Making terra cotta bricks

[Peter Angel]

Dear all, i want to carve some bricks while they are soft, then sun dry them,  then fire them extra slowly,  then carve the detail into the well fired brick.

I've researched this and all the instructions tell me to dig up natural clay. I can't do this as i live in the city and i don't have land to dig.

Would it work if i buy some terra cotta powder and silica sand, add water, and mix it thoroughly? 

Regards, Pete

[Tyler Miller]

I would use bagged terracotta sculptural clay which should include grog.

I would also make your bricks a little thinner than conventional store bought bricks.  Commercial bricks are made and fired a little differently, which means they can get away with things we can't.  Have a look at African fired bricks or Roman brickwork for ideas about how to make them in a more potter friendly way.

[tinbucket]

Yes. You might look at some old brick making techniques to give you some ideas. My brother makes wooden molds for custom shapes of bricks, fills them with clay, then wires the excess clay from the top of the mold. The clay he uses is Redart for the color, sand as an aggregate/adds a coarse texture, and some ball clay for plasticity. I fire them to cone 04 and he uses them like regular bricks. The bricks when installed act like a crown molding/baseboard trim. It’s inefficient but it makes his home unique. Adding some type of coarse material will improve the drying properties of clay. Also, I’m not sure why you would add further detail after the clay is fired, it is easier to work with when plastic and holds detail very well.

[Peter Angel]

Triolaz, thanks, do you have the proportions of redart/sand/ball clay that he uses? Pete

 

[glazenerd]

On November 5, 2017 at 7:13 PM, glazenerd said:

* 5-15% grog can be added to either recipe

here is a recipe for standard red brick (cone 04)

50% silica , 25% Hawthorne Bond, 25% a Red Art

and here is a recipe for (cone 04) red body clay

50% Red Art, 15% Hawthorne Bond, 25% OM4, 5% silica! and 10% talc. ( from Alfred U)

 

 

Nerd

[Tyler Miller]

Mod's job, not mine.

[tinbucket]

I think (70) redart, (20) 30-40mesh silica sand, (10) om4 ball clay

[Marcia Selsor]

 

These are from my Architectural ceramics Handouts when I taught Architectural ceramics workshops.  

Marcia

Chip Clauson's Freeze Proof Terra Cotta                                      Batch        % Hawthorne Fire Clay      20       9 C and C Ball                    50        21 Red Art                            100      43 Talc                                   15         6 Muddox Grog                   50        21 .5 Barium Carbonate	Alfred's Terra Cotta Ocmulgee      25% Red Art         25 PBX    Fire Clay  20 Calvert               10 Neph. Syen.        5 Talc                     5 Silica                   10 for handbuilding add 10% fine grog
Terra Cotta    ^06 to ^02 Red Art                100 Gold Art                 40 Ocmulgee               40 Talc                        17 Sand                       12 200 pound + batch  dissolve 3/4 cup of barium carb. on water and add to batch	Carrie Esser Red Sculpture clay  ^04 Goldart           15 Red Art           40 Hawthorne      20 Talc                    5 Neph. Syen.       5 Wollastonite     15 Grog                  20 Barium Carb      1  dissolve first

[Mark C.]

I assume you want to make bricks like this one that a fellow potter made  that says Blue Lake block.

This was fired to cone 10 very slowly

Its a bit more durable than terra cotta  ones

I think what Tyler says-add plenty of course grog at least 20%. Fire very slowly.

The one here is standard size when fired.

The one below it is from Nelson New Zealand-Hand carried it home in the 90s.Xray folks all wanted to see it at every airport.

[Peter Angel]

Dear all,

Thanks for your replies.

I want to make something a bit like this:

 

 

 

[Mark C.]

It may be easier to pull that rabbit from a hat than a brick 

[Peter Angel]

[Peter Angel]

[Babs]

way too long un the sun.

nice work!

[Peter Angel]

These aren't mine!

I think these have been carved after firing.

This is the type of thing I want to make. Pete

 

 

[Min]

Chris Berti's artist statement, " images carved from vintage ceramic brick and drainage pipe" It must be easier to sculpt them out of clay, unless of course you are a stonemason? The lady with the melanoma's looks like you could add a lot of combustable material to the super groggy clay and have it burn out leaving those deep pits and craters. Looks like the female torso is  "Volcanic scoria basalt sculpture" by Jon Dixon, from a google search.

[Babs]

well, some serious grinding and chiselling!

would be less wrist shattering to carve from prefired clay, if the clay was as Min suggests, the variance in colour could be sought by resists in raku type firings

[Sputty]

.
 

[Peter Angel]

We have a similar kind of soft brick in Australia called convict sandstock.

Its a very popular recycled building material and costs the same as brand new brick even though theyre 100+ years old!

Each brick has its own personality. 

[Sputty]

'

[Peter Angel]

Hello all,

I have made a brick mould.

It's made of wood and I keep it wet before adding my clay.

I'm using an ancient roman brick recipe of 60% terracotta powder and 40% fine river sand...(river sand has minimal shell in the sand).

I works really well and the brick mold lifts straight up leaving a perfectly formed brick.  

Here is a you tube video that shows the concept. My mold is less wet than his. I let it drain for a minute. It's closer to damp than wet.

 

The big problem I am having is the wet clay brick sticks to the bottom wooden board.  Even after 3 days it's still stuck.

Any solutions?

Pete

 

[Mark C.]

You have options-you could

Talc powder the board first .

Cover the board with piece of canvas and have a few for when they get to wet.

Use cement board (tile setting substrate-like hardiboard) on bottom board

move to the desert. Barstow is cheap and hot

I can add some other but this is a start

[Min]

57 minutes ago, Peter Angel said:

The big problem I am having is the wet clay brick sticks to the bottom wooden board.  Even after 3 days it's still stuck.

Any solutions?

 

Wire them off with a heavy cut off wire after they have set up a bit.

[Peter Angel]

Thanks for your help.

Mark C, if I use dry canvas, will the bottom of the brick pick up the texture weave of the canvas ?

Pete

 

[Mark C.]

42 minutes ago, Peter Angel said:

Thanks for your help.

Mark C, if I use dry canvas, will the bottom of the brick pick up the texture weave of the canvas ?

Pete

 

Yes -but you can buy slab Matt bless from the manufacture and they leave no texture.