Electric Bisque 06

[CactusPots]

I've been firing with the lid open about 3" until 400F.  The idea is to burn out the water and organics.  Then close the lid and fire with the top plug out.  I'm noticing pretty substantial corrosion on the one year old lid band from the exhaust out the top plug.  I suspect something like sulphur  burns out higher than 400.  Yes?  Best practice?

What would be considered a safe ramp speed through quartz inversion?  I'm talking max size the kiln will handle.

[Sorcery]

Digital Fire has a thing about organics not burning out all the way until 1900F.

I believe a slow ramp up also needs a slow ramp down.

What is the end of your firing like?

I have been reading about crash cooling the first couple hundred degrees to prevent crystabolite formation. Something about holds allowing it to form more. That's what cracks at 473F coming down if I'm not mistaken.

I wonder of you're not burning out all the organics on bisque. The only firing (single fire) I've had where things were 100 spent 9hours through 1000F-1900F.  A hundred ramp? It was probably closer to 240/hr tapering to 60/hr, repeated.

Firings that spent less time through burnout have created weak, carbon cored wares.

Sorce

[Mark C.]

All the organics can rust the heck of the kiln jackets. I also prop the lid but my main body jackets failed as well over 25 years not just the lid band. Clay fumes are harsh and there is no way around that.

[GEP]

I use an overhead vent hood, and keep my top peep holes open all the time. I have corrosion on the lid band just above the peep hole too. My kilns are 16 and 7 years old, and get used heavily. They don’t seem to be anywhere close to failing yet, so the corrosion doesn’t bother me. 

[neilestrick]

Corrosion is normal, and will take a really long time to corrode through the metal. The best way to minimize it is to use a downdraft vent. It's primarily an aesthetic issue, but the connections in the control box tend to corrode more quickly in non-downdraft-vented kilns, too.

[CactusPots]

It took around ( 3 glaze per year, 7 bisque per glaze, 18 or so years) 400 bisque loads, but the original lid band did in fact fail.  That's a bad thing, because it will fail as you go to lift the lid and the lid will then fracture.  Better to replace the lid band while the lid is in one piece.

So without a kiln vent, what is the recommended procedure for minimizing exhaust corrosion?    I have been firing with a brick cracking the lid until 400 then finishing with the top plug out.

Anyone else?

[CactusPots]

On 10/11/2020 at 8:55 AM, GEP said:

I use an overhead vent hood, and keep my top peep holes open all the time. I have corrosion on the lid band just above the peep hole too. My kilns are 16 and 7 years old, and get used heavily. They don’t seem to be anywhere close to failing yet, so the corrosion doesn’t bother me. 

You do want to keep an eye on that.  It's easy to forget about it until it's too late.  I'd recommend replacing the band when the bottom edge shows actual loss of material, not just surface rust.