Kiln build / modification - advice needed

[ianperrymccarthy]

Hi all - here is the conundrum:

I am looking for a way to fire large, very tall pots, (let's say up to 2.5' wide, and up to 6' tall), to cone 06, and on the cheap. Gas or wood as preferred heat sources - I'm not well set up for heavy electricity. I've gone through a few ideas, the first being to simply build a tall custom kiln from firebrick to my ideal dimensions. I haven't been able to find any used brick in the region, (western NY), and the cost of new brick might put this out of my range. I've been inspired by Nina Hole's petal kilns, and have started thinking down that route. What I do have on hand is a large electric kiln that I think could serve as the base. If I convert that to gas, stack some firebricks up on the edge to give me the extra height I need, and wrap it all in ceramic fiber blanket... any thoughts from experienced kiln DIYers here? Thanks much!

[Mark C.]

Make the whole kiln out of fiber (pretty cheap stuff)Except the base

make the kiln from a heavy wire like a basket )

gas burners underneath.-propane the base would be brick (soft brick will work fine as well as hard) with the basket over the pot. 

my favorite e-bay vendor sells fiber in many forms-as well as brick

You could getr away with 6# fiber  backup layer as well but this 8# is best for the hot face

this would work great-https://www.ebay.com/itm/143362228317?hash=item21610e005d:g:MiQAAOSwtAlbrOFw

[ianperrymccarthy]

Thanks Mark, that is a very helpful start. Do you have opinion on what is best for the metal structure to support the fiber, and how to join the fiber and structure together? I never got a chance to see a petal kiln in person and figure out how it ticks.

[PeterH]

1 hour ago, ianperrymccarthy said:

Thanks Mark, that is a very helpful start. Do you have opinion on what is best for the metal structure to support the fiber, and how to join the fiber and structure together? I never got a chance to see a petal kiln in person and figure out how it ticks.

I think the 2nd question is [partially?] answered in
Clay Culture: Petal Kiln
https://ceramicartsnetwork.org/ceramics-monthly/clay-tools/ceramic-kilns/clay-culture-petal-kiln/#
Each section of the kiln is a metal frame to which fiber is attached with ceramic buttons.

I'll add a few questions about the framework, based on an image from 1m11s into
The Petal Kiln at The Australian Ceramics Triennale Tasmania 2019 Hobart
https://www.youtube.com/watch?v=yTn9HRRExnI

1) How are the small joining struts constructed. Are they just hollow tube that push into each other?
- No the fact that the uprights are hinged at the bottom suggests that they could be something like a cylinder and a half-cylinder.
- OTOH at about 1m50s into the video they seem to be pulling the joint apart before opening the petals, so maybe it is just one tube inside another with a very short overlap (smaller than the wriggle-room).

2) Are the thin wires twisted between the uprights of different petals the only thing holding them together?

3)The petals are [always?] shown being opened simultaneously. Is this just for dramatic effect, or is it necessary for stability?
 

 

[ianperrymccarthy]

Thank you for the homework done there - and the good questions. I am curious about the 'ceramic buttons' - there is one good picture in the article you linked that gives a glimpse of the round, flat, buttons that are on the inside of the petals. They each have two holes - presumably that have wires going through the holes which tie around the metal bracing in order to connect the fiber? Are those buttons a common item I don't know about, or something custom? What metal would the wire going through the buttons be? 

[Babs]

Could make your own ceramic buttons .

Wire used is Kanthal wire. Can get different weights.

Buttons on my old fiibre kiln were top hat shaped with wide brim. The hat inner was filled with fire cement. I guess to protect the wire from direct flame??

Fire down as these kilns temp drop like a rock.

Roof had more buttons.

Fibre after firing gets fragile and will slump.

Think you can spray it to stop the flaking...dangerous healthwise. Not good to breathe in.

Check Marcia Selsor's top hat kiln.

Block anbd tackle or winch to lift kiln off base

 

[CactusPots]

I take it this purpose is only to last for a few firings.  As cheaply as possible.  So my comments don't apply much to this particular conversation.

My home built fiber downdraft is 20 years old with 60+ firings.

Otherwise, I disapprove of the concept of fiber as a hot face.  As Babs said, fiber gets fragile and it's really delicate at that point, any bump will disturb it.  The coatings don't work well over time as they shrink at a different rate than the fiber.

Looks like I'm going to have to replace the lid sometime soon.  It's 12 inch modules, super insulating, but they are shrinking away from each other leaving gaps for the heat to work on the supporting structure.  Last firing a module moved down half inch and grabbed a pot.  Ouch.

Best use of ceramic fiber is backup material, I think.

Thanks Mark for the Ebay link.

[ianperrymccarthy]

1 hour ago, CactusPots said:

I take it this purpose is only to last for a few firings.  As cheaply as possible.  So my comments don't apply much to this particular conversation.

You know - I was planning on something longer-term. I appreciate the perspective with fiber though. I knew it wouldn't be the most sturdy material, but I definitely want something that will last more than a handful of firing. It seems like opinion is split on fiber generally. 

 

Circling back to an earlier thought I had - stacking blank kiln rings until I reach my desired height. The only ones I could find were either too expensive, included electric elements I don't need, or both. Any source for cheap blank kiln rings, or plans for building your own? A masonry saw is something I have access to.

[Mark C.]

I posted a photo a few years ago on some homemade buttons-check out my photos or search the whole site for buttons. 

My piece on buttons is here

Here is a raku button in this piece. 

 

[Min]

41 minutes ago, ianperrymccarthy said:

Circling back to an earlier thought I had - stacking blank kiln rings until I reach my desired height. The only ones I could find were either too expensive, included electric elements I don't need, or both. Any source for cheap blank kiln rings, or plans for building your own? A masonry saw is something I have access to.

If you go this route there is a really good article here about converting an electric kiln to gas, covers burner ports, draft, flu etc.

Finding some trashed kilns right now is going to be the hard part, used equipment is getting snapped up really fast due to the pandemic.

[Mark C.]

You can make the outer frame from hog wire-Heavy wire in square pattern or sheet metal . Wire lasts longer I feel as it does not trap heat.The whole kilns needs to be kept dry at all times (no rain on fiber)