kiln building

[Mark C.]

There are different types of mortar you can use a commercial one that binds the bricks and will be hard to clean off if you rebuild at a later date. You can make your own mortar and make it friendly so it comes apart easy. I have done both.Thats your choice. Commercial mortars have strong binders in them and the brick will not move.Homemade stuff works but is not as binding.Since your are new and I'm guessing you will reuse these bricks I would make a homemade mix. Firecaly vermiculite or, sawdust, grog , sand,whatever you may want to add.Home made mortar will clean off easy as well.

I'm sorry you had to take it down but in the long run its was the right move. Good for you to see this now.

Just keep asking questions.

you will find homemade mortar reciepes in the books as well.Less water will equal less shrinkage so keep them as stiff(dry as you can) and still work them

 

 

[neilestrick]

It's a good idea to use mortar with hard brick. A mix of fireclay and silica sand is inexpensive and works well.

[Pawelpksa]

Here is how it looks like today.

The most challenging was to move the stensil into the right position without any help. Also cutting the bricks into wedges to finish the arch is extremely hard.

Any comments and guidance to continue?

 

As you could already notice I do faster than thinking (I've got limited time to focus on building) - I made mortar myself. I'm afraid it is a risk factor. I reclaimed clay used for pots (mixture of diffrent clays) and some commercial mortar for owens building plus some grog. I will not know if that mixture takes the heat sufficiently until I try.

What will happen if the mortart does not stand the heat? Will it all collapse?

 

[neilestrick]

If the mortar can't withstand the heat, it will probably melt, resulting in a big mess. If it melts out between the gaps in the arch brick, it could affect the integrity of the arch.

You can cut the hard brick with a masonry disc on a circular saw. It will ruin the saw eventually since the dust is so abrasive. Wear goggles and a good respirator.

[Mark C.]

Fireclay,silica sand-will work just fine.You should check with owens building on if it high temp?if it melts out you wiull wish you had found out about the temp.

(Faster than thinking) slow down and get the details right. 

[Pawelpksa]

35 minutes ago, neilestrick said:

If the mortar can't withstand the heat, it will probably melt, resulting in a big mess. If it melts out between the gaps in the arch brick, it could affect the integrity of the arch.

You can cut the hard brick with a masonry disc on a circular saw. It will ruin the saw eventually since the dust is so abrasive. Wear goggles and a good respirator.

I use various diamond discs for concrete and bricks but my bricks are that hard that I barely go for 1 cm deep and then can use rock hammer. 

You can notice that I used some wood or plastic bars to keep distance between bricks in outer circle. What if I fill the gap (when the distance is taken away) with commercial mortar? Maybe in case the clay mortal melts the commercial one added on top will hold the structure in place? 

[Russ]

Fill in the gap where the key brick is supposed to go? I think even a commercial  castable refractory would start to fail and crumble after just a few firings. Is that what youre asking?

[neilestrick]

For the key you either have to use a commercial refractory castable or bricks. Castable is very expensive. You cannot use mortar as the key.

[Mark C.]

Brick only for the key. They can be cut on a Wet diamond saw-thats your best choice.

The water is key.

You also need to know the melting points of the commercial motar no matter where you use it.

[Pawelpksa]

1) The finishing of the arch is done with the hard brick, no doubts about it. What I wanted to consider is different. See on the following photo - each row of bricks in the arch are positioned in the same distance to the nest row at the top ridge with plastic or wooden stick - they are marked in red. I have to take them off and fill the gaps. I consider filling gaps with commercial mortar which will come stiff and high temperature resistant. In case the clay+grog mortar melts, it shoould keep the arch.

2) Regarding cutting the bricks. In the following picture you can see disc and saw that I use. Should I use water when cutting or you think about different types of disc?

3) Before adding additional layer to the arch, should I lay ceramic blanket on the already existing layer or any other type of isolation?

Thanks in advance.

[Bill Kielb]

Water will extend the life of your blade

[Mark C.]

59 minutes ago, Pawelpksa said:

1) The finishing of the arch is done with the hard brick, no doubts about it. What I wanted to consider is different. See on the following photo - each row of bricks in the arch are positioned in the same distance to the nest row at the top ridge with plastic or wooden stick - they are marked in red. I have to take them off and fill the gaps. I consider filling gaps with commercial mortar which will come stiff and high temperature resistant. In case the clay+grog mortar melts, it shoould keep the arch.

Your clay is what I do not like about your homemade mix as it the weak link-Yes use the comm ercial stuff in that joint that has wood and plastic shims in it.

2) Regarding cutting the bricks. In the following picture you can see disc and saw that I use. Should I use water when cutting or you think about different types of disc?

A small drip of water will help but the main tbing is youir tool/balde is to small to cut 1/2 the brick thinkness. A bigger blade/tool is needed for a clean 1/2 cut.

3) Before adding additional layer to the arch, should I lay ceramic blanket on the already existing layer or any other type of isolation?

What will the enxt layer be??Then I can say about the fiber blanket .

The blanket will only get crushed and will not insulate if a heavy layer is placed on it-put it on top of that last layer if needed -what is the next layer should be the question??If its a layer of homemade insulation add the fiber on top.

Thanks in advance.

 

[Pawelpksa]

I planned to add next layer of hard bricks, unless you suggest to add ceramic blanket and then what... clay?

[Russ]

On my wood fired kiln i have a hard brick arch single row like yours. On top of that I have around 2 to 3 inches of kaowool. Above that is a lower temperature  rockwool insulation. It holds in the heat quite nice. I see no need for doubling up on the hard brick.  its just more mass to heat up. 

[neilestrick]

You don't want to put anything on top of fiber. It will just crush it.

[Rae Reich]

11 hours ago, neilestrick said:

You don't want to put anything on top of fiber. It will just crush it.

I worried about the fiber layers on my catenary kiln being exposed to weather and nest-material-gathering birds (roof but no sides to kiln shed), so I have a "skin" of thin brass sheeting over it. It's self-supporting enough that I haven't noticed crushing over these many years.

Similarly, I made replacement panels to replace the rusted sides of my little converted-from-electric raku kiln from sections of the casings of discarded washers and dryers.

[Mark C.]

I see no reason for two layers of hard brick.I would add lots of fiber (at least 4-6 inches) and  cover that with any material that keeps it dry-Like a metal roof . I put corrugated metal over my fiber to keep it clean and dry and its under a shed metal roof as well.

i do not suggest clay

[Bill Kielb]

I would go for as much fiber as practical without compressing it as the trapped air is a primary reason it insulates. 2 nd layer of brick likely does nothing for you than consume your fuel. If you are reasonably handy with sheet metal, pretty easy to make a removable outer skin for this that protects the fiber and traps more still air. High temp paint (engine block or grill)  could be used for a spiffy finished look.

just some thoughts though

[Pawelpksa]

I have not idea and skils to make the metal shed over the bricks. I plan to put a bit of clay mixed with grog and vermiculite. Then on top of it the ceramic blanket plus some clay to finish. Does it make sense? Thiln itself is well protected from rain with solid roof.

 

[fergusonjeff]

I used a layer of expanded metal with a thin coating of a mortar with additional Portland cement added on top of the fiber.  Has held up really well with little compression of the fiber. 

Try using a cheap circular saw (only $30 new) and 6" masonry disks (about $3).  You can cut almost completely through on one pass.  I have cut hundreds of bricks nd my cheap old saw is still working.

 

[Pawelpksa]

Could you upload some photos? 

[fergusonjeff]

What would you like pictures of?  Kiln?  Saw?  Happy to help, but may take a bit.  I have not posted photos here before.

 

[Pawelpksa]

The photo of the kiln with “metal with a thin coating of mortar”

[fergusonjeff]

The kiln is just a standard catenary arch cross-draft kiln.  the arch is one layer of hardbrick, about 3" of ceramic fiber, and then expanded metal sheets on top.  The thin cement is a mix of fire clay, sand, and Portland cement, but I do not recall the exact mix.  The cement is just thick enough to cover the expanded metal, probably 1/4 to 1/2" thick.  I could try to get a photo, but it is just a solid gray coating - you cannot see the metal.  My shed is 15' high, so it lets rain in at an angle and it has not shown any problems from moisture so far. 

The metal is just "expanded metal" available at any hardware store.  It is commonly used in concrete applications. 

[Pawelpksa]

@fergusonjeff thanks a lot. I looked info Google photos and understood what expanded metal sheet is. In fact I thought about the same as protection for the fiber ceramic blanket. I plan to put thin layer of clay mixed with grog and vermiculite than the blanket, then extended metal and then again clay mix or special cement for owens. 

Open question to all. 

As you can see in my design,  there will be a kind of pedestal in the middle. It can be built from hard bricks. I hesitate from this. Seems to be not very economical - will consume heat and is a waste of bricks as such. Would it be enough to fill the pedestal with some isolation material or leave it empty and put on top a regular kiln shelf?