Large quantities of wild clay(water processing very slow)

[TunnleBricks]

Hello, I am digging a tunnel and have thousands upon thousands of pounds of clay. I intend to process it to make bricks. The problem I am facing is how do I process this quantity efficiently? There is a lot of sand and small rocks in it, water processing is slow for this quantity. I am unsure if this is the right place to be asking about this but I am at a loss. Any help is appreciated!

[Denice]

What type of bricks are you wanting to make?    Some type of bricks you will find  gravel size rocks in it,   you probably just add some ball clay to it to adjust for the sand.   How do you plan to fire them?  Have you  tested it and see how it holds together?    Denice

[Callie Beller Diesel]

If you’re digging your own clay, you have to do a bunch of testing to figure out its properties first. If you want to process it efficiently you’ll need some kind of mixing equipment, whether it’s a pugmill or something like a Soldner mixer. If you’re doing it as a one-off project, there’s going to be nothing efficient about it, and I suggest just enjoying the process. If you’re looking to do a bunch of similar projects, it’s one of those things where you have to do a lot of testing and setup that will lead to efficiencies of scale. 

I don’t know that I’ve heard of anyone slurry mixing brick clay. I’ve seen youtube videos of some low tech brick making operations in places like India. They start with a clay that would be far too wet to throw or handbuild with, but isn’t quite wet enough to be reclaim either. They didn’t show the clay prep, so I don’t know if there was a mixing or sieving process involved, or if the material was used as-is. They loaded it into a wooden mould that was open on top and bottom, so they formed the bricks in the place where they’d be left to dry. 

[PeterH]

Appendix 3 of Michael Cardew's Pioneer Potter contains a few pages on brick making with minimal facilities.

Apparently simple bricks are made by slop-moulding using the sort of open frame Callie mentioned, although multi-brick moulds can speed things up. He suggests the slower stock-molding is used for special bricks (end-arches, side-arches,springers, bull-noses, flats, etc).

The bricks are fired in a clamp, and the outer layer(s) of bricks are apparently discarded after firing.
45,000 bricks give a clamp about 30ft long, 15ft wide and 12ft high - with about 5,000 (12%) of the bricks discarded.
4,000-5,000 bricks gives a clamp about 10ft by 10ft by 8ft6in - with about 40% of the bricks discarded.

He discusses a clamp for about 25,000 bricks with 10 fireplaces, and suggests that at least three-quarters of a cord of wood per 1,000 bricks are needed. It seems with care you can fire for 48hrs before you need to draw the embers. The firing is apparently finished when the top course of bricks glows red. I've no idea how long a total firing takes.

PS IIRC elsewhere he discusses a bootstrap process if you want to use the bricks to make a kiln. First make a "sacrificial" kiln of  clamp-fired bricks,  and then fire another load of bricks in this kiln to a higher temperature for use in "real" kiln-building. (Assuming your cay is suitable.)

Edited May 25, 2023 by PeterH

[TunnleBricks]

@Callie Beller Diesel I am looking to make bricks for a house. I'll have enough material to make several thousand bricks. My concern, based off lack of knowledge and use of clay is that I will fire the bricks and they will break apart. If I could use the clay as is that would be fantastic! I watched a video of Indian brick yard and their clay seemed processed in a way that wasn't explained. Im in western washington so sun drying wet clay isn't a problem. Also it's really  fun to work with clay!

[glazenerd]

12 hours ago, TunnleBricks said:

Hello, I am digging a tunnel and have thousands upon thousands of pounds of clay. I intend to process it to make bricks. The problem I am facing is how do I process this quantity efficiently? There is a lot of sand and small rocks in it, water processing is slow for this quantity. I am unsure if this is the right place to be asking about this but I am at a loss. Any help is appreciated!

To start, make a small tile by hand (nothing fancy) and let it dry> did it crack while drying? Next fire it to cone 06? what color? did it crack? The first step in wild clay processing is to see if its worth working with. Get past the simple test. Next, dry process 1 pound by pulverizing chunks into powder. Work it through a strainer ( window screen, kitchen strainer, etc) and repeat the above process to check how it dries and how it fires. >>outside with a mask<< How much sand? After you dry process one pound; put a 1/4 cup of dry clay in 3/4 cup of water in a clear glass container, and stir/shake well.. The sand will settle out very quickly. The thicker the sediment layer on the bottom equals the amount of sand present. 15-20% sand is acceptable, alot of brick makers add and for malleability. Commonly called temper in the wild clay circles. Run these simple tests and get back to me once you have. 

Note: worked with two potteries in India that used subtropical laterite clay. After the monsoon season; laterite can be found in smaller streams up to 4-5 feet thick. They simply dig it out and put it into brick molds. Sub-tropical laterite is the most common clay in India with over 40% combined alumina/.iron content. It dries so hard that it is often not fired before using as a brick. A property known as cementing occurs that makes unfired brick almost as hard as fired brick in the States. 

Tom

 

[Callie Beller Diesel]

22 hours ago, TunnleBricks said:

If I could use the clay as is that would be fantastic

This part here is not going to happen. All clay is not the same. You will likely have to process it somehow, and it will need to be fired. I haven’t checked the geological survey to confirm, but I’m pretty sure Washington state doesn’t have sub-tropical laterite, and if it did, there’s still a freeze thaw cycle to consider. 

In order to meet building code, you’d have to do a LOT of testing and work out a making process to make sure those bricks aren’t going to be a hazard to the finished building or to the humans who live in it. 

The scope of making an entire house worth of bricks is huge. In terms of labour and expense, it’s going to be the least cost effective thing you’ve ever done.  I’m not saying that to discourage you if you’re set on the path, just trying to make sure we’re working from the same set of base assumptions. All of us here absolutely understand the joy of working in clay and how absolutely compelling it is to work with. If your heart is set on doing this, start with the initial tests suggested by glazenerd. 

[PeterH]

23 hours ago, TunnleBricks said:

 I am looking to make bricks for a house.

My uncle built his own house, so I'm fully aware that it's doable. However have you checked to see if the use of home-made bricks might interact with such things as:

- Planning and building regulations.

- House insurance.

- Resale; e.g. is there any impact on the buyer obtaining a mortgage.

[Kelly in AK]

There was a brick plant in Anchorage in the 1950s, briefly. They used clay straight from the ground and ran it through a large pug mill. Fired them clamp style. The working and firing properties of the clay were known, and lots of testing for structural integrity and freeze/thaw resistance were done.

The engineering tests of finished bricks will be critical if you’re using them for a structure.

You’ve got some work to do well before figuring out how to make them en masse. See if you can make a couple dozen to completion, that will give you a lot of useful information.

The Cardew reference is excellent. 

[Babs]

Lots of mudbrick building and afobe in the 60's

Maybe some of those books etc still around, unfired mostly.

What's the climate in your area?

[PeterH]

11 hours ago, Babs said:

Lots of mudbrick building and afobe in the 60'

+1

Would a local historical society know about such buildings in your locality? It's where we found out about some of the older/more-unusual buildings in my area (Essex).

Just the 1st background reading I found, so no claims about its quality.

How to make mud bricks, and why you might want to
https://www.heifer.org/blog/how-to-make-mud-bricks-and-why-you-might-want-to.html

Mud brick
https://www.yourhome.gov.au/materials/mud-brick
... note the mention of cement-stabilised soil bricks

[Russ]

Adobe is easy to make provided you have sand and straw and is quite stable. Typical size is 10x14x4. Needs to be plastered with a cement based product just for weather protection. Been used for thousands of years here in the southwest. I work with it quite frequently in Santa Fe. Probably your best bet for what you have. A wooden form is easy to use and make to form the adobe.

[Callie Beller Diesel]

Adobe is great in the desert, but notsomuch  where we get more freeze/thaw cycles. In college it was a fun intro first year project to make adobe sculptures in the courtyard as a group out of some reclaim and straw. They’d be left in place and by spring they’d be pretty disintegrated.

[Babs]

2 hours ago, Callie Beller Diesel said:

Adobe is great in the desert, but notsomuch  where we get more freeze/thaw cycles. In college it was a fun intro first year project to make adobe sculptures in the courtyard as a group out of some reclaim and straw. They’d be left in place and by spring they’d be pretty disintegrated.

Can use a sealer end product and protect under wide verandahs...great lesson to learn re clay though, Callie.

Folk here @glazenerd added laterite rubble to the clay mix!

[Kelly in AK]

One more thing, bricks are not pots. Stuff that would disqualify a clay for pottery may not for bricks. You’re looking for enough clay to hold it together, and it to stay together until it’s fired. Additions of fibrous material are common to brick making. Critical for adobe blocks. Aggregates much too large for pottery clay are also  common in brick clay. Plasticity is a wholly different issue for potters than brick makers. Your first tasks:

1. Can it be formed into a brick?
2. What are its fired characteristics at various cones? 

[glazenerd]

5 hours ago, Kelly in AK said:

One more thing, bricks are not pots. Stuff that would disqualify a clay for pottery may not for bricks. You’re looking for enough clay to hold it together, and it to stay together until it’s fired. Additions of fibrous material are common to brick making. Critical for adobe blocks. Aggregates much too large for pottery clay are also  common in brick clay. Plasticity is a wholly different issue for potters than brick makers. Your first tasks:

1. Can it be formed into a brick?
2. What are its fired characteristics at various cones? 

Well said. Brick making relies on malleability, not plasticity. Seen a few million bricks in my 50 year carpenter career, and pending the clay mine; chunks up to 3/8” is not uncommon. Potters avoid black coring, whereas the brick industry utilizes it to produce low absorption. Brick is fired in the 06-04 range mostly, at a fairly high speed with the intent to produce black glass (coring). It all comes down to the original poster willing to do that much work. Just so you know; 7 standard size bricks equal 1 square foot. 

Tom

[Russ]

19 hours ago, Callie Beller Diesel said:

Adobe is great in the desert, but notsomuch  where we get more freeze/thaw cycles.

We have plenty of freeze thaw cycles here in the high "desert". ..About 5 months worth yearly. Hence the cement plaster! But there are still high end homes  that are adobe and mud plastered. Its an aesthetic that some love and are ok with an annual coat of mud to keep it natural.

Once plastered the adobe will last for many years... ie; Taos Pueblo which has been around for about 950yrs... and they only use mud plaster.

Oh and there is stabilized adobe which has an asphalt product mixed in... the same stuff that is painted on below grade cinder block.