0 cm × 28.0 cm
Weight	5.7 kg	5.7 kg

 

Pro7 / Pro7PRG / Pro7PRG-BD:

 

Specification	EU / UK	US (North America)
Voltage	230 V	110/120 V
Power	1950 W (8.2 A)	1950 W (17.7 A)
Maximum Temperature	1150°C (Pro7) • 1100°C (Pro7PRG, Pro7PRG-BD)	1150°C (Pro7) • 1100°C (Pro7PRG, Pro7PRG-BD)
Inner Dimensions (W × D × H)	23.0 cm × 20.5 cm × 15.5 cm	23.0 cm × 20.5 cm × 15.5 cm
Outer Dimensions (W × D × H)	36.0 cm × 37.0 cm × 43.0 cm	36.0 cm × 37.0 cm × 43.0 cm
Weight	22.0 kg	22.0 kg

 

 

 

Q: What are the electrical requirements?

Prometheus kilns are available in three versions to match the electrical standards of your region:

•       EU plug — for continental Europe (220–230 V)

•       UK plug — for the United Kingdom (240 V)

•       US plug — for North America (110/120 V)

Pro1 series kilns draw 700 W on EU/UK (3.2 A) and 800 W on US (6.67 A). Pro7 series kilns draw 1950 W (8.2 A on EU/UK; 17.7 A on US). We strongly recommend plugging your kiln directly into a dedicated wall outlet. If you must use an extension cord, use a cord that is no longer than 5 metres and no thinner than:

•       3 × 0.75 mm² for Pro1 series kilns

•       3 × 1.5 mm² for Pro7 series kilns

A longer or thinner cord can cause voltage drops that prevent your kiln from reaching the desired temperature.

 

Q: Where should I place my kiln?

Choose a dry, well-ventilated space. Follow these guidelines:

•       Keep the kiln at least 30 cm away from walls, curtains, window frames, and all combustible materials.

•       Do not allow the room temperature to exceed 40°C. Use air conditioning or a fan if necessary.

•       Place the kiln on a fireproof plate of approximately 50 × 50 cm. Although the kiln base does not become dangerously hot, this provides a safe surface on which to rest hot items removed from the kiln.

•       Keep the power cord away from hot kiln surfaces.

 

Q: Is my kiln safe to use indoors?

Yes, Prometheus kilns are designed for indoor studio and workshop use. Ensure adequate ventilation — especially during the first few firings (new kilns emit a harmless but noticeable odour from insulation bonding materials), and when firing materials that produce fumes, such as certain enamels. Do not use the kiln in a room occupied by people with respiratory health conditions.

 

Q: Should I save the original packaging?

Yes, we recommend keeping the original carton. If you ever need to transport your kiln to a workshop, seminar, or for factory service, the original packaging provides the best protection. If you no longer have the carton, transport the kiln with the door facing upward on a soft, padded surface, supported at the sides to minimise vibration.

 

 

 

Pro1 and Pro7 — Basic Controller

 

Q: How do I set the firing temperature on the Pro1 or Pro7?

Follow these steps:

1.    Turn the switch to the DISPLAY position. The upper display shows the current kiln temperature; the lower display shows the currently set target temperature.

2.    Press and hold the MODE key for 2 seconds until you see “SU” on the display.

3.    Press the LEFT arrow once. One digit of the target temperature will begin blinking.

4.    Use the UP and DOWN arrow keys to change that digit.

5.    Press LEFT arrow to move to the next digit and repeat.

6.    When your target temperature is set, press and hold MODE for 2 seconds to confirm and exit.

7.    Turn the switch to the HEATER position. The kiln will begin heating to your target temperature.

 

Pro1T — Temperature + Hold Time Controller

 

Q: How do I set the temperature and hold time on the Pro1T?

Follow these steps:

8.    Press and hold the SET key for 2 seconds. The lower display shows “H.Set” and the upper display shows the current target temperature.

9.    Use the UP and DOWN arrow keys to set your desired firing temperature.

10.  Press SET once. The display now shows “t.set” (hold time).

11.  Use the UP and DOWN arrows to set the desired hold time in hours:minutes format (e.g., 00:10 for 10 minutes, 01:30 for 1 hour 30 minutes).

12.  Press SET once more. Your settings are now saved.

13.  Turn the switch to HEATER. The kiln will heat to your target temperature, hold for the set time, and then automatically shut off.

 

Q: How do I keep the Pro1T firing continuously without a timer?

Set the hold time (t.set) to a very large number — for example, 90:00 (90 hours). The kiln will maintain the target temperature indefinitely until you manually turn it off.

 

Q: What does the RESET button on the Pro1T do?

Pressing RESET for 3 seconds restarts the hold-time countdown from the beginning and causes the kiln to resume heating to the target temperature. This is useful if you want to run another full hold cycle without reprogramming.

 

Pro1PRG, Pro7PRG, Pro7PRG-BD — Programmable Controller

 

Q: How does the programmable controller work?

The programmable controller allows you to store up to 15 complete firing schedules (programs) in memory. Each program can have up to 5 steps. Each step defines three values:

•       Rate (rA): The speed of heating or cooling in degrees per hour. Use “FULL” for maximum speed.

•       Temperature (°C or °F): The target temperature for that step.

•       Hold Time (HLd): How long to hold at that temperature, entered in hours:minutes (e.g., 01.30 = 1 hour 30 minutes). Enter 00.00 for no hold. Enter 99.59 for an indefinite hold.

A cooling step is created automatically when you set a temperature lower than the previous step.

 

Q: How do I create a new firing program?

From the IdLE display:

14.  Press the PROGRAM button. The controller shows the last used program number (PrO1 to PrO15).

15.  Press INCREASE to scroll to a different program number if desired, then press PROGRAM to select it.

16.  Enter the values for each step: Rate (rA), then Temperature, then Hold Time. Press PROGRAM after each value.

17.  After your final step, set the Rate (rA) of the next step to 0000. This tells the controller the program has ended.

18.  The display shows “Strt”. Press PROGRAM once more to start the firing.

 

Q: How do I recall and run a saved program?

From the IdLE display, press INCREASE to scroll to the desired program number (PrO1–PrO15). Press DECREASE/REVIEW to automatically load the program and review its steps. At the end of the review, the display shows “Strt” — press PROGRAM to start the firing.

 

Q: What do the display codes mean on PRG models?

Status codes (normal operation):

IdLE  — Ready mode — no firing in progress.

DELA  — Delay start countdown is active.

Strt  — Final prompt before starting a firing.

-On-  — Firing has started (shown for 5 seconds).

StOP  — Firing was stopped early.

CPLt  — Firing completed successfully.

VEr 1  — Controller software version (shown briefly on startup).

bAdP  — Invalid program — no Rate value has been entered. Re-enter the program.

 

Q: Can I switch between °C and °F?

Yes. Press and hold the INCREASE button for 20 seconds until “OP-S” appears. Press DECREASE once to reach “Tc-T”, then press START/STOP to enter the setting. Set to 0000 for °C or 0001 for °F. Press START/STOP to confirm. If the small decimal point light in the bottom-right corner of the display is lit, the controller is in °C mode.

 

Q: Can I use the Delay Start feature to schedule a firing in advance?

Yes. From the “Strt” prompt, press DECREASE/REVIEW to access the delay setting (dELA). Use INCREASE/DECREASE to set the delay time in hours and minutes (up to 99 hours 59 minutes). Press PROGRAM to confirm. The kiln will count down the delay period and then begin firing automatically.

 

Q: Can I adjust a program while the kiln is already firing?

Yes. PRG models allow several adjustments during an active firing, without stopping:

•       Skip Step: Press INCREASE until “SStP” appears. Press PROGRAM, enter the step number to skip, and press PROGRAM again.

•       Add Hold Time: Press INCREASE until “HLDx” appears. Press PROGRAM to add 5-minute increments to the current hold time.

•       Change Temperature: Press INCREASE until “CHGt” appears. Press PROGRAM to adjust the current step’s target temperature.

•       Threshold Alarm: Press INCREASE until “ALAr” appears to set an audible alarm for when the kiln reaches a specified temperature. The kiln continues firing normally after the alarm sounds.

 

 

 

Q: Can I place pieces directly on the kiln floor?

No. Always use a ceramic firing shelf, alumina tray, or similar ceramic support between your work and the kiln floor. Direct contact can contaminate the ceramic lining and damage the embedded heating elements. Always use long tongs when placing or removing items.

 

Q: When is it safe to open the kiln door?

Always turn the kiln to OFF before opening the door. Put on heat-resistant gloves and protective eyewear. Work quickly — do not leave the door open longer than necessary. Excessive heat loss through the open door can discolour the painted surfaces around the door opening. Avoid opening the door above 780°C.

 

Q: How do I unload my kiln safely?

•       Turn the kiln to OFF.

•       Put on protective glasses and heat-resistant gloves.

•       Hold tongs firmly. Open the kiln door, remove the ceramic tray (with your work on it), and close the door immediately.

•       Place the tray on a fireproof surface and allow your work to cool naturally. Do not hurry the cooling.

 

 

 

Q: How do I clean the exterior of my kiln?

Always ensure the kiln is completely cold and unplugged before cleaning. Wipe exterior surfaces with a slightly damp, soft cloth. Never use detergents, alcohol, solvents, or abrasive cleaners.

 

Q: How do I clean the inside (firing chamber)?

Unplug the kiln and allow it to cool completely to room temperature. Use a soft, lint-free brush to sweep out loose debris. If there is any dried contamination (e.g., enamel, clay residue), carefully scrape it off with a knife, then vacuum the residue. Be gentle — do not scratch or apply force to the ceramic surfaces.

 

Q: What materials should I never fire in my kiln?

The following materials must never come into direct contact with the kiln floor or ceramic walls:

•       Water, oils, or solvents

•       Silica or silica-containing substances

•       Alumina hydrate

•       Enamel powders, glazes, or glass (place on a ceramic support)

•       Fibre boards or blankets thicker than 1 cm

•       Any material whose behaviour at high temperatures is unknown

 

Q: How do I check the thermocouple?

Open the kiln door when the kiln is cold. Look at the back wall of the firing chamber — you will see a small metal rod protruding from the wall. This is the thermocouple. Check that its tip extends approximately 1 cm into the firing chamber. If it has been pushed back into the wall, gently reposition it. A recessed thermocouple will cause the controller to think the kiln is cold and may result in overheating.

 

Q: I have an optional view glass. What should I know?

Do not exceed 900°C when your kiln is fitted with an optional view glass — higher temperatures will permanently damage the glass. Always wear protective eyewear when looking into the kiln, whether directly or through the view glass.

 

 

 

Q: What protective equipment do I need?

At minimum, always use:

•       Heat-resistant work gloves when loading or unloading.

•       Protective safety glasses whenever you look into the kiln or are near the open door.

Keep unsupervised children out of your work area. Do not keep food or drink in your workspace.

 

Q: Is the smoke and smell during the first firing normal?

Yes. During the first few firings, you may notice fumes or an odour similar to burning paper. This is completely harmless and comes from cellulose-type bonding materials in the kiln’s thermal insulation burning off. Ensure good ventilation and keep anyone with respiratory health conditions out of the room until the smell has completely dissipated. This odour will not recur after the first few firings.

 

Q: Do I need to stay near the kiln while it is firing?

Do not leave a firing kiln completely unattended. If you need to take a break, turn the kiln to OFF (or to DISPLAY mode on Pro1/Pro1T to monitor temperature only). When your session is complete, turn the kiln to OFF, unplug it, and allow it to cool completely with the door closed.

 

Q: Can I leave the door open to cool the kiln faster?

No. Leaving the kiln door open — even partially — is not recommended. It can damage the ceramic chamber and door surfaces, and cause discoloration or burning of the painted surfaces near the door opening. Always cool the kiln with the door fully closed.

 

 

 

 

PART 2 — TROUBLESHOOTING GUIDE

 

This section covers the most common issues encountered with Prometheus kilns and their solutions. For issues not covered here, please contact Prometheus customer support at www.prometheushobby.com.

 

 

 

Cause / Solution: Check that the kiln is firmly plugged into a working wall outlet. Test the outlet with another device. Ensure the switch is in the HEATER (or ON) position, not DISPLAY or OFF. Check the power cord for visible damage. If the kiln still does not respond, a heating element or relay may have failed — contact Prometheus customer support.

 

Cause / Solution: Voltage drop is the most common cause. If you are using an extension cord, switch to a direct wall outlet, or replace the cord with one that is shorter and thicker (maximum 5 m; minimum 3 × 0.75 mm² for Pro1 series, minimum 3 × 1.5 mm² for Pro7 series). Voltage at the outlet may be lower than nominal — consult an electrician if this persists. The heating element may also be aging or partially failed; contact customer support if the problem continues.

 

 

 

Cause / Solution: First, check for a voltage drop (see T1 above). Also check the thermocouple position — when cold, open the door and confirm the thermocouple tip extends about 1 cm into the firing chamber. If it has retracted into the wall, reposition it. Finally, verify the kiln door closes fully and seals tightly.

 

Cause / Solution: The thermocouple may have been pushed back into the wall. If the tip is not inside the firing chamber, the controller will think the kiln is cold and keep heating regardless of the set temperature. Check the thermocouple position when cold and reposition if necessary. If overheating continues with a correctly positioned thermocouple, a relay may have failed in the “always on” position — contact customer support.

 

Cause / Solution: The thermocouple may be aged or slightly out of calibration. Use the Thermocouple Offset feature (tCOS) to make a fine correction. From the “Strt” prompt, press INCREASE to access tCOS. A positive offset increases the displayed temperature (which effectively lowers the actual firing temperature); a negative offset decreases the displayed temperature (raising the firing temperature). The maximum adjustment is ±11°C.

 

 

 

Cause / Solution: Check that the kiln is powered and the switch is not in the OFF position. On Pro1 and Pro1T, turn the switch to DISPLAY to activate the temperature readout.

 

Cause / Solution: This is completely normal. “VEr 1” indicates the controller software version and appears for approximately 2 seconds each time the controller is powered on.

 

Cause / Solution: This is completely normal. The programmable controller regulates temperature by rapidly switching the heating element relays on and off. The clicking noise is the sound of these relays operating.

 

 

 

These alarm codes are displayed if the controller detects a problem during firing. The firing is paused or terminated when an alarm occurs.

 

Cause / Solution: The thermocouple sensor is no longer detected, or the kiln temperature is more than 100°C above the controller set point. Check the physical position of the thermocouple probe inside the firing chamber — it must extend approximately 1 cm into the chamber. Check the thermocouple wiring connections. If the probe is damaged or broken, it will need replacement. Contact Prometheus customer support.

 

Cause / Solution: The kiln temperature is not rising as expected. This alarm appears when: (1) the heating rate is below 5°C per hour, (2) the actual temperature lags more than 56°C behind the target, or (3) the temperature is below 260°C. The most likely cause is a broken or failing heating element or relay. Also check that the thermocouple is properly positioned in the firing chamber — a mispositioned probe can prevent the controller from detecting temperature changes. Contact customer support if the element needs replacement.

 

Cause / Solution: The kiln has exceeded the upper temperature safety limit. The firing is automatically terminated. Let the kiln cool completely before the next firing. Review your program to ensure all temperatures are within the kiln’s rated maximum (1000°C for Pro1PRG; 1100°C for Pro7PRG and Pro7PRG-BD). If this alarm appears with correct settings, contact customer support.

 

Cause / Solution: The controller electronics are overheating (above 80°C). Do not attempt to clear this alarm until the controller has cooled naturally. Check that there is adequate ventilation around the kiln and that heat is not escaping from the kiln body toward the controller area. If the alarm occurs frequently, contact customer support to inspect the kiln for heat leaks.

 

Cause / Solution: The firing program is invalid — no Rate (rA) value has been entered, or it was set to zero on the first step. Return to IdLE mode and re-enter your firing program, making sure the first step (rA1) has a value greater than zero.

 

Cause / Solution: The Threshold Alarm temperature you set has been reached. This is a notification only — the kiln continues firing normally. Press any button to silence the buzzer.

 

 

 

Metal Clay

 

Cause / Solution: The temperature was too low, or the hold time was too short. Always follow the sintering specifications provided by your metal clay manufacturer — recommended temperatures and hold times vary significantly between brands and clay types. Also verify that the thermocouple is correctly positioned (see T2 above). For thicker pieces, a longer hold time is typically needed.

 

Cause / Solution: The firing temperature may have been too high, or the heating rate too fast. For thick or complex pieces, use a slower ramp-up rate to allow even heating throughout. Ensure the piece is supported on a ceramic shelf rather than placed directly on the kiln floor.

 

 

Enamelling

 

Cause / Solution: Temperature was too high or hold time too long. Reduce both and re-fire a test piece. Also ensure enamel did not come into direct contact with the kiln floor — always use a ceramic tray or mesh support. Any oils or residue on the metal surface before enamelling can also cause bubbling; degrease thoroughly before applying enamel.

 

Cause / Solution: Temperature was too low or hold time too short. Increase firing temperature slightly and/or extend the hold time. Re-fire the piece and observe.

 

 

Glass Annealing (including Bead Door use on Pro7PRG-BD)

 

Cause / Solution: Thermal shock is the most common cause of bead cracking. If using the bead door, the kiln must be pre-heated to the correct annealing temperature before inserting beads. Ensure the cooling rate in your program is sufficiently slow — glass must be cooled gradually inside the kiln. Do not remove beads from the kiln until the full annealing and cooling cycle is complete.

 

Cause / Solution: Confirm the kiln is at the correct annealing temperature before using the bead door. Keep the bead door closed at all times except when inserting new beads, to maintain the annealing temperature inside the chamber. Use a programmable firing schedule that includes a proper annealing hold and a slow controlled cool-down.

 

 

 

Cause / Solution: This is completely normal and does not affect kiln performance or safety. The ceramic components expand and contract with every heating and cooling cycle, and small surface cracks will inevitably develop over time. They are not a cause for concern.

 

Cause / Solution: This is a normal cosmetic effect caused by heat escaping when the door is opened. It does not indicate a problem with kiln performance. To minimise discolouration: avoid opening the door above 780°C, close the door promptly and firmly after loading or unloading, and ensure it is fully sealed whenever the kiln is firing.