I have got myself a second hand cromartie top loader to fuse glass. I know that purpose built glass kilns with digital controllers are more ideal but money won't permit the ideal. So, not knowing too much about kilns I am not sure how to set a ramp for my firing as the only dials my controller has is a temperature one - up to 1200 degrees c and what looks like a timer one from 0 to 90 mins, a hold switch and a cut out switch. I have looked at firing schedules and they say to ramp up to 600 degrees c at 200 degrees c per hour. How would you suggest I do this? I am willing to do a lot of experimenting but have not got a clue where to start. Does anyone know how quickly these kilns heat up? Can anyone tell me how my kiln knows that it has reached its set temp?
Sorry if I sound like I shouldn't be anywhere near an oven let alone a kiln, I am however a fast learner and did do a pottery/sculpture degree but had very little to do with firing the kilns and it was so long a go I can't remember much anyway. Thanks in advance, appreciate any help just want to get started.
Hi peego, do you have a picture of the controllee so we know what we are dealing with. Is there a temperature gauge attached to the kiln so you can see how hot it is? If not you may need to invest in a pyrometer.
If it is solely cone fired then you could save some money by converting the fusing temp into the matching cones and buying them, it will take some experimentation but its doable.
I have a ceramic kiln but luckily it has a basic digital controller so I just have to be there to reprogramme every segment
Righty oh! I know exactly how to do this ;D
The controller - does it have a tiny little screw to turn the temperature up? If so adjust the temperature to the highest you want to go - say 520 degrees. This is displayed digitally. Set the kiln to soak (hold) don't worry about the timing of this at this point.
The on the back of the kiln is a rotary dial - marked something like 1, 2, 3, 4, 5..
Starting at one - start the kiln firing - leaving the bungs out.
Keep an eye on how the temperature on the readout is going - this way you will be able to 'manually gauge' the speed of your ramp.
If the ramp (or raising temperature is too slow then turn a dial up a little more to fast then turn it down)
Keep a eye on it - the temperature increase will be a bit slow at first as the kiln lining will absorb some of the heat, as it gets going it will speed up a bit. Eventually it will slow down considerably.
Continue adjusting the rotary dial upwards (turning the temperature up) to keep the kiln firing to schedule.
When you have got the to 'first set point' (first ramp stage temperature) you can put the bungs in and turn the dial to full power.
When you are getting near to the desired temperature you should keep nearby
As the kiln switches of open the bungs to quickly drop the temperature (but don't go below 500).
Then put the bungs back in and leave it alone until it has fully cooled down.
These ceramics kilns are extremely well insulated and cool down quite slowly (compared to bead kilns) and annealling will occur during the cooling period withou any extra 'controlling' of the kiln.
I don't know how big you can go with you glass pieces as I have only ever done small bits such as cabs and pendants, though I did think about doing some coasters but never got around to it.
I made some notes and this is the schedule I found somewhere:
First ramp (set point 500 C) 4-5 degree inc per min.
The rapid heat to the desired temperature and soak (hold the temperature) for 5 to 15 mins.
Then crash - take the bungs out to drop the temperature - remember don't go below 500 C.
Bungs back in an leave it alone.
If you google Cromartie HobbyTec you will be able to find an instruction manual onlin that you can download. Same for the controller. If you have any problems I may be able to email you a copy of mine (assuming it's the same controller model)
I haven't done any fusing for a few years - I use my kiln to anneal my lampwork beads and for some ceramic firing (though there hasn't been a lot of that going on for far too long either). ;D
Terri you are an utter genius and I am in awe :-*
What a comprehensive answer, that should set you fusing Peego :)
Tan, I wish I was a genius ;D
But it is just experience. I've been using kilns for more than going on 25 years now - mostly for ceramics.
Forgot to say. After the soak - switch the power off. Either press the button for the hold/cut off to - cut off, or reset the dial to 0. (unless of course you can set the soak time on the controller).
hi
I am so greatful for the time people have taken to help me. Unfortunately it isn't a digital controller and I don't have any dial with numbers on that I can use to set a ramp. I only have 2 dials, one that says 10 to 90 which I am assuming is a timer and the other which is a temp dial. i am trying to add a photo. Don't give up on me yet!
Thanks
Hi am back with my original problem and photo.
Hope this link works and i have done it correctly!
http://www.flickr.com/photos/80214644@N02/7353786014/in/photostream
Thanks
Peego I'm sorry, that is a controller I have never seen before, I'm wondering if it should be attached to the kiln in some way?
The dial on the left is the power - like the rotary controller I mentioned that would be on the back of the kiln. The other is the temperature.
So set the temperature by turning the dial. The start the firing off and gradually turn the dial on the left up to increase the power (heat input) up. Leave the switch set to 'hold' and when you are ready to switch off flick it to 'cut off'.
The controller should be connected to the kiln via a plug into the kiln or hard wired in. Which kiln model do you have?
If you are having any problems connecting it all up then contact Cromartie Kilns - http://www.cromartie.co.uk - they are really helpful. I emailed them with an enquiry and they rang me back and talk me through the entrie process that I needed to do to re-wire mine.
edited to add - BTW you can get fully progammable controllers for some of the older Cromartie kilns, but they are quite expensive. Again have a chat to them and they will advise you if you can put one on and how.
Ahh I get it now, so the 123 is actually 100 200 300 c? And the dial on the left is similar to low med and high?
hi
Thanks so much again. The controller is attached to the kiln via a thick cable wired into the back. It is just fixed onto a little board as I expect the previous owner had it wall mounted for ease.
So my little book with firing schedules tells me to get to a temp of 677 dgrees c at a rate of 222 dgrees c an hour. Would you suggest I set the temp dial (one on the right) to 677 and then put the other one to about 20 perhaps and see what happens? Do you think one of the lights in the photo will go out when it has reached temp or is that a bit advanced for my controller and kiln, am I expecting a bit too much. do I just put it on hold and hope for the best? Can see myself experimenting experimenting experimenting for days to come!
Thanks
Quote from: Peego on June 09, 2012, 11:06:43 AM
Can see myself experimenting experimenting experimenting for days to come!
Thanks
Even with a digitally controlled glass kiln, you find yourself doing that!
I'm sure Terri will be able to advise better, but I'd go with 20 personally for the rate, little harm can come from going slower rather than faster - the biggest downside to slower firing means you're risking being in the devitrification zone for longer, but heating too fast can mean thermal shock, so, especially whilst you're experimenting, its the lesser of two evils!
Best advice I can give, is start with scraps and small pieces. I know when you get a shiny new kiln (or old one) the temptation is to take that firing schedule, and a couple of large sheets of brand spanking new Bullseye and fire it all straight away - don't want to be firing the kiln with hardly anything in it, waste of electricity, right? Personally, I'd rather waste a quid a or two of electricity and scraps, than £20-£30 worth of art glass.
I'd been fusing for 18 months when I got my first kiln, but I *still* only did small pieces for the first several firings, even though I'd successfully fired larger pieces at college - I didn't start firing the larger pieces until I felt I'd got to know my kiln and the best schedule for it.
Have fun, enjoy the experimenting, get ready for some surprises when you open it, and don't forget to show us photos!
thanks very much Dawn. will get to it this afternoon. Have got loads of scraps so will be testing those for sure.
Will let you know how I get on!
fingers crossed.
I have a hobby tech 45 which originally had a kiln sitter that I used for several year for glass until I needed to cast and control the anneal a little better. Sounds like you won't need them but I do have minibars for the sitters for fusing and slumping temps if anyone would like them.
The relay light will probably come on whilst the power is 'on' ie you will hear the kiln clicking between 'on' and 'off' - a bit like the thermostat in an oven.
I guess the other light will be on permanently whilst the kiln/controller is connect to the power source.
So yes, set the temperature dial to the temperature you want to go to and start turning the other dial up a little at the time. I would probably start at 10 or 20.
The biggest operational problem I think you will have is judging the temperature you are at, therefore, it will be difficult to judge if the 'ramp' is progressing to fast or too slowly.
You can buy handheld thermocouples that have a probe that goes into the kiln and will give a digital readout, one of these will be a tremendous help. These are often called pyrometers.
Alternatively you could try using Orton Cones. These are little sticks of a special clay that are designed to wilt at certain predetermined temperatures (a fairly loose description). The temperature they wilt at depends on how fast the temperature is climbing. See this link http://www.greenbarn.com/PDFs/Orton_Cone_Chart.pdf
I would suggest that the cones 019 - 022 would be best for you. Always use a range of cones - 022 will wilt before 021, then 021 will wilt before 022 etc - so you can see that you are getting near to the temperature you want. You set them on a kiln shelf just inside the bung hole and need to peer through the hole to see what's happening. (H&S says you should wear some kiln googles to do this.....I've never bothered, but....). You can get cones from any decent pottery material supplier. As you can see from the chart on the right of the link the cone numbered 019 will wilt at 695 degrees if the ramp is 15 degree per hour, 678 if it's 60 degrees per hour and 695 if it's 150 degrees per hour. You can get self supporting ones or the standard ones which need supporting with a little sausage of clay wrapped around them. You will need to stand them on some kiln paper or a bit of kiln shelf that has been coated with kiln wash or bead release, or they will stick to the shelf.
Other than that you could try contacting Cromartie kilns to see if they have a second hand digital readout controller that suits your kiln.
Yes you will need to experiment.
Thanks Teri, you have been a tremendous help. am just going to have some lunch and then nervoulsy will begin. watch this space! Will let you know what happens.
Thanks
Lots of luck Peego, I am really interested to see how you get on and am jumping around in excitement, its like waiting for a baby ;D
Quote from: Flyingcheesetoastie on June 09, 2012, 12:37:23 PM
I have a hobby tech 45 which originally had a kiln sitter that I used for several year for glass until I needed to cast and control the anneal a little better. Sounds like you won't need them but I do have minibars for the sitters for fusing and slumping temps if anyone would like them.
Rachel, I have a kiln sitter and would love to take you up on your kind offer, can I cover postage?
Peego, get yourself a small notebook ( say 4x7 inches) and start with page 1. List the settings you are using for the firing, temperature etc and a short description of the pieces you are firing and type of glass.
At the end of the session, write down whether the results were good or not what you wanted and list reasons. I know it seems a big pfaff around but after a few firings, with each one being on a different page, you can refer to the page when you want to do a similar firing. That way, you'll create a fantastic resource for yourself so that each firing you do will be successfull. If you put in the start time too, you'll be able to judge when you want to vary the hold periods if you are using a sequence of firing temperatures. It means you won't have to sit by the kiln but will know when to adjust any setting. Useful for me when using my big old Fulham pottery kiln as it lives in the garage.
Thanks everyone, coming to the end of the firing! Can't wait until it cools down and I see my results. Not bothered whatever happens as I feel I have now learnt a lot about my kiln from the very first firing. Been into that garage every 10 mins checking temperature and noting everything down. Have been so excited. Will post my results tomorrow. Will also probably have a whole new set of questions too!
Peego you are absolutely going about it the right way, and it reads like you are having a blast and if you enjoy it through this difficult learning bit then you will sail through the rest of it.
Pat's advice about a notebook is invaluable, I made all sorts of notes on my initial firings and it is those schedules that I now use time and time again.
Tan - I'll look out what I have left and drop you a line!
Thanks flower ;D
Peego, how did you get on?
Hi
I am so amazed everything worked perfectly! Thank to you everyone for giving me the confidence to just go for it. I did only throw some scraps in to practise with but everything has fused together exactly how I thought it would be. I finally emptied the kiln about midnight last night after seeing some friends, I just wanted to get home though and see what my results had been! Am delighted and can't wait to have another go, using what i have now learnt. Hopefully I may now be able to refine it a little so that I don't have to monitor what the kiln is doing every 10 mins! This obviously helped me understand what my kiln was doing so all valuable.
Thanks again. Will post pics of the real stuff I make after a couple more test firings.
Thanks again.
;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D
Well done Peego and nice one Terri ;)