Jump to content

Recommended Posts

My friend and I recently bought a used kiln and wheel.

Our first test with the kiln we messed up and fired our stuff to cone 6 (instead of 06). We hadn't had a lot in the kiln, just a few really small cut-out pieces. It took about 6.5 hours to get close to cone 6, but the large 6 cone didn't fully drop, and the cone 7 didn't really move much, so we weren't totally sure if it was fully done.

Moving on to our second fire. We had new things to fire, so we bisque fired our stuff (half full with things stacked) to cone 06 this time. Our cone sitter fell out when we closed it (not sure exactly what happened), so after 6.5 hours, we stopped it. We again weren't 100% sure if things we underfired, overfired, or totally perfect. We tried the "lick" test and it was sticking to our tongue. We decided to glaze it and fire to completion. This time, our kiln was full. We didn't put anything on our bottom level (we were worried out glaze would run and it would ruin the kiln). We put in a cone 7 sitter (to make sure it fired completely to cone 6) and we had our large cones to watch at the top and bottom of our kiln. After almost 11 hours, it still wasn't complete (and it was 1am) so we turned it off and left it.

So now I'm left with a million questions.

1) How can I tell if it is completely fired?

2) Can I re-fire the stuff and would I have to fire it from start, another 12+ hours?

3) I've read a million posts talking about different kiln lengths, but I'm wondering how exactly you can tell how long it would take?

4) I think our bottom heat isn't as strong as our tops, so should I be putting thinner stuff at the bottom? Or just get the heaters fixed?

5) If our bisque fire wasn't fully fired, would that make our glaze fire take longer?

 

Thanks so much for any help! Already this website has been a huge help for my friend and I. We basically use this as a pottery bible.

UPDATE!!

We re-fired our glaze and this time everything went off after 8 hours. The glaze is a little runny, but our main concern is the bottom elements not being the best. We had our thin stuff at the bottom, and it did glaze over, but the cones didn't change at all. The top cones did, though! 

Edited by cml
Added more information

Share this post


Link to post
Share on other sites

I would check the elements. Sounds like your first ^6 firing was loaded lightly but your second ^6 was a full load (except for the bottom) and the kiln struggled trying to reach ^6. Was the firing schedule the same for the first and second ^6 firings? Sounds like you have a manual kiln, how long was the kiln on high for? 11 hours is a long time to get to ^6 if there was no candling at the beginning. What is your kiln rated to fire to?

"How can I tell if it is completely fired?" Did you use a ^5 in your cone pack and did it bend at all? How much is the ^6 bent in the cone pack?

Yes, you can refire but glazes might run. Put a thin waste slab of clay under the pots to protect your shelves and kiln wash on your shelves.

Bisque firing won’t have any effect on the length of time the glaze firing takes.

"Our cone sitter fell out when we closed it (not sure exactly what happened) Do you mean the cone fell out of the sitter? As well as checking the elements I would check the sitter is working and adjusted as it should be.

"We didn't put anything on our bottom level (we were worried out glaze would run and it would ruin the kiln)" Use 1/2" or 1" posts to put the bottom shelf on. 

Welcome to the forum:)

Edited by Min
added a thought

Share this post


Link to post
Share on other sites

First, what brand and model is the kiln? What voltage and phase does it need?

Check your elements. Put a cone in (doesn't matter which), turn all the elements on high, and after 10 minutes or so (maybe less) carefully crack the lid and see if all the elements are glowing. Depending on the kiln, the very top and very bottom element may glow sooner and hotter than the others. If one isn't glowing, then either the element is broken, or a connection in the control box is fried. If a pair of elements aren't glowing, then you may have a bad switch. There are other possible causes, but those are the most likely. If they all glow but the kiln isn't getting hot, then the elements are probably worn.

Share this post


Link to post
Share on other sites

When I buy a used kiln I always budget in new elements for it,  they usually need rewired.   Kiln sitters also need maintenance,  I have replace many parts in the sitter over the years.   Do you know how old the kiln is and how much it was used?     Denice

Share this post


Link to post
Share on other sites

those times sound really fast for me.  but maybe you are talking about a very small kiln.  what are its measurements, in inches wide and deep.  number of square feet means nothing to me.

what instructions do you have for firing, anything written by the kiln manufacturer?  are you just turning the switch(s) to high and walking away?

watching videos is lots of fun but they are not available as a reference when you are firing.  this forum has a lot of info if you can find it.  what you really need is a good quality textbook kind of guide.  something with a lot of instructions, not just a "this is how to make this one thing" book.

Share this post


Link to post
Share on other sites
20 hours ago, cml said:

We didn't put anything on our bottom level (we were worried out glaze would run and it would ruin the kiln).

 

Ya know I'm not sure your loading the kiln correctly. I usually use my one inch post for my bottom shelf. Since you mention glaze running ruining your kiln I am reading it as you view the absolute bottom of the kiln as an option. I could be mis-reading, since what you say is correct about ruining it on glaze melts, but want to make sure you aren't using normal post and leaving some huge empty gap at bottom.

If I were you I would stop and do 2 more test firings with all empty shelves and a cone pack on each shelf. The pack should be one cone lower, desired cone and then one cone higher. The lower cone should bend all the way over, the desired half to full and the one cone higher should not bend at all.   Make a log and record the results or both bisque and glaze on each shelf and note exact time that kiln sitter cone dropped and as an added I would note time to cool (although all of these times will change with full/half full load).

Then at least you have the times and cone temps reached on each shelf. Using that information along with size of kiln I think people here can help determine if you have a problem and you will also know if there is a variance between shelves that may or may not need to be addressed.

Elements supposedly last about 150 combined firings so that's about 75 bisque and 75 glaze if you do one of each each time. As elements age it takes longer to fire and eventually they will not reach temperature.  if you start keeping a log then you can see where they are at now and as they age you can see the progression and make a decision at some point on if its time for new elements.

I think the main thing right now is be methodical, take notes, make sure your shelves have kiln wash for glazing.

have fun!

Edited by Stephen

Share this post


Link to post
Share on other sites
On 8/20/2018 at 4:24 PM, Min said:
Quote

I would check the elements. Sounds like your first ^6 firing was loaded lightly but your second ^6 was a full load (except for the bottom) and the kiln struggled trying to reach ^6. Was the firing schedule the same for the first and second ^6 firings? Sounds like you have a manual kiln, how long was the kiln on high for? 11 hours is a long time to get to ^6 if there was no candling at the beginning. What is your kiln rated to fire to?

I have an Evenheat 5320, 7200 watts. We think our bottom element isn't working well, so we are in the process of getting that looked at/replaced. 

Quote

"How can I tell if it is completely fired?" Did you use a ^5 in your cone pack and did it bend at all? How much is the ^6 bent in the cone pack?

We used a ^5, 6, and 7. The ^5 completely folded, and the six did too. The 7 didn't really, but it did glaze. This only happened on our top shelf, not the bottom shelf. The bottom shelf didn't really do anything. 

Quote

""Our cone sitter fell out when we closed it (not sure exactly what happened) Do you mean the cone fell out of the sitter? As well as checking the elements I would check the sitter is working and adjusted as it should be."

Our cone sitter works fine, I must have knocked it out when I was moving things around and hadn't noticed. 

"Welcome to the forum:)" THANKS! I am so excited to start this journey!

 

Share this post


Link to post
Share on other sites
On 8/21/2018 at 9:49 AM, Denice said:

When I buy a used kiln I always budget in new elements for it,  they usually need rewired.   Kiln sitters also need maintenance,  I have replace many parts in the sitter over the years.   Do you know how old the kiln is and how much it was used?     Denice

Thanks, Denice. The person we bought it from did plate painting stuff, so she didn't fire as high as we are. I don't know how old it was, but I know she used it lots for a while, but stopped for some time before selling it. She said she would need to do like 20 firings per plate, but again not to the ^6 we are. 

I think our bottom elements will need to be done, but the rest seem to be good!

Share this post


Link to post
Share on other sites
On 8/21/2018 at 11:16 AM, Stephen said:
Quote

Ya know I'm not sure your loading the kiln correctly. I usually use my one inch post for my bottom shelf. Since you mention glaze running ruining your kiln I am reading it as you view the absolute bottom of the kiln as an option. I could be mis-reading, since what you say is correct about ruining it on glaze melts, but want to make sure you aren't using normal post and leaving some huge empty gap at bottom.

Thanks! That was super helpful, we had no clue! Is this the same for a bisque firing, or is it just the glaze firings to avoid glaze running?

Quote

If I were you I would stop and do 2 more test firings with all empty shelves and a cone pack on each shelf. The pack should be one cone lower, desired cone and then one cone higher. The lower cone should bend all the way over, the desired half to full and the one cone higher should not bend at all.   Make a log and record the results or both bisque and glaze on each shelf and note exact time that kiln sitter cone dropped and as an added I would note time to cool (although all of these times will change with full/half full load).

Good plan. We didn't care much about the stuff we made, so this is basically us testing it. We have been keeping diligent notes on everything to make sure we are able to keep track of everything. 

Quote

Elements supposedly last about 150 combined firings so that's about 75 bisque and 75 glaze if you do one of each each time. As elements age it takes longer to fire and eventually they will not reach temperature.  if you start keeping a log then you can see where they are at now and as they age you can see the progression and make a decision at some point on if its time for new elements.

I had no idea that elements had a shelf life. Luckily our kiln wasn't all that pricey, so if we have to get new elements that won't be too bad. 

Quote

 

I think the main thing right now is be methodical, take notes, make sure your shelves have kiln wash for glazing.

have fun!

 

Thank you thank you thank you!

Everything has been super helpful. This is so great!

 

Share this post


Link to post
Share on other sites
On 8/21/2018 at 10:11 AM, oldlady said:
Quote

those times sound really fast for me.  but maybe you are talking about a very small kiln.  what are its measurements, in inches wide and deep.  number of square feet means nothing to me.

Our kiln is about 23" wide and about the same depth, maybe a little deeper. 

Quote

 

what instructions do you have for firing, anything written by the kiln manufacturer?  are you just turning the switch(s) to high and walking away?


 

We have the kiln manual from the manufacturer. We have to turn a switch on every hour (5 switches), then we let it go until the cones drop, or our cone sitter turns it off. 

 

 

Share this post


Link to post
Share on other sites

bummer on the bottom element.

We just leave the bottom kiln shelves on the short post in all the time. I would think that weight distribution would be a factor as well so I wouldn't ever put pots directly on the bottom kiln bricks. Also when you add kiln wash only do it on the top and don't over do it. Just an even coat. if you blob it on it will flake off and ruin your pots.

oh as a side note its not uncommon to see small hairline cracks form, particularly on the bottom. Just keep an eye on them and if they start to widen then it may be more serious but even fairly new kilns get them. They make a patch you can use if you ever feel one is troublesome. 

 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×

Important Information

By using this site, you agree to our Terms of Use.