3" Brick Versus 2.5"

[Stephen]

I'm adding a 2nd kiln primarily for bisque, although it will pull some glaze duty occasionally, Cone 04 bisque and cone 6 glaze. I am getting the Skutt KM1027 and trying to decide on the brick size. This is the largest kiln I can work into the spot we have for it. I have no doubt the 3" inch brick has plenty of pros as more efficient but it also removes 1/2 a cf kiln space. Since I really need space over saving a little on energy and element life I was going to go with the 2.5" brick. My salesman is pushing 3" brick if I fire to cone 6.

 

Is it really worth giving up the space to get the 3" brick? How much does it really save?

[neilestrick]

There is a noticeable difference in the amount of heat coming off the different brick thicknesses. If you look at the heat loss BTU calculations, you're going to have about 17% less heat coming off the 3" brick, so it's going to cost you a dollar or two per firing to go with the 2.5". Even with an extra firing every 14 firings to make up for the size loss, it's cheaper to fire the 3" kiln than the 2.5" kiln. If you add in the element life, it's going to save even more to go with the 3" brick. There's also some added durability in having the thicker brick.

 

Do you already have a kiln of this size and would like to use the same shelves?

 

If you went with an L&L you could get 6.7 cubic feet instead of 6.4.

[Stephen]

Thanks Neil! We have a larger Crucible 8.6 cf oval so no need to match shelves and based on what you said I guess its worth it to lose the space for the 3" brick upgrade. The new kiln will be next to the throwing/drying stations so the extra heat the 2.5" brick puts off will make that even more of an issue than it is already going to be when firing and drying at the same time. I do have a damp rack so there is that.

 

It was close but decided to go with the Skutt KM1027 this time.

 

Thanks!

[MatthewV]

If the question is economics the essential question is How often will you glaze fire in this kiln?

 

I am a long-run type person and would also recommend the thicker walls.

[neilestrick]

If you're going to be working anywhere near the kiln while it's running, you want the thicker walls.

 

What's you plan for venting? With two kilns you may want to add in a wall fan or something to cool the space.

[Stephen]

I am installing a vent and it will be firing after hours when no one is working in the room beyond maybe the first couple of hours on ramp if candling at all.

 

The other kiln is in another building so its not going to be a factor.

 

Overall it does sound like the pros of 3" brick are worth the loss of space so I'm going with the 3" brick.

[Mark C.]

The 3 inch is the way to go no matter what you are doing in my view.

I have owned 2 2.5 inch and one 3 inch and would never go back to 2.5..

3 really is the minimum.

Hey I only bisque in mine and I'm saying this.

As Neil said the jacket is so much hotter in that thin wall.

[oldlady]

this is why i have a problem with the use of cubic feet to describe the space inside a kiln.  what really matters is how big the item on the shelf is and will the shelf fit inside the kiln with room for fingers to lift it in and out. horizontal inches, vertical inches make more sense to me than cubic inches.  who thinks in cubes?

 

mark, don't post a picture done by any cubist artists!

[Mark C.]

Old lady not to worry now that Cuba is opening up cubist are going to be less rare

[glazenerd]

3" minimum for me personally. Everyone has to make their own decisions however.

Nerd

[docweathers]

I have a 2.5 inch wall thickness skutt KM 1227. Has anyone ever tried wrapping one with high-temperature fiberglass mat?  If not what do you think might happen?

[Mark C.]

When you wrap them the jacket goes pretty fast as the moisture eats up the bands and tightening systems.

I had a friend who wrapped a few old skutts with fiber then with printers sheet aluminum with bands. That still will holden together when the 1st bands fail.

Larry this is job made for your meal skills

[neilestrick]

Yes, you'll just ruin the metal jacket. And you'll be brushing up against the fiberglass every time you get into the kiln, which will be a mess. If you cover the fiberglass with another layer of metal it will compress the fiber and negate a great deal of its insulating ability. If you were going to add insulation to a round kiln, you'd want to use a rigid fiber board. But it's really not worth the hassle. If I had to add insulation to a top loader, I'd put an insulating layer on the lid, since that's where a large percentage of the heat loss happens. With a single zone kiln, however, that could throw things out of whack. The best thing to do is just leave it alone and replace it with a 3" brick kiln when it dies.

[docweathers]

Thanks for the input

 

Leaving alone sounds like the best plan.

[perkolator]

If you're trying to add extra insulation to a 2.5" kiln, my gut says it'd be smarter to invest in some ITC-100 vs the fiber jacket

[StarJupiter]

Does anyone have experience and/or calculations comparing the Cone Art Kiln technology (2.5" firebrick plus 1.0" block insulation) with what appears to be the standard 3.0" firebrick technology used by the other major manufacturers? Advantages? Disadvantages?

 

Cone Art claims a 32% power saving advantage over brick-only designs (comparing 2.5" brick?). Does real-world experience bear that out? Any significant advantage over 3.0" brick kilns? 

 

I suppose the comparisons would be similar regardless of kiln size, but if it does matter, I'd be most interested in the 7 cu. ft. size range of kilns.

 

For example, I would be interested in learning what the differences may be in heating time, maintaining consistent and accurate temperatures, power savings/efficiency, outside kiln heat loss (heating up the kiln skin and surrounding area), kiln maintenance and lifetime, etc.  

 

Many thanks for any input.

 

--Edward

 

 

[glazenerd]

I have a 6.5CF Paragon top loader custom built with 3" brick and 2: fiber: my primary crystalline kiln. I have fired to cone 10 with extended hold ramps ( up to 8 hours). I have been working next to it when it was climbing from 2200 to 2340F: and it was not struggling-at all.

Nerd

[neilestrick]

Does anyone have experience and/or calculations comparing the Cone Art Kiln technology (2.5" firebrick plus 1.0" block insulation) with what appears to be the standard 3.0" firebrick technology used by the other major manufacturers? Advantages? Disadvantages?

 

Cone Art claims a 32% power saving advantage over brick-only designs (comparing 2.5" brick?). Does real-world experience bear that out? Any significant advantage over 3.0" brick kilns? 

 

I suppose the comparisons would be similar regardless of kiln size, but if it does matter, I'd be most interested in the 7 cu. ft. size range of kilns.

 

For example, I would be interested in learning what the differences may be in heating time, maintaining consistent and accurate temperatures, power savings/efficiency, outside kiln heat loss (heating up the kiln skin and surrounding area), kiln maintenance and lifetime, etc.  

 

Many thanks for any input.

 

--Edward

 

We had a big discussion about this here on the forum last year concerning Bailey's double wall kilns. Do a search and you can probably find it. My thoughts on the subject: There is no doubt in my mind that the added insulation will reduce firing costs to some degree. But 32%? I doubt it, and I haven't seen any real world comparisons of actual firing costs to back up their claims. From the information Bailey gave, their numbers were based solely on calculations on paper, not actual tests with loads of pots. If you look at the specs they got from the refractories manufacturer on bricks backed up with fiber board, the heat loss is reduced by 25% . But you can't just translate that number directly to firing costs savings. For starters, that number is based on a static peak temperature, meaning when holding at 2300F, the heat loss is reduced by 25%. It doesn't take into account the energy used in getting the kiln up to that temperature. Nor does heat loss necessarily directly translate into reduced energy costs of the same amount. Second, the fiber board is only in the walls, which only account for about 65% of the total interior surface area. The lid and floor are still just brick, and a greater percentage of heat loss occurs from the lid and floor, especially the lid. Plus you have to remember that their numbers all relate to kilns of 2.5" brick. Compared to 3" brick, ConeArt says the heat loss is only reduced by 20%, which is further reduced by the floor and lid not being double walled. So the numbers are fuzzy at best. There is a lot of anecdotal evidence, but no true side by side tests with work in the kiln, that I have seen. I am happy to recommend the added insulation once I see the tests, because I am all about reduced energy costs, but until then it's just marketing to me. ConeArt doesn't have any specs on their web site that I can find that backs up their claim of 30% savings.

[StarJupiter]

Thanks Neil. Very helpful information - just what I was looking for. 

 

I did search quite a bit for the Bailey double wall discussion you mentioned, but I'm not sure I found the one you were thinking of (the closest I found was from 2013: http://community.ceramicartsdaily.org/topic/4783-thoughts-on-baileys-kilns/?hl=insulation).So, I appreciate the time you took to reiterate the key issues and your thoughts.

 

When I consider the actual cost of firing (based on L&L's example at http://hotkilns.com/what-does-it-cost-electricity-fire-kiln),very roughly it would appear that since the firing of a 7 cu ft kiln is less than $10, the 10-20% savings achieved by the double wall design (vrs 3" brick) would amount to about $1-$2/firing. That's good practical data to use when making a comparison of kiln designs, especially when there are many other factors to consider. I assume, please correct me if I am wrong on this, that when comparing kilns a similarly small percentage difference attributable to the double wall design would apply to other factors such as reaching and maintaining consistent temperature and overall kiln life.

[neilestrick]

Right. The bricks aren't going to last any longer because of the insulation. The relays may last longer than in one of their kilns without the fiber, but relay life can be dramatically different from brand to brand so it's tough to quantify if it's the insulation or the kiln design. Brick replacement can be much more difficult and time consuming with the fiber backing, and I've seen kilns where the fiber board starts to crumble after a few years. I just haven't seen a convincing argument yet for using it.