Kiln Diary.

I bought a kiln, second hand, off eBay, and I wasn’t actually too sure how to use it.  
Along the way I’m still struggling to find all the answers to my questions. So I’m keeping notes of what I am discovering. The result is I am realising it isn’t as scary or as difficult as I had convinced myself.
This diary is a log of me learning to use my kiln. My way may not be the best or the quickest so don’t take it as the right way. But I hope what I’m finding out and the resources I have come across may be useful to someone.

Kiln update. November 2012.

I have been using my kiln quite a bit recently. All the problems seem to have been fixed and I'm really enjoying the work I'm doing. I still get worried things are going to go wrong and sometimes my kiln hasn't started straight away like it should ( there should always be a burst of power as soon as I press start) but it has always been down to not closing the lid properly or the kiln being on uneven ground (my garage floor is very bad and it is a slight hill). The kiln isn't too bothered about a slight slope but it does pick up if it is very wonky. I've bisqued and glazed work now and I've monitored the temperatures with orton cones and the kiln is behaving very well. 

Trying to fix the kiln has been very stressful and very upsetting. But even though it has taken a lot of extra money it does feel worth it now. As a first time user of a kiln trying to solve all these problems has meant I know a lot more about kilns than if I'd bought a new perfect one.

New controller. Aug 2012.

I looked into the Stafford Instruments controllers as they are made in the UK. The controller that came with my kiln is from Germany which would mean it'd very expensive to get fixed or maybe replaced. 

The Stafford website is really helpful and there is a lot of complicated information but it is well supported with explanations. There are lots of controllers and each controller can be adapted depending on how you want attach it to your kiln. So you can hardwire them in, you can plug your kiln's power plug into the controller or you can plug the controller itself into a socket certain kilns have (my cromartie doesn't have one of these sockets). I am still very confused about these different fixtures but Stafford are so good I don't need to understand it.

There was a few different controllers I considered but the one I've now got for my Cromartie Hobbytech is the Stafford Instrument ST315A. It is a lot more complex than my original controller having 9 program's with up to 9 segments per program. It not only has heating ramps but can also control the cooling too. It is quite different from the old controller in that the information it needs for the firings is slightly different. Here is how I've changed my bisque fire to suit this controller:

Segment 1:
Ramp degrees/ hour, 60
Soak temp, 600
Soak time, 0

Segment 2:
Ramp degrees/ hour, FULL 
Soak temp, 1120
Soak time, 0

I didn't install the controller myself but my dad hard wired it into my kiln for me. The one bit of information this controller needs is the themocouple type of the kiln. For a Cromartie Hobbytech 45 the thermocouple type is 'S'. Kilns will either have a R, S, K, or N type thermocouple. I need to find out what these actually mean...

Mega stressed. Aug 2012.

I am pretty upset to say that the thermocouple replacement hasn't made things any better. The kiln was behaving the day I wired the thermocouple out which made us think it was that. It also almost made it through the test fire with the new part: 1 hour to 300 degrees then full power to 1000 degrees. It made it to 800 degrees (much better than it had ever done before on any firing programme) and then started blacking out and the controller switching itself on and off again. It was going so well I thought it was sorted!
I am exploring two avenues now: getting a new kiln or I've sent an email to Stafford Instruments about my options for getting a new controller.
If you have any advice on what you think I should do then the support would be really appreciated.
Thank you,
Jessica Adams.

Hi Jessica,
I did say originally that I suspected the controller. We also supply replacement controllers the page is .
It could of course be a lose wire causing the erratic behaviour.
Let me know how you get on.

Thermocouple. July 2012.

The thermocouple sits in the back of the kiln and feeds through into the chamber. It is the little nubbin I can see on the inside that reads the kiln temperature and communicates with the controller. My current thermocouple is in pieces and the two wires inside are touching and it has actually dropped off now the back off the kiln is open. It could be the cause of the kiln blacking out as it may be confusing the controller.

I ring Cromartie man. He suggests I try a little bit of re-wiring just to confirm it is the thermocouple that has been causing the problems. What I do is wire the kiln up as a complete circuit but minus the thermocouple. The kiln will work but just won't know what temperature it is inside the chamber. I’m going to do a test fire (to 1000°c pretty fast) in this configuration. The controller will display the ambient temperature inside the kiln throughout the firing. So it will be stuck on around 18°c without the thermocouples information. If it is the thermocouple that is at fault then without it wired in the kiln should perform successfully and the power should be fed through without blacking out.

I test it for 20 minutes before switching the kiln off. The power goes through in short bursts for the ramp no problem. It doesn’t black out. It appears to be working.

I ring Cromartie technical team back and am put through to sales to order a replacement thermocouple for £65. It is good that all these parts for an older kiln can be so easily purchased. 

Time to sort this out: communication with Cromartie technical team... they are good. July 2012.

I have a Cromartie Hobbytech 45 with H3i controller and it is 11 years old. The kiln is in my garage plugged directly into a 13amp ring main socket by itself. I am encountering a fault every time I fire but I don't know what the problem is.
The kiln has completed a test, bisque and glaze firing and by using orton cones the kiln is reaching the right temperature and the ware is coming out good. But it takes a few try’s to get going every time. The kiln appears to be 'blacking out' during the ramp and not recovering. The controller is able to read the kiln cooling down but can't feed any power to the kiln without failing.
It seems that when the controller try's to feed power to the kiln both the controller and the kiln are blacking out.
I have cancelled these programmes and started them again and it repeats this problem until a few goes later it fires successfully. It has fired on the second try but also on one occasion it has taken 5 goes to complete the ramp. It always completes a programme if the kiln gets through the ramp period.
I would be very grateful for any tips or help!
Thank you, Jess Adams.

Hi Jess,
It sounds like the controller is a bit faulty.
The costs of sending it back to the German manufacturer for evaluation would I think be prohibitive and so if you can make it work by re-setting I would be inclined to do that until it fails completely. Also check that the Thermocouple wiring is ok just in case there is a momentary disconnection.
If the controller fails completely it can be replaced with an updated model, British made.
Hope this is of some help.

Thank you for your help before, I've kept our previous emails attached for reference.
The time has come where the kiln has now completely failed. When the firing programme starts the power is being fed through to the kiln for the first few 'bursts', but is now blacking out around 30 degrees and refusing to continue at all even when I cancel and start again and again.
As I've come to terms with the fact I may have to buy a new controller/ or even kiln we're having a  thorough look in the back of the kiln. We have noticed the thermocouple is cracked in three places and without putting any force upon it the wire has given way and the thermocouple has now dropped off. Could this be the problem?!
Jessica Adams

CROMARTIE: left a voicemail message on my phone to ring them.

Another Bisque. June 2012.

Same program as before. Same range of clays. 

But the kiln is really playing up and I’m beginning to become very stressed and unmotivated because the kiln is so untrustworthy. And each time I use the kiln I just don’t know what to expect. I’ll try best to explain the problem that I have experienced every time I have used the kiln:

The kiln will start the firing programme. During the ramp the power will be fed through in short bursts to control the temperature build. Therefore the green light that indicates power to the kiln will be buzzing on and off. It is obvious when power is being fed to the kiln as the green light will come on on the side of the kiln and there is this buzzing noise. Once the kiln has completed this ramp it switches to full power where the light and noise remain constant until the program is complete. The H3i controller hardwired into my kiln has lights that display the temperature in the kiln and what segment the program is at throughout the firing. 

The problem that keeps happening (and it is occurring anywhere in a firing, ramp and full power) is that when power is being fed into the kiln the controller ‘blacks out’, all the lights turn off the display and flash on and off, the controller clicks loudly when trying to get power going again, the green light on the kiln flashes on and off when the controller does. The power cannot be fed to the kiln and it does not recover and the program has to be cancelled. Rubbish.
I am really regretting buying a second hand kiln especially off eBay as it was obviously faulty when sold to me. Also if I had tested the kiln when I had first bought it I would have been able to get my money back. My advice: BUY NEW, TEST STRAIGHT AWAY!

Glaze prep, application and firing . May 2012.

I have two glazes that can be applied to all three types of earthenware clay. I have bought Potterycrafts brush on earthenware glaze in white and transparent. They come in 472ml pots (bottles about 15cm tall) and are around £10 depending on colour. I did wonder if there would be a brush attached to the inside of the lid, but there isn’t so I had to buy some brushes which was good as I got a range. All the materials I have bought I’ve got through the same suppliers, Bath Potters.

As the glazes have been frozen and just because they’ve been sat around for a while I sieved them both through a 100 mesh plastic test sieve. It was a bit too much for the test sieve and it wore away pretty fast so something a bit more heavy duty would definitely be worth the extra cost in the long term.

I also bought some glaze pencils. I have black, red and yellow. They all have different temperature ranges which will be shown on the supplier’s website. Some colours will burn out at much cooler temperatures than others. With the glaze pencils it’s advised to sharpen with a craft knife so I did. I cleaned the bisqueware and drew on it like I was using a normal pencil. Really satisfying! 

Now it is time to apply the glazes! I’ve made sure all bisqueware is dirt and dust free by wiping it down and the glaze pencil pieces were prepared earlier. For the pieces with the glaze pencil on I’ve sponged on the first layer of glaze so not to smudge the pencil, allowed the layer to dry and then painted on the next layer. For all other pieces I’ve applied all layers with a glaze brush. Always waiting for previous layers to dry. I have applied two to three layers of glaze to each piece. I haven't been particularly neat in application with pieces towards the end.

The temperature range for both these glazes is 1015-1060 °c. For the first glaze firing I’m putting all clays in together and firing to 1040°c. Here is my program:

    1.       Delay, 0 minutes
2.       Ramp, 6 hours
3.       Temp1, 600°c
4.       Temp2, 1040°c
5.       Soak, 10 minutes

The kiln misbehaved as usual for this firing and it took a few goes restarting it before it completed a program. The work came out well, again showing how resilient these materials are to heat and impatient preparation! Need to sort the kiln out though. Definitely faulty.

Bisque Fire. March 2012.
All three clays can be fired to 1120 degrees. So for the first bisque I'm going to try all clays together. Pictures of the small samples I'm firing can be seen on the main page of my blog. Here is my firing programme:
1.       Delay, 0 minutes
2.       Ramp, 10 hours
3.       Temp1, 600°c
4.       Temp2, 1120°c
5.       Soak, 0 minutes
The firing has been successful and all of my samples have come out in one piece. The kiln took two trys to get going. Initially it heated up to 300°c and then all power shut off to the kiln, which is similar to the problems I had before. But the kiln was on level ground and the lid was properly shut so why this has happened I really don't know. I cancelled the firing and started it again and then it worked fine. The kiln did take the 10 hours I programmed to reach 600°c, and then only took 2 hours to reach the top temperature of 1120°c. I started the second firing at 8pm and left it overnight, woke up at 5am just before it hit 600°c, checked again around 8am and the programme was complete.

Clay Prep. March 2012.
I have finally found the time to prepare my clay. I've bought a slab of stone as a work surface and some heavy duty plastic gravel bags to store the worked clay. The three clays I'm prepping are: Potclays studio white earthenware, Scarva black earthenware and Potclays semi porcelain earthenware. All of these clays are new to me and I'm not sure how they are meant to feel, but after unwrapping them for the first time I am positive the freezing and thawing has left all three a bit too wet. There are also thin cracks running through the surface of the clays. For the prep I'm following the instructions in Peter Cosentino's 'Creative Pottery'.
"Kneading: roll the clay into the shape of a swiss roll and turn the roll to face you lengthways on. Take hold of the end furthest from you, and pull it back towards you, folding the clay over. Press firmly down away from your body... repeat the whole process several times until you find that the clay has grown too long to handle... turn the clay so that you are facing it lengthways on again... continue..."
"Wedging: take a piece of clay and raise it to head height, and then slam it down forcefully on to the wedging surface. Lift the clay off the slab, turn it 90 degress and slam it down on the surface again... rotate it again... you should now have a four sided block... slice the clay into two or three sections and slap the pieces together hard, to prevent air being trapped between them. Repeat the wedging process. Cut through block with wire and check the inside surfaces for any air pockets."
Small lumps of each of the three clays have been kneaded and wedged and any air pockets have been removed. The clays now feel less wet and more plastic which I guess is good sign. Ready for making!

Uh-Oh, Everything Has Frozen. February 2012.
I have recently bought my materials, I have bought all my clay and glazes through Bath Potters Supplies. However the weather has been pretty chilly and as a result all my new materials have frozen. All my bags of clay and glaze have turned to blocks of ice. I've thawed them out and they are nice and squidgey again. I've been trying to comfort myself with the fact clay is from the ground and the ground freezes all the time in winter... The information I've found online has been mixed. Some people think frozen materials are ruined as the different molecules that are bonded will have separated... or whatever. But the advice I am choosing to take is that it will all be fine if I carry out a few procedures. The clay will need to be re-wedged, big time, but it should survive. The glaze will need to be re-mixed and re-sieved and that should survive too. I will be doing this soon so watch this space. Fingers crossed.

NOTE AUG 2012- After thawing and reworking the clays and sieving the glaze through a 100 mesh sieve I am 98% sure the clays are fine and 85% sure the glaze is too. More testing definitely happening once all kiln problems are sorted!

Test Fire Take Two. November 2011.

After all the worrying and thinking I was going to burn my house down, half a year after buying the kiln I am doing a test fire. I need to know if my kiln actually works. So out comes the furniture, 2 inch props in the bottom then a shelf, 4 inch props in the middle then another shelf and the 1 inch props scattered on top for good luck. Lid down!
The H3i controller has a test fire programmed in as P=9. The programme is separated into five sections.
1.       Delay, you can programme the firing to start now or in 5 minutes, 2 hours or whatever
2.       Ramp, you programme how long you want the kiln to take to hit ‘Temp1’
3.       Temp1, the temperature at which the kiln turns to full power
4.       Temp2, the top temperature of the firing
5.       Soak, the duration of how long you want the kiln to hold ‘Temp2’

I am doing the test firing described in my instruction manual, it is:
1.       Delay, 0 minutes
2.       Ramp, 1 hour
3.       Temp1, 300°c
4.       Temp2, 1000°c
5.       Soak, 20 minutes
I am not actually sure how long this will take to complete.
I hit start for P=9. On the controller the ramp light is on and the display is showing the ambient temperature inside the kiln of 13-14°c. I wait for the temperature to rise, still waiting 20 minutes later and nothing has changed. The kiln is programmed to reach 300°c in the first hour so I know something is wrong.
I then notice the light on the actual kiln is not on. When the green light at the back of the kiln is illuminated it shows that power is being fed to it. It hasn’t turned on once but there are no error messages on the controller, it still shows the temperature. So I accept that it isn’t working and have to figure out how to cancel the firing. Turning the kiln on and off at the wall will not work as it will automatically return to the firing programme it was doing. So I consult the manual for the H3i controller this is what it says:
“Once a program has been started, it must be completed. If the ‘Start/Stop’ button is pressed during the firing it will go into PAUSE mode which is indicated by all the LEDs on the front panel of the controller flashing. Then to stop the program all the program values currently stored must be reset to zero. Press the ‘Start/Stop’ button and the LED will go to end. If the power is then switched OFF & ON the program that was being fired will have stopped and the original program details will be displayed.”
So I did this and it worked. It’s probably good that I learnt this early on.
I really have no idea what is wrong. I can find no help online. I fear the worst: I have bought a kiln that does not work. It is suggested that I call a technician at the Cromartie headquarters but I am not keen as my cover will be blown and everyone will realise I don’t know very much about kilns.
I sit around for a while and then realise I’ve just got to call the technician. I find the number through the Cromartie website and call it. The technician is really nice, isn’t patronising me and I surprise myself with technical talk. It is suggested that I check the ‘interlock switch’ which I have never heard of but the technician tells me it is a fixture on the lid which secures it down shut, turns out my kiln doesn’t have one (but never was meant to have one). The technician tells me it sounds like I’m having one of the two most common problems, either the kiln isn’t on even ground or I haven’t shut the lid properly. So I unpack the kiln, reposition it and get the spirit level out. Even though all wheels are on flat stable ground it turns out my garage is actually on a slant and the bubble is way off. So we prop up the front wheels with a ceramic tile and the spirit level now shows it to be even. I re-pack and make sure the lid is shut properly this time, switch the kiln on, start P=9 and it works! The green light comes on and the kiln does make a low buzzing noise.
The kiln doesn’t hit 300°c in the first hour like it should. It only reaches 70°c in the first hour. The green power light was not on constantly either. We thought about cancelling and starting again but instead the kiln was given a bit of a wriggle and the light popped on and stayed on. However, the kiln now recognises it has been on for 1 hour and although it hadn’t reached Temp1 it flicks over to full power and within 15 minutes is 228°c. This is where I still think the kiln is going wrong, I will have to try a test fire again. My uneducated hope is because it hadn’t been used in ages it was simply warming up or the floor was not level again. I’m sure that the light should be on fully and not on and off.
From this point on the green light remains illuminated and the kiln is making a low noise. As the kiln gets hotter and hotter I can hear the fire bricks rustling and expanding.
By 3 ¼ hours the kiln is at 943°c and there is a red glow between the lid, it is very hot to touch but not much heat is being given off around the kiln which is good.
At 4 hours and 34 minutes the kiln hits Temp2 1000°c and the controllers ‘Soak’ LED comes on. The temperature fluctuates between 986°c and 1004°c for the 20 minutes.
After the 20 minute soak the light on the kiln goes off, the controllers display flashes END and also shows the temperature. In my instruction manual it says a kiln with ware inside should not be opened until under 100°c, I’m going to do this even with the test fire.
I began this firing at 13:45. It hit top temperature at 17:19. It ended the firing at 17:39. At 23:50 the temperature was still 220°c. I left it for the night (plug still on) and at 10:30 the following morning it was 30°c so I opened it up. I need to work out the cost and energy consumption which I’ll post at a later time.
Overall, I’m 85% sure it works. Hoorah!
Test Fire. September 2011.
I prepared myself for a test fire but there was one thing I really wasn’t sure about: do you test fire with the furniture in the kiln? I thought yes but could just find nowhere to confirm this assumption.
I found this video on YouTube, so I assumed yes you do put the shelves in. There are links to some other interesting videos from the Skutt kiln company too.
So I got my furniture out, it was still the two 14 ½ inch shelves and the three 6inch props that had come with the kiln. I then I wasn’t sure I actually had the correct amount of furniture. I worried. With the one shelf resting on the bottom (which I was unsure about) and then the next shelf on top of the 6 inch props the second shelf was actually resting and putting weight on the thermocouple. So I called it off and went to buy new furniture.
This is the company I used.
The products are really quite reasonably priced but I got caught out on the postage and packaging as my order doubled in cost. But to be fair the package was on my doorstep less than 12 hours later. My kiln furniture now consists of two shelves, three 6inch props, three 2inch props, three 4inch props and six 1inch props. But I wish I had bought some spare half kiln shelves now.

Positioning. September 2011.
According to my instruction manual the kiln should be on level ground which is made of a material that isn’t going to set on fire. Then to allow the air to flow around the kiln it should be set atleast 30cm away from any walls and there should be nothing above the kiln for 1m. Also the kiln has to be plugged in to a mains socket not an extension lead and it should not share the socket with any other appliances. So my kiln is in my garage on a concrete floor, it has the minimum 1m allowance for the air flow above as there are wall mounted cupboards and it is set over 30cm away from any walls . Boom.

Cleaning It Up. September 2011.
As the kiln is second hand there is some wear and tear. Some off the fire brick grooves around the elements have been damaged and bits have fallen away. Also there is loose fill from the bottom of the kiln that is now sitting in the grooves in contact with the elements. The brick that has cracked off is in quite small sections (20x30mm) but I’m unsure about whether to remove the pieces leave them in place or fix back in with kiln cement.
This website mega helped and I know I’ll use the advice again.
I removed all loose and broken brick carefully and then vacuumed the entire kiln with a soft brush attachment until all debris was removed. I’ve kept the bigger bits of brick just incase they will need to be fixed back in. I wiped down the kiln shelves and props so there was no dust on them either.

Collection. June 2011.
My Dad drove me to Reading in his saloon car to collect it. We took quilts, blankets, rope and bungee cords to try and keep the kiln stable and secure in transit. It was pretty lucky we took his bigger car because the one thing I wasn’t prepared for was how massive the kiln actually was. My expectations had been majorly biased by the photos on eBay and by thinking it was a small hobby kiln being only 45 litres internally. But I overlooked the outside features and controller which are massive, therefore, the weight of a kiln is a lot and lifting into a car can be troublesome. I couldn’t lift the kiln even with help so my Dad and the seller had to do it (he had just had a hip operation). We wrapped it up and tied it to the car body and off we went.

The Kiln. June 2011.
I had looked into buying a brand spanking new kiln. There are so many companies and different styles to go with and I am quite taken by the new ‘eco-friendly’ kilns that seem to be around. However, the price tag will leave quite a dent in your savings and I do love a bargain so therefore will opt to pay as little for something as possible. So I went to eBay.
I had a few pointers on my list. Firstly, it had to be an electric kiln, top loading, preferably small and have a clear digital controller rather than an autositter controller because to me they look incredibly fiddly. Also it had to be around £500-£600 (well over half the price of a new one). As for the actual kilns on auction there had to be lots of photos showing the kiln was in good condition, instruction manuals and the wiring diagram included. If furniture and other bits were included that was a huge bonus.
I watched many auctions, asked the odd question but never was brave enough to bid and was always disappointed when the bidding finished and I hadn’t got a kiln. Then a kiln came along that met most of my criteria although it didn’t have the best description. But after a bit of communication with the seller I realised it ticked every box and it hadn’t actually been used that much. I really got attached to it and found myself just looking at the eBay page every day trying to figure out what all the other bidders were doing. I decided to go for it. Within the final minutes the kiln price went over my budget and I was retiring to the fact it wasn’t mine. But through some tough talking from Paul I put in a big bid in the last few seconds and WON! I haven’t once regretted spending more money than I intended too. Just see now whether it works…
My kiln is a Cromartie Hobbytech 45 (litre) top loading kiln with a H3i temperature controller. The advised top temperature is 1260°c. The controller allows the kiln to do 8 different firing programmes and a test fire is also pre-programmed in. It also came with the original furniture: two shelves and 3 props. It looks like this
A lot of helpful information about Cromartie kilns can be found on their website. They also have an archive of instruction manuals for the majority of their kilns so if you’re buying second hand and the manual isn’t included it isn’t a disaster.

1 comment:

  1. Love your diary. Im in same boat with a new old kiln, no manual and a steep learning curve. My elements have gone so thats my project for this week!
    All the best