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sulamaye

Will Cromartie Kiln Fire To Stoneware?

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Hi,

 

My very old small top loader has finally given up on me and I am looking at buying a second hand replacement. I've been looking at a cromartie hobby tech 40 with a sitter, and the seller says it will fire to 1260 cone 7-8 I use, on 13amp plug, but I've seen someone else blog that working it out technically such a kiln will never reach stoneware.

 

Can anyone advise me whether this kiln will really reach stoneware regularly, it's all I fire to? Or whether the person is correct and it is a theoretical temperature of 1300 that is achievable but not what will happen in the real world. I don't want to buy a white elephant. Thanks

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I have a very old rusty one exactly like that or an even older model. Had to gut all the electrics except the elements as they didn't work and I only have full power or no power but gets cone 9-10 happily in 6-7 hours. Definitely worth it for the right price as you get space for 12ish mugs, size depending.

 

Found a picture of some pots and the cones from I think a 6.5 hour firing. Maybe 7. Cone 10 is most of the way there. 9 and 8 very flat.

 

1888982_254222654755296_1082444829_o.jpg

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Wow Joel - I'm amazed it reaches those temps so quickly. I have a Hobbytech 40 - old but in VGC and had elements replaced when I bought it 4 years ago. I can get it to 1200oC - it seemed to struggle at the top end but got there in the end - more like 10/11 hours!

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The elements in my kiln have a total resistance of 18 ohm so at 230-240 volts that gives me the 12-13 amps for the plug socket.

 

In theory it is VA for kw/h so 230 x 13 = 2.9-3.1 kw/h

 

Celia, I don't actually know the temperature the kiln gets to, never stuck a thermocouple in. All I have are the cones. I would like to go a little slower but the only switch for the kiln is at the plug socket. I would be interested to know the resistance on your elements and see if they match. Mine looked hardly used when I bought it.

I have only fired the kiln 4-5 times, nothing like the 4 years use so it could slow down. The biggest problem are the lids made out of fiber. Mine is so rusted but I think it sat out in the rain for a good while. I have seen many go through ebay with rusted lids so I think it has a few ventilation problems anyway.

 

Bought it for the idea to experiment with electric reduction but still haven't made it round to that yet :D For £67 I couldn't help myself. 

 

I am maybe a little hard on the kiln but it can definitely get 1260 or a good cone 9

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Sulamaye - I'm really a novice on this and can only say what mine does. There is a lot of heat loss when it gets near the top temp, so the elements are battling against this to achieve the final increase. If the seller has used it at stoneware temperatures it sounds as if it's in good enough shape. I understand that if used regularly at the high end, the elements don't last as long, so be prepared to pay out for replacements every so often. It would be a good idea to phone Cromartie kilns for some definitive answers. Or someone who does kiln maintenance even - they'll be sure to know this model, they are so common. If I was confident putting insulation around the outside, it would be something I'd consider to reduce heat loss, but I already get a bit nervous every time I fire it and would worry about 'wrapping it up'.

 

Joel - you've got me on that one - I don't know how to measure/calculate the resistance?

Mine is plugged in to a standard (UK) 13 amp socket. Because I was having a lot of trouble with glaze cracking which I thought was due to rapid cooling, my husband bought me a digital controller and I fired down for a few firings. I don't do that now, so I guess it was another reason!! Before that I was just using the sitter with minibars. There is a 0-1-2-3-FULL dial, which I used to use for a slow warm up, now of course I use the controller. I am at last going to start using cones so I will have a better idea of the heat work. Something else to get my head round!

Mine is in the garage and had some rust on the casing around the control box, then developed more around the bung opening on the top (some rust flecks fell into the kiln once and melted into the glaze on a nice white earthenware bowl!!!) I painted the rust areas with hammerite - brilliant!

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celia, you painted the rust on the KILN, not the bowl, right???  recently some black spots have appeared on (naturally, only the white ones) several pots.  cannot figure out what they can be but i have ordered some of L&L's brush on finish for the inside of the lid.  the spots only happen on the top shelf.

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If you own a multimeter it is quite simple. Unplug the kiln. Turn the dial to ohms, there will probably be a few different resolutions/scales. Put one of the probe things at the start of the first element where the power goes in and the other on the end of the last element where the power is leaving the elements. These kilns are just one long element really, or at least mine are wired up in series.

 

Like this picture but the resistor is your element wire.

 

range10k.jpg

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And it measures the resistance with no electricity going thru? Can u test whether the elements need replacing that way? Is it putting a charge thru and measuring the resistance is that what it does Joel?

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Not sure how the meter does it but I am sure there is some voltage involved from the batteries to work out resistance. No need to have it plugged in and ON when testing out volts and your fingers far away from the metal ends.

 

You can get bogus reading sometimes, I was told it's a good idea to disconnect the neutral from the element if it is telling you something that seems way off.

 

You can test to see how far the elements resistance is away from brand new, just need to know what the brand new element resistance should be.

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celia, you painted the rust on the KILN, not the bowl, right??? recently some black spots have appeared on (naturally, only the white ones) several pots. cannot figure out what they can be but i have ordered some of L&L's brush on finish for the inside of the lid. the spots only happen on the top shelf.

 

Yes Old Lady - on the kiln!!! The black flecks are still on the bowl!

post-13648-0-30795900-1441784008_thumb.jpg

 

Joel - I think I need an electrician friend for this. If I get on to it I'll let you know the outcome.

post-13648-0-30795900-1441784008_thumb.jpg

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Hi,

Not sure if this topic is still alive or not but...

I have a Cromartie Hobbytech 40 which was rated at 1260 on 13amp. It struggled to get to top temperature and certainly wore out the elements in doing so. After speaking with Cromartie I ended up buying new elements rated at 16amp and hard wiring into cooker socket. It happily reaches 1260 now.

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Hi,

Not sure if this topic is still alive or not but...

I have a Cromartie Hobbytech 40 which was rated at 1260 on 13amp. It struggled to get to top temperature and certainly wore out the elements in doing so. After speaking with Cromartie I ended up buying new elements rated at 16amp and hard wiring into cooker socket. It happily reaches 1260 now.

 

I think they are at the very top of size you can run on 13 amps and get cone10 so it will struggle over time as elements degrade. Good to know it works well upgrading to 16 amp elements. 

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Thanks for that info, however I found a great kiln man and as I need to do at least 40 firings  a year to stoneware and he knows his stuff and said a cromartie hobby just could not produch the reliability I needed I have just invested in a new German kiln that will do what I need without bother. As I have loads of orders relying on my work arriving I needed to know I could rely 100% on my kiln. Glad you got it to work for you though and thanks for posting

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On 12/13/2015 at 1:19 PM, CeramicChris said:

Hi,

Not sure if this topic is still alive or not but...

I have a Cromartie Hobbytech 40 which was rated at 1260 on 13amp. It struggled to get to top temperature and certainly wore out the elements in doing so. After speaking with Cromartie I ended up buying new elements rated at 16amp and hard wiring into cooker socket. It happily reaches 1260 now.

Hi Chris,

I recently have bought a Cromartie Hobbytech 40. But it doesn’t seem to work as well as i expected. I’m not sure if it’s something I’m not doing right. So I hope that you or someone els might help me.

The Energyregulator has 6 main positions. See the image. When the number 0 is on top, the little light goes on. Then I turn it to ON and from ON to the number 1. Then the light goes off. And it doesn’t seem to work any more. Although the spirals get a little warm, but not hot at all. Can anyone help me with this? Thanks.

A778321A-0EF2-41CC-A963-C04CB9C5B736.jpeg

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