Hi answerpoolians!
I,m working on a kind of block that is lightweight and is resitant to fire.
when it reaches 1200 c(the degree for making the block) it starts to puff a little.
How can I prevent the block from puffing?
I dont want to use any mold in the furnace because it will make it expensive.
Any solutions?
Thanks

Welcome to our pool. I hope we can be of help.

You have a question now I have a question.

What material is the block made of?
What is it's shape? Round, ,sphere, square, rectangle or other.
What size is the block?
Is it solid or is it hollow?
And lastly, can you explane "puffing" a little?

All these will help some to be able answer your question.

What I am actually thinking is that you have a rectangular block, A rectangle will have less material at the corners and ends than in the middle - So instead of swelling you are experiencing uneven shrinking. It does not bake in the kiln evenly - the outer ends will "bake" faster than the center portion.

Fire bricks are combination of clay (fireclay) granulated (ground) fire brick (grog) which will shrink a great deal more than plain clay. I'm assuming your mix is around 70% fire clay and 30% grog. Some others have other minerals/metal oxides added for different properties,

Fire bricks are a bit more porous than solid clay bricks. IF the material you are working with is not as porous, that may be the problem.

Many of the fire bricks that are rectangular in shape come with a stamp in the middle/top which actually reduces the amount of material in that area. If your brick is "swelling" (actually not shrinking as much) in that point, then you could do similar by cutting a dent/rut/divot out of that area. I note that fire brick comes in "paver" flatish shapes without missing mass (stamp, gouge, v shaped indents at top and sometime bottom of the brick) - the thinner the brick, the more even the bake.

I would suggest a few firings of different shaped bricks - where your "puffing" is taking place reduce the amount of green brick (wet) it may take a few times to fine tune the amount of material you need at different points along the length of your brick before you find the one uneven rectangle that fires into "true" rectangular form.

I'm guessing that your "puff" is not to large thus only a small amount of material needs to be removed from the wet brick to get an even finished product.

I'm going to assume that you do have a mold to make your standard block shape and size and my pressing in the clay into that and pressing you are shaping your block. IF it is a wood box, you might want to add a bit of lathing strip, about the width and thickness of a paint stir stick, adhere that to the bottom of your mold getting your "dent" in the center/middle of the bottom of your brick, thus you can roll out or press flat at the top.

quote:

Originally posted by Walks On Water:
Welcome to our pool. I hope we can be of help.

You have a question now I have a question.

What material is the block made of?
What is it's shape? Round, ,sphere, square, rectangle or other.
What size is the block?
Is it solid or is it hollow?
And lastly, can you explane "puffing" a little?

All these will help some to be able answer your question.

Hi Walks on Water & DvdGStwrt
Thank you for your reply on my topic
It seems that this pool is very active and I,m happy for that
my english is not so good so sorry for my mistakes
Well about the puffin stuff!
Its made of a kind of illite that will puff when it reaches near 1200c
I think its density is near 1200 kg/m3 (i,m not sure but i guess its near that....we are working on the tests so we can have precise tests)
It has a very good resistance to pressure and tension but the exact results will be found soon.
we are trying to produce blocks that are like 8x8x16 inch size.This is not the problem.Wefear that we cant mold the fireclay and then the puff ruins our work.
Anyway it becomes a little bigger but we want to prevent any risk.

"I'm guessing that your "puff" is not to large thus only a small amount of material needs to be removed from the wet brick to get an even finished product."
I agree with you dear DvdGStwrt.You really helpt me.It seems that your an expert!
I hope I can get some good advices from you when i,m trying to make the block coming out!!
Thanks
and peace