Anyone bought bags of potter#s clay?

[bigegg]

Wierd question, and I suppose I could get the answer by phoning the place I'm buying it from, but...

I'm thinking of buying about 50kgs of high temperature potter's clay to make an experimental wood burner.
I've seen videos on youtube where it is poured out of the bag like sand, but i've only seen it in small (500g) bags where it is "wet".

Does anyone know if potter's clay is supplied dry/powdery or wet/doughy when bought in 10kg/25kg bags?

ta...

 

[mike os]

AFAIK it is usually wet... well clay really

 

[bigegg]

suppose I'll have to delay my plans until 830 when they open...

 

[Wendelspanswick]

suppose I'll have to delay my plans until 830 when they open...

'Slip' or clay can be bought in powder form, but most small users buy it 'wet' as its a bugger to mix the powder/water without machinery.

 

[CompoSimmonite]

Many, many years ago I worked as a lab technician for Royal Doulton and one of my jobs was checking quality of clay when delivered. It was more like a dry soft rock than the sticky stuff you see people playing with on potters wheels It had to be milled then pulverised with water to get to the consistency we required. In the lab I had to made do with mortar and pestle but on the shop floor there was a whole section devoted to turning the "rocks" into clay. We had it runny for pouring into moulds and it was called "slip". Lots of other ingredients were added - not just the ground up and emulsified rock.

 

[pedrobedro]

Are you looking for potters clay or do you want kiln lining which is commonly known as refractory ? That's just an example, you can get it from suppliers online for decent prices or look for somewhere local. There's a place in Dronfield that sells refractory and firebrick in small quantities.

 

[bigegg]

Are you looking for potters clay or do you want kiln lining which is commonly known as refractory ? That's just an example, you can get it from suppliers online for decent prices or look for somewhere local. There's a place in Dronfield that sells refractory and firebrick in small quantities.

It's for a binder for perlite to make a cast insulating shell for the burn chambers - which will be 16" OD/8"ID and 2m long.
The recipe I got is from backyardmetalcasting.com, and is good to 1400C+, which is more than enough for my application, and should only cost me about about 40 quid,including perlite, collected from quite local to me - I already have a largish quantity (2x 25litre buckets) of "grog" (broken firebricks/pottery) which I've crushed to the consistency of sharp sand with my flypress.

I've been researching other materials, such as castable refractory and firebricks etc, but it's difficult and/or expensive to get the correct balance of strength, refractivity(sp?) and insulation in the sizes I need - certainly locally.
This is the best compromise, and should hopefully be good enough for the three year lifespan I need at the moment.

The ease of mixing is the reason I'm looking for dry/powdered clay - it's easy to obtain a decent mixture by starting dry and adding a tiny bit of water at a time.

I'll be making a runny clay "slip" to start with on the inner form of the burn chambers (an 8"ID 0.8?mm sheetmetal tube) to a depth of about 10mm, then placing that in a larger, 1/8" (ish) steel tube (gas cylinder) of 16" diameter and back filling with the perlite/clay/grog mix as insulation.
By the time the sheet metal inner has burnt out (about 4-5 hours at the 1200C maximum temperatures expected in the burn chambers), the clay should have "fired" and be quite hard. The perlite gives the insulation, and the grog provides thermal shock resistance.

 

[bigegg]

Just got off the phone with my supplier (CTM at Doncaster, if anyone is interested).
Turns out it *is* available powdered, specifically for casting, and in stock.

Need to charge my camera batteries, and start a new thread in the "projects" section...

 

[Parm]

Im looking forward to this one

 

[graffian]

Your after fireclay by the sound of it. I can't get it from my local builders merchants but some people seem to have got it from builders merchants.
There is a thread on a pizza oven forum[came up on a fireclay search] about jewsons stocking it.
I will need some in the next few weeks, however I was reading something a few days ago and they used Sodium Silcate as the binder for perlite, seemed it
stands up to higher temp? I think there may be a youtube vid about it, I can't look on this laptop as it has a very stripped xp on it and doesn't play vids.

 

[bigegg]

Fireclay can be had from my local jewsons - *IF* I take a full pallet of 250kgs minimum + £60 delivery!
Can't seem to get it for love nor money in West Yorkshire.
The place i phoned (CTM) said that the powdered stoneware clay they stock is near enough the same stuff - high alumina content.

I wouldn't mind, but about 6 foot down under my garden is a 12" band of pure white fireclay - leeds pottery was only about 2 miles from my house.
Bit of a deep hole to dig tho...

 

[Bobtail4x4]

any building work going on locally?

 

[bigegg]

All just finished ((
And even they don't go deep enough to expose the fireclay.
We're on clay here, but it's red terracotta type - cheap, but not high enough heat resistance.
It melted (turned to runny glass) in my furnace - and that only gets hot enough to melt aluminium (700C), barely copper (1000C), and definitely not cast iron.(1260C)

 

[CompoSimmonite]

Slip clay is poured into plaster of paris moulds, left a few minutes for a layer to have it's moisture absorbed by the mould then the surplus poured out leaving a shell of cup, toilet, sink etc. It isn't normally poured in and left to set. We used to make an earthenware mix that has a thicker consistency with ground up special bricks added. It took a LONG time (week or so) to set in a temperature & humidity controlled environment to avoid shrinkage crack appearing. It was used for commercial sanitary ware - urinals, toilet pans, swimming pool edges, autopsy tables (workers used to eat their lunch off them !) The end result was like a house brick in finish after being fired. I suspect you need to make a stiff mix and press that into the mould for your desired idea.

 

[bigegg]

Your after fireclay by the sound of it. I can't get it from my local builders merchants but some people seem to have got it from builders merchants.
There is a thread on a pizza oven forum[came up on a fireclay search] about jewsons stocking it.
I will need some in the next few weeks, however I was reading something a few days ago and they used Sodium Silcate as the binder for perlite, seemed it
stands up to higher temp? I think there may be a youtube vid about it, I can't look on this laptop as it has a very stripped xp on it and doesn't play vids.

just been reading up on sodium silicate (water glass).
It starts to degrade at 813C - much too low for my application.

 

[bigegg]

Slip clay is poured into plaster of paris moulds, left a few minutes for a layer to have it's moisture absorbed by the mould then the surplus poured out leaving a shell of cup, toilet, sink etc. It isn't normally poured in and left to set. We used to make an earthenware mix that has a thicker consistency with ground up special bricks added. It took a LONG time (week or so) to set in a temperature & humidity controlled environment to avoid shrinkage crack appearing. It was used for commercial sanitary ware - urinals, toilet pans, swimming pool edges, autopsy tables (workers used to eat their lunch off them !) The end result was like a house brick in finish after being fired. I suspect you need to make a stiff mix and press that into the mould for your desired idea.

That's the plan (the "backfilling" I mentioned earlier) - the thin "slip" coating is just a bit of hopefully more durable ceramic to protect the insulation - I may make it with portland cement and a cardboard inner form - the portland will burn out after a couple of fires, but will allow the clay/perlite mix to dry out better than a metal core.