Making clay 101

[Marcia Selsor]

I was a caretaker of a religious estate in Upstate NY. I also had a studio. from an abandoned greenhouse on the estate, I gathered up about 50 earthenware clay flower pots.

I would mix a trash can of slip, lined the flower pots with cheese cloth and a little piece of paper over the hole and put slip into the pots. I had them lined up on shelves in the basement of the mansion I where I was care taking.This made very nice throwing clay after a day or so.

it was an inexpensive way to make clay without mixers and pluggers.

Marcia

[Marcia Selsor]

I thought I might mention that making a slip first and letting it dry to usable consistency creates a very plastic clay body through that process.

It was used around the Mediterranean for millennia. So regardless of whatever recipe you are using, this is a great simple way to mix. You can also dry out the slip i other material: on plaster or concrete slabs, in various clothes like tied off jeans, pillow cases, etc.

 

As for a darker color, reduction firing would do that. Otherwise you may have to resort to something containing manganese which is not safe.

 

 

Marcia

[AtomicAxe]

huh. Never thought about flower pots ... that is definitely an interesting way to go.

 

you could even sew a .... bag ...... perhaps for the inside out of canvas so it is a little more contained.

 

As for the slurry method, I don't see problems with it. Just like everything else it's all in the details, use some sort of electric mixer to get a good pre-blend when it's slaked and go to town.

 

As for drying ... depends on the conditions. Where I'm at now, I will pour onto canvas that is sitting on a plaster bat inside then wrap the top so it's like a clay burrito ... 3 day later I wedge. If I need it today, I will still wrap like a burrito, but that clay is sitting in the sun on a big slab of concrete. It's about controlling moisture loss at that point without making it too dry in some parts, but not dry enough in others.

[Biglou13]

thanks for all the info big help

 

i have these high tech air pot/ rootmaker pots that have holes on all surfaces, and will work perfect with pillow case

 

when making clay in mixer ive read its approx 4 parts water to 1 part clay, (weight)

?for slurry or slake mixing what ratio water to clay?

granted too much water will correct it self in drying, im trying to calculate ball park for mixing in 5 gal buckets

? is 70-140 screen silica ok for clay body? (im told its actually finer but has occasional large particle)

im trying to make a clay body from local material and that is what is available locally.

 

silica (http://digitalfire.com/4sight/education/formulating_a_porcelain_282.html)

 

"Silica Silica tends to be a very consistent and inexpensive material. Quartz grains act primarily as a micro-aggregate or framework structure for the fired matrix. In addition, some of the silica is dissolved by the fluxes to produce aluminum-silicate glasses. Too much silica in a recipe could mean lower plasticity (since less room is left for clay). However, there is also much discussion about the detrimental effects of crystobalite (i.e. dunting), whose development during high temperature firing is related to available free quartz. Thus there is some merit to lower silica amounts, especially if you have the ability to adjust your glazes to lower their expansion. The use of less silica means more clay can be added resulting in higher plasticity. A finer silica (300 mesh) reacts better with the fluxes and thus less is needed. Too little silica in a body can mean crazing glazes since the quartz mineral contributes to the low expansion that assists glaze fit. For cone 10, many technicians aim at 20-25% for expansion reasons and to provide firing stability over a range of temperatures"

 

 

 

ill be mixing an epk based clay body, occasional wood firing, or whatever kiln i can get in (with testing of course)

from

http://www.anagama-w...clay_bodies.php

 

Slightly Modified Lehman D12

EPK 36.80

Nepheline Syenite 24.50

OM4 Ball Clay14.30

Silica19.10

Bentonite5.10

Redart2.50

Sum102.30

This slightly Modified Lehman 12-D is derived from the recipie contained in Dick Lehman's article A New Approach To Long-Fire Results

[AtomicAxe]

?for slurry or slake mixing what ratio water to clay?

granted too much water will correct it self in drying, im trying to calculate ball park for mixing in 5 gal buckets

? is 70-140 screen silica ok for clay body? (im told its actually finer but has occasional large particle)

im trying to make a clay body from local material and that is what is available locally.

 

 

Slightly Modified Lehman D12

EPK 36.80

Nepheline Syenite 24.50

OM4 Ball Clay14.30

Silica19.10

Bentonite5.10

Redart2.50

Sum102.30

This slightly Modified Lehman 12-D is derived from the recipie contained in Dick Lehman's article A New Approach To Long-Fire Results

 

We'll start with the clay body recipe, just remember that redart is different from lizella. So test and modify accordingly especially when that clay body is using it for color not for a main ingredient.

 

as for the ratio ... I don't really know sadly ... I just have a big bucket of dry mix I make that is blended roughly , then just add to a bucket of water like plaster until it doesn't take any more, then add a little more and blend like a bad mofo. when it's all slaked from my dry mix .. how ever many buckets that is ... I will pour onto my canvas all at once and that is my slaking process.

 

for a red clay, that mesh of silica is fine. The extra iron in the clay will help it bind, though I prefer true 200 mesh.

[Biglou13]

If my supplier only has 320 screen silica vs 200, Will that cause a problem?

[Biglou13]

http://www.anagama-w...clay_bodies.php

 

Slightly Modified Lehman D12

EPK 36.80

Nepheline Syenite 24.50

OM4 Ball Clay14.30

Silica19.10

Bentonite5.10

Redart2.50

Sum102.30

This slightly Modified Lehman 12-D is derived from the recipie contained in Dick Lehman's article A New Approach To Long-Fire Results

 

ok im going to make this, using slurry method,  drill paint mixer.......tomorrow.

do i need to mix in any specfic order?

any special handling for bentonite?

[Biglou13]

small disaster 

 

after reading how "sticky"bentonite is i blunged my bentonite with hot water, using a hand held mixer,  night before.

i started with 10%, 10# of recipe

ive read 4:1  is normal ratio  h20 : dry

 and vaguely recall 6:1  for slurry technique

i estimated appox 7:1   for a loose mix (not to burn up drill)

water is approx 8 pounds/gal

so for 10#   dry approx 40# water or approx 5 gal

i opted for approx 7 gal

 

 

way too much water!!!!!!!

i kept adding dry ingredients in (.05 x100) increments of recipe   until i ran out of one ingredient.

well at best its a little thicker than glaze consistiency.

starting ratios are way off  im at aprox 0.6:1  dry to h2o   (barring any mistakes along the way)

 

All is not lost, i hope

its aging..... settling..  on porch now.... will decant clear water off in next day or 2.

 

note:  after assembling all ingredients and equipment  it wasn's as much a P.I.T.A.  as many have implied. internet taught me much bentonite for detox

 

......live and learn......

[Min]

When I tried mixing a claybody with bentonite I dry blended it into the other ingredients then added the mixed dry clay to water. I did use a mixer/pugger so maybe this way wouldn't work with the slurry method but I don't see why not. One of the commercial bodies I use I bought in 50 lbs sacks of dry, pretty sure it contained bentonite not macaloid, I mixed that with water the same way. 

 

I noticed your recipe has a fair bit of nepsy in it, slightly soluble, any problems with decanting too much water do you think? I was wondering if you should mix up a small batch of your clay recipe dry and add it to your really wet mix instead of decanting, just a thought.

 

Min

[Biglou13]

i kept adding more dry mix until i ran out of one of the ingredients  silica. i wont be able to mix more until i can make it to supply house, next week

 

are you saying nepSy goes into solution with water and wont settle out/down?

 

how do you mix yours,  how much water to dry?

[Min]

i kept adding more dry mix until i ran out of one of the ingredients  silica. i wont be able to mix more until i can make it to supply house, next week

 

are you saying nepSy goes into solution with water and wont settle out/down?

 

how do you mix yours,  how much water to dry?

 

No, what I meant was nepsy is slightly water soluble, some of the minerals will be in the water. Therefore if you decant a fair amount of water you will be throwing a bit out, soda, in this case. I don't know if it would be significant or not.

 

Moist clay is usually about 30 to 70 ratio of water to clay.

 

I mixed in my mixer / pugger (Bailey has one that is actually a mixer / pugger combination, not just a pugger like some)

 

Min

[Biglou13]

Yeah my ratio was way off found my notes too late. Starts with 4:1. Dry to h20......(Dumas) oh well

 

Well I've read that the flux nature with the silica will be greater due small slica size.(I used smaller mesh).... But with the way it's I'll be slightly over fluxed.. Hope the nep Sy loss won't be to great

[oldlady]

just checking.......... i replied to your question about order of ingredients and bentonite. it does not appear here. wonder what is going on?

[Biglou13]

Glitch

 

can u repost or pm me please

[Marcia Selsor]

there may be. Check the brand label. Mixing your clay using some store bought material is still cheaper than buying moist clay which is 30% water. But consider you want to go to cone six. It could be really difficult to dig clay that matures at that temperature. Listen to Atomic who offers a clay body with two of your local ingredients plus commercial clays to get you what you need.
I mixed a nice cone six stoneware for many years but not with Lizella. You need the right ingredients. If you want to dig lay and be natural, work with earthenware like Lizella that will mature about Cone 04 to 1maybe.

marcia

[Biglou13]

ok round 2

 

i used soup from round 1 as liquid and made more clay

 

i started with all dry material in bucket approx 20# dry material added about a gallon of the soup...to thich.....added approx 2 more quarts mixing with drill mounted paint stirrer. got a point of loose mud but had cottage cheese size lumps, added alittle more soup and continued to mix until there were barely any lumps left. poured mix into 2 pillow cases which are inside 2 rootmaker flower pots, drying

 

much better attempt than 1st try!!!!!

 

ill post images when dry enough to wedge.

 

old lady can you pm me or repost order of mixing........

[oldlady]

sorry, i just found this and did not know you were asking for something from me.

 

there really is no order for mixing ingredients, just be sure that you mix some of the  dry ingredients in a dry container and add the dry bentonite and stir it in well before adding any water.  bentonite turns into a gel when it gets wet.  make sure you mix it well into other things so it does not sit in a clump. wear a respirator so you do not breathe anything in that mix. 

 

when i make glazes, i put the things into order by amount of ingredient from small to large.  this is because i have an old Ohaus scale with weights that hang on the end of the bar once you measure more than what the slides will handle.  i have 500 and 1000 gram weights.  more than once, before i realized what i was doing, i would weigh something like 800 grams of an ingredient and mark that finished.  then i would forget that the 500 gram weight was still on the scale and try to weigh 350 grams and actually wind up with 850 of that second ingredient. that is ok if you eventually notice what happened before finishing the recipe.(and if you can do the math to alter the amount of everything else to fit the error!)

 

if you are buying equipment these days, i understand that digital scales are reasonably inexpensive and accurate so you do not have to alter the order of the ingredients by amount. 

 

hope this answers your question.  sometimes your very spare way of asking things confuses this old head.

[Biglou13]

I'm a little confused about silica(quartz,flint). I've read where some use it as grit, other times its the"glass" in a mix be it clay or glaze.

 

I understand there needs to be a flux present to melt it.

when is silica grit/grog? when is it a "glass" maker and melts?

Is this a situation where size does matter?

 

I have a silica sand . the screen size is 140. Sure prolly to big for glaze,

but is it to big to be used a silica component when making clay?

 

I got some large by product from sand mining, quartz "pebbles" Much as large. As 1/4 inch. I'm told its mostly quartz, ocassional clay pebble, tiny sharks teeth, and even fools gold (iron pyrite). How would this holdup as inclusions in clay?? currently firing to cone 6 ox, but will eventually be used in wood fired also. (Yes of course I'm testing soon)

[Biglou13]

Good question big.....

 

Here is some insight.

 

"The term 'silica' can be misleading. It is important to understand the difference between 'silica mineral', 'silicates', and 'silica glass'."

......... http://digitalfire.com/4sight/material/silica_1245.html

 

Quartz also Sio2

 

"Unlike silica glass, the quartz phase of silica is subject to inversion and accompanying volume and form change when fired through 573C. Room temperature quartz is called alpha quartz, beta quartz exists only above 573C.

 

Quartz sand is often used in bodies as grog for texture and to increase thermal expansion. Powdered quartz is used in glazes and bodies also. Quartz of very fine particle size (-400 mesh) will typically enter the feldspathic melt or convert to cristobalite during firing if fluxes are lacking, coarse powdered grades help to 'squeeze' glazes into fit. Intermediate sizes (200-300 mesh) seem to be best however, since their greater surface area exerts more compressive squeeze per unit.".....

- http://digitalfire.com/4sight/material/quartz_1171.html

 

Flint yet another. SIO2. Silica...

"A metamorphic rock high-silica content stone sometimes referred to as pottery quartz or potter's sand. Once calcined to 600C flint-stone can be easily crushed to powdered crystals. As with cristobalite, substituting quartz with flint can avoid the quartz-splitting syndrome.

 

Flint is usually contaminated with limestone (thus the CaO content and the LOI). There will also be trace amounts of iron and MgO. European glaze recipes often call for flint. It is typical to simply substitute quartz."

 

http://digitalfire.com/4sight/material/flint_316.html

 

 

Ps. The clay I made in earlier post was just wedged, It was still a little moist. But it's clay nonetheless!!!! Can't wait to thow and build. With it.

[Biglou13]

When making a clay body, will using 120 screen silica vs 200 make a difference?

 

How about 300 screen silica?

[Guest JBaymore]

The larger the particles of material, the slower they become involved in any melting.  So the answer also ties into firing cycles and the objectives of the material.  Are you using this to get glassy phase developed in the body?  If so, the larger particles will delay their involvement in a melt with the active fluxes present.

 

best,

 

.............john

[Biglou13]

The latest recipe is a slightly modified slightly modified lehman 12-d body. See above post.. I changed red art for lizella, and used percentage of 140 and 325 silica. And decreased bentonite. (Drying slurry)

 

This first test 2 small yunomi just got finished In a 3 day wood firing. (Original recipe) I need to go pick them up.

Is a three day firing long enough if its held at the higher temps for a period of time. To,get the flux (nepsy)to glassify the silica? Along with ash deposits.

 

Also digital fire alluded to the point that smaller particle used less flux. Will the inverse apply more flux will balance the larger silica particle?

 

I really need to get a ceramics chemistry text book at this point any suggestions?

 

Sensei john and others , Again thanks for the help.

[Guest JBaymore]

I really need to get a ceramics chemistry text book at this point any suggestions?

 

"The Magic of Fire" book that comes with the Level II version of Insight glaze calc software.  Plus the online tutorials that teach you how to use Insight.  Plus having Insight (free time limited download) and learing what iot does and how to use it.  And a copy of the latest (last) version of Daniel Rhodes "Clay and Galzes for the Potter" updated by Robin Hopper (which is out of print and now expensive... but a GREAT intro book).

 

best,

 

................john

[Biglou13]

Rhodes book ordered.

 

Other when get off I pad.

[Biglou13]

ok i have a new clay drying technique....

i use the slurry method..... then dry the clay in pillow cases in  rootmaker flower pots.

 

i took one pillow case full and put it on top of grate of air conditioning condenser, 

 

i got a few  weeks of drying in a day.