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Aloha All,

Just fired up Black Bertha for the second time.

First fire was 75 dph to 1500 to steam out the mizu table. 42 hour up and down.

Second fire was to 1375 to fuse to stick some glass.

Problem:
Third ramp was 960 to 75 in 4 hours.
Actual time to 75 was 27 hours. Not much good for daily production.

Dim of table 53 x 102
3 3/4" 23K IFB
1 1/2 - 3K Mizu

Bell 43 x 92 interior 53 x 102 exterior
4" all surfaces - Super K Wool
1" Skamol Board - all surfaces

I'm open to ideas - It appears to me the table is the problem - but I wanted another opinion before I rip out the mizu and replace it with three more inches of brick.

Or am I being impatient and there is still water in the casting an it will take a few more full temp fires to dry it out.

Lionel wrote:Aloha All,

Just fired up Black Bertha for the second time.

First fire was 75 dph to 1500 to steam out the mizu table. 42 hour up and down.

Second fire was to 1375 to fuse to stick some glass.

Problem:
Third ramp was 960 to 75 in 4 hours.
Actual time to 75 was 27 hours. Not much good for daily production.

Dim of table 53 x 102
3 3/4" 23K IFB
1 1/2 - 3K Mizu

Bell 43 x 92 interior 53 x 102 exterior
4" all surfaces - Super K Wool
1" Skamol Board - all surfaces

I'm open to ideas - It appears to me the table is the problem - but I wanted another opinion before I rip out the mizu and replace it with three more inches of brick.

Or am I being impatient and there is still water in the casting an it will take a few more full temp fires to dry it out.

Bungs in ?

Lid closed properly ?

Check elements

Have kiln cold turn on full for few mins, get wood stick tie cloth on end , wet cloth but stick dry

Turn off kiln

Elements work that sizzzz when touched

My guess is either not enough power 2 kiln / not enough elements

Or whole bank of elements not working

Brian

I've said it before, if you want to do a 24 hour cycle it's better to have an under-insulated and over-powered kiln. I'm not familiar with Mizzou, so I don't know if it is adding more mass or more insulation. Either way, an inch and a half is a lot, and it is slowing down the cool down.

For a sand bed kiln, which adds about 3/4 inches of sand to the bottom of the kiln, (which I believe is more mass than insulation), I would have, at most, 4 inches of fiber insulation in the bell. I would have, at most, three inches of IFB in the table. In addition I would have an open grating under the IFB rather than solid steel. This is how Warren Langley has his kilns built, and he has been doing this for thirty years.

ch

If I pull the boards out of the bell that would make it 45x94x10 or 24.47 cubic feet.

Currently there is 20.6 cubic feet.

I have 21208 total watts or 1029.5 watts per cubic foot

After pulling the boards that would reduce to 866.6 watts per cubic foot.

Will I have enough power to avoid devit at the higher end?

What is the minimum acceptable watts per cubic foot?

On the table - the sheet metal base is welded and can not be removed.
What if I pull everything out and put 2 1/2 inches of sand and one layer of 2 1/2 inch IFB on the sand? We have lots of free sand here!

I read somewhere that there is one kiln company that puts copper 1" tubes in the table base every six inches and uses forced air for cool down - any thoughts?

Thanks -

Aloha,
seems part of the pilikia for cooling quicker could be in the table... I don't know what the Mizu is but the IFB bricks being denser will still hold alot more heat than Kaowool on the base/table. A lot of sand will add more mass = longer cooling time

I used about 6in thick Kaowool for table/base (yeah, over kill but we had it handy and affordable) with IFBricks inserted up on end to use as kiln shelf supports. Air circulates under and helps with even firings and to get the heat out when cooling. This Kilns' internal firing surface is 4 x 6 foot with about a 3 inch gap around edges. With the floor elevated you can lift the Lid (inverted shoebox) and get some air under to crash cool if you so desire or really speed things up once you get past all the important temp. danger zones

Before you rip up the table flooring... What size bungs and where are they located? I made 4 huge (5 inch dia) in top of lid to help cooling.. Oh and a mother of a spyhole for peeking in from the side. Perhaps this could be causing a bit of pilikia too!
Like to hear your results.
Victoria in Australia (ex-Kona girl)

Putting on my stupid hat .......

What are bungs ?

Do I neet top vents in this thing ?

Hey where are all the "B " Boys? Brad Brock Bert

Feel free to chime in - I need to dial this puppy in - in under 2 weeks.

Lionel wrote:Putting on my stupid hat .......

What are bungs ?

Do I neet top vents in this thing ?

Hey where are all the "B " Boys? Brad Brock Bert

Feel free to chime in - I need to dial this puppy in - in under 2 weeks.

Bungs are the things that go in bung holes/viewing ports/vents. I haven't really been following this Lionel, is your kiln a top hat/bell? If so, I've found on the bigger ones, raising the lid is a good way of venting, if you have no other.

Fibre Good/Brick Bad

Large brick kilns take forever to come down. They may be okay for use as annealers for blowers, but it's difficult to get rid of all the heat of fusing temps. You may have to reduce your insulation

Phil, are you listening?

Brock

Lionel-I've got two bell kilns with comparable cubic footage to yours, elements in ceiling. Ceiling has 1" board, 5" fiber batt, sides 1" board, 3" batt, and floor is two layers of soft brick. Wattage is about 15K. I use them for production and easily get 24 hour cycles, the usual is more like 12 to 16. I vent at about 400F, and open at 180 for most of the work. No vents or bungs. I'm not familiar with the castable you used for the floor, but it does sound like you have some high mass down there. I'd put some soft brick on the sheet metal, and some shelves on that.

Tony - Are you saying that 15000 watts or 612 watts per cubic foot get you to 1450 in under 3 hours?

Is your board on the hot surface or the outside?

Two layers of brick would be 5" or are you using 3" brick?

Do you use many small kiln shelves or one large one?

I casted the mizu to be the kiln shelf but in retrospect 1 1/4 was way over.

Brock - I never had to vent my small Paragons. What is the safe zone to lift the lid and what is a safe drop rate for BE and plate?

Brock - I never had to vent my small Paragons. What is the safe zone to lift the lid and what is a safe drop rate for BE and plate?

You don't have to vent your Paragons because they don't have the huge thermal mass that this kiln has. I cannot predict a safe drop rate for your kiln, but you could be venting as high as 500, or more, depending how slightly you can raise the lid.

Lionel wrote:Aloha All,

Just fired up Black Bertha for the second time.

First fire was 75 dph to 1500 to steam out the mizu table. 42 hour up and down.

Second fire was to 1375 to fuse to stick some glass.

Problem:
Third ramp was 960 to 75 in 4 hours.
Actual time to 75 was 27 hours. Not much good for daily production.

Dim of table 53 x 102
3 3/4" 23K IFB
1 1/2 - 3K Mizu

Bell 43 x 92 interior 53 x 102 exterior
4" all surfaces - Super K Wool
1" Skamol Board - all surfaces

I'm open to ideas - It appears to me the table is the problem - but I wanted another opinion before I rip out the mizu and replace it with three more inches of brick.

Or am I being impatient and there is still water in the casting an it will take a few more full temp fires to dry it out.

I have read this wrong ur Q is a cooling down one ??

I dont know about copper pipe but stainless pipes buried in the insulation then air blown down em after aneal would help

The less thermal mass U got in the kiln during the cool ( after aneal )would help

A consideration mayB 2 remove some insulation after aneal

Or have pipes on top of the kiln then blowing this warm air gently in2 the bottom of the kiln

I recall I think Henry Halem discribing some air cooled method

Might have been over craftweb

Whatever U do avoid cold air comming on2 the glass during the cool after aneal

Evenivity is the key

This after aneal cool is a real problem as so easy 2 get thermal shock at this time

Brian

Lionel-I can get to 1450 in about an hour. The board is to the interior, and yes I am using 2 1/2" thick brick, for a total floor thickness of 5". I use 20 x 20" mullite shelves and deal with the seams in various ways. In theory a cast floor sounds like a good idea, but I suspect there would be problems with cracking sooner rather than later.

Lionel

I would not tear out the insulation boards in the Bell. Your problem is the floor.

I use 5" (2 layers)of 2300º IFB for my floor. It is then covered with multiple layers of blanket and LD boards. I am thinking about removing the blanket and possibly a layer of brick and adding an inch or 2 of Vermiculite board for my sand bed.

I would have tried maybe a skim coat of Mizzou, but 1.75" seems like a great deal of unnecessary mass to heat and cool.

I think of 800 - 1000 watts per cubic foot as being right. I have heard of people with as little as 600 getting to temp. Just not quickly.

I don't have any bung holes in my roof, but it seems like a pretty good idea. The Italian kiln I used had 4. I think the trick is to get Mullite shapes that are either cone shaped or wedge shaped so they fit well and are easy to remove. I would worry about IFB raining crud down. If anybody knows a source for these shapes, please let us know.

the bung plugs for my skutt are cone shaped.

Bert Weiss wrote:I think the trick is to get Mullite shapes that are either cone shaped or wedge shaped so they fit well and are easy to remove. I would worry about IFB raining crud down. If anybody knows a source for these shapes, please let us know.

Pottery supply stores and kiln manufacturers, as well as art supply places like Dick Blick, all carry peephole plugs. Most are cone shaped. Should be around $3 each.

Thermal mass is the problem. You pay to heat it and then wait to cool it. Wasted money and time. I hate my kiiln shelves as they add mass to my kilns. I could fire faster without them. Mine run 6 cubic ft on 2300 watts.
It is not the power going into a kiln that is important, it is what you are heating and cooling in the kiln. Kevin

The bung holes/cooling port inserts/sleeves:

I had a local potter throw long cylinder shapes with a 1 1/2 inch flange/lip at the top and open at the bottom which tapers gently narrowing at the bottom! (So the bung/plug won't fall thru. )
These can be what ever dia. you desire. The length needs to be at least the thickness of the inner (insulation or heat face) and outer skin of the kiln. The flange rests on the outside skin of kiln.

The insert need to be made from at least a Raku clay which handles thermal change without breaking. We used Keanes White Raku as it doesn't have a lot of 'grog' in it so the potters won't bleed throwing rough clay. Ideally the clay can be mixed with 10% 200 mesh pearlite and 10% Zircon flour. Fire to stoneware (at least 1100 C) you need to allow for 10% shrinkage.
The thickness of the clay insert around 5/8 inch. (10mm)

If you are putting these bung holes in the lid of the kiln and your elements are also in the lid its best to avoid placing the holes directly over the elements.

After you've cut the holes (I'm assuming the lid is fibre) De-laminate a square of fiber blanket at least 1 1/2 inches bigger than the hole and compress (stand on it) to make a gasket. (1/4 inch thick) . Trim any 90 degree edges of fiber as it sticks better. You can also cut a fiber gasket to fit between where the clay insert flange meets the outer metal kiln skin.
Once you've got all your bits and piece cut and ready just use the fibre cement to glue bung hole insert and gaskets.
Its a good idea to pack in scrap fiber around the clay insert so it is snug. before adhering a gasket on the inner heat face to stop the heat from running up the clay insert to the metal outer skin of kiln and to stop fibre from dropping on to your work is a good thing.
.
For the bungs aka the plugs... You can roll up fibre and rigidize.... (same process as making slumping molds ) to custom fit a taper shaped cone for each bung hole. 0r just use thick fibre blanket/wool over the holes. Less fallout than using carved up soft kiln brick.
HAppy cooking!

Thanks All -

I'm ripping out the mizu today and relining with soft brick.

I'll post an update after I fire.