neilestrick

Yes to all 

Yes, an empty firing will build build up a layer of oxidation on the surface of the elements, which will help protect the metal from fumes in future firings. The hotter the better, but generally a bisque firing will do the job. It's also a good idea to put some cones in the kiln to make sure everything's working properly with the new elements.

Yes to all 

In my experience, they may or may not warp back. Doesn't hurt to try, though. Just make sure they're really clean on the bottom so they don't drop stuff onto your pots.

If you do an absorption test on your clay it will tell you this. It's a good idea to test a claybody for absorption using your kiln and firing methods rather than what a clay manufacturer publishes it as. For functional ware below 1 - 1.5% is usually good. Link here on testing absorption if you need it. If the clay isn't porous for all intents and purposes and you run your pots through the dishwasher I wouldn't worry about the odd pinhole. Aesthetics are a different point, a pinhole on a pristine porcelain piece is going to stand out far more than one on a rustic piece. 
Ryan Coppage article here discussing bacteria growth on crazed glazes. Conclusion is if your clay is vitrified and the pots run through a dishwasher bacteria is not an issue. (article is behind a paywall but you can access 3 free articles a month) I haven't come across any literature proving pinholes harbour more bacteria than craze lines.

It would be faster and better to just roll a new slab. Paperclay joints on bone dry pieces are not always 100% successful, especially on a thin slab. If you're bisque firing, pieces will not stick together unless you've properly joined them with slip/score.

Hi everybody
Tried out some commercial available hollow dies in the small clay saver
They are well made the hollow clay tubes came out amazing.
When I made  this  extruder no  welding was used
It all bolted  together  ,
I have made a small alteration the ball joint socket has been extended and is fixed in place with some bolts
I will draw up some plans on how to make this extruder some time next year,
Mick

It would be faster and better to just roll a new slab. Paperclay joints on bone dry pieces are not always 100% successful, especially on a thin slab. If you're bisque firing, pieces will not stick together unless you've properly joined them with slip/score.

It would be faster and better to just roll a new slab. Paperclay joints on bone dry pieces are not always 100% successful, especially on a thin slab. If you're bisque firing, pieces will not stick together unless you've properly joined them with slip/score.

@Mark C. The L&L stand has a full metal top:

Those cracks are probably nothing to worry about. Hairline cracks are perfectly normal in the floor slab, especially in 28" kilns. Since the L&L kiln stand has a solid top that supports the floor very well, even if the cracks open up a bit it's not going to matter. Just be sure to keep the metal band around the slab tight, and also tighten up all the other bands while you're at it.

I have never seen the direction of the wedging to have any effect on my throwing or any of my students' throwing. Once you cone the clay a couple of times during centering, any wedging spiral is gone. IMO she is overthinking the process, or finding something to blame for poor centering technique. I have wedged 'backwards' of the way she's showing for 30 years, and I've never had any issues. Same with my students. Wedge it, make it into a ball, smack it onto the wheelhead, and center it. With good coning technique it doesn't matter which way it was wedged.

The clear relays run hot because the box that they're in is shallow. You'll notice on the top that there are 5 louvers. They switched to the black relays at some point, presumably because they were cheaper, and found that they burned out really fast, so they made the box deeper (6 louvers) to provide more air flow, and it made more room for the wire terminals so they didn't have to use right angle terminals with those relays. They recommend still using the clear relays in the 5 louver boxes. The clear ones are rated for high heat areas, and in general they do pretty well.
@Hyn Patty You need a new wiring harness. You've still got the original 20 year old wires connected to the relays, and they are most likely what is causing them to overheat. I see this all the time in Skutt kilns, and new wires solve the problem. Transformers rarely fail, and I don't see how it could cause the relay to fail, but as long as you have one coming, go ahead and replace it and all the wiring in the box at the same time.

@Mark C. The L&L stand has a full metal top:

@Mark C. The L&L stand has a full metal top:

Those cracks are probably nothing to worry about. Hairline cracks are perfectly normal in the floor slab, especially in 28" kilns. Since the L&L kiln stand has a solid top that supports the floor very well, even if the cracks open up a bit it's not going to matter. Just be sure to keep the metal band around the slab tight, and also tighten up all the other bands while you're at it.

Hi Neil, yes both those are possibilities. It will take me a couple of weeks to install an inline valve and re-test, and then come back to the forum with success or failure. Thanks for all the suggestions.

You can't replace the relays with anything different. There are other types that will fit, but the ones you have are made for high heat locations. They're the best you can do. And for the most part they will work fine. The only other option is to get a new control box and move everything over to it and use the black relays. I don't think that's necessary, though.
I've seen relays fail prematurely on Skutt kilns dozens of times, and the solution, per Skutt, is to change the wiring harness.

I have never seen the direction of the wedging to have any effect on my throwing or any of my students' throwing. Once you cone the clay a couple of times during centering, any wedging spiral is gone. IMO she is overthinking the process, or finding something to blame for poor centering technique. I have wedged 'backwards' of the way she's showing for 30 years, and I've never had any issues. Same with my students. Wedge it, make it into a ball, smack it onto the wheelhead, and center it. With good coning technique it doesn't matter which way it was wedged.

You can't replace the relays with anything different. There are other types that will fit, but the ones you have are made for high heat locations. They're the best you can do. And for the most part they will work fine. The only other option is to get a new control box and move everything over to it and use the black relays. I don't think that's necessary, though.
I've seen relays fail prematurely on Skutt kilns dozens of times, and the solution, per Skutt, is to change the wiring harness.

The clear relays run hot because the box that they're in is shallow. You'll notice on the top that there are 5 louvers. They switched to the black relays at some point, presumably because they were cheaper, and found that they burned out really fast, so they made the box deeper (6 louvers) to provide more air flow, and it made more room for the wire terminals so they didn't have to use right angle terminals with those relays. They recommend still using the clear relays in the 5 louver boxes. The clear ones are rated for high heat areas, and in general they do pretty well.
@Hyn Patty You need a new wiring harness. You've still got the original 20 year old wires connected to the relays, and they are most likely what is causing them to overheat. I see this all the time in Skutt kilns, and new wires solve the problem. Transformers rarely fail, and I don't see how it could cause the relay to fail, but as long as you have one coming, go ahead and replace it and all the wiring in the box at the same time.

If it's a throwing class, why are they taking more students than wheels? The mixed levels is not a problem at all. Every class I've ever taken or taught  has been mixed levels. I think it's great, because the advanced students pass a lot of knowledge down to the beginners. But for the class to really work well you need everyone to have a wheel.

The clay suppliers cannot control the quality of their raw materials, nor can they test each bag of raw materials, nor can they really inspect every batch of clay to find chunks in it, especially if the chunks not a certain percentage of the mix. It would be impossible to find them. They rely on their raw materials suppliers to provide quality materials, and they take a risk with every batch of clay they make. But it's they're job to acknowledge that there's a problem and make it right, either through refund or replacement, just like the raw materials suppliers will have to do for them. That's all they can do- be nice about it and make it right. If they can't do that, I would consider finding another supplier (I know that's not a simple thing). Clay is cheap, even when it's expensive, and replacing one ton isn't going to hurt their bottom line at all when they're selling a few million pounds a year.
I used to run the clay production lines at A.R.T. clay, and if we found a problem that was not the fault of the potter, we would replace the clay body. One person who bought 100 pounds and had a problem is probably not the clay's fault. Several reports from different studios is probably a clay problem. Chunks of rock would definitely fall into the replacement category, regardless of how many people found it. We once found a hole in the stainless steel liner of our mixer, meaning there was a quarter-sized piece of metal (or several smaller pieces) somewhere in the clay. Bad news. We had to throw out all the clay we had mixed since we last cleaned out the mixer completely and knew there wasn't a hole in it, something like 12,000 pounds.

The clear relays run hot because the box that they're in is shallow. You'll notice on the top that there are 5 louvers. They switched to the black relays at some point, presumably because they were cheaper, and found that they burned out really fast, so they made the box deeper (6 louvers) to provide more air flow, and it made more room for the wire terminals so they didn't have to use right angle terminals with those relays. They recommend still using the clear relays in the 5 louver boxes. The clear ones are rated for high heat areas, and in general they do pretty well.
@Hyn Patty You need a new wiring harness. You've still got the original 20 year old wires connected to the relays, and they are most likely what is causing them to overheat. I see this all the time in Skutt kilns, and new wires solve the problem. Transformers rarely fail, and I don't see how it could cause the relay to fail, but as long as you have one coming, go ahead and replace it and all the wiring in the box at the same time.

I have never seen the direction of the wedging to have any effect on my throwing or any of my students' throwing. Once you cone the clay a couple of times during centering, any wedging spiral is gone. IMO she is overthinking the process, or finding something to blame for poor centering technique. I have wedged 'backwards' of the way she's showing for 30 years, and I've never had any issues. Same with my students. Wedge it, make it into a ball, smack it onto the wheelhead, and center it. With good coning technique it doesn't matter which way it was wedged.