“Ball Clay”-Processing, Properties, Uses & Formula

Ball Clay– What is it?, Properties, Chemical formula & Composition, Test, Mining & Processing, Uses, Suppliers & everything you need to know about Ball clays.

What is Ball clay?

Ball clays are kaolinite rich secondary clay which is available in dark brown to black colour due to relatively high organic impurity content. Once it fired, it will become white to lite cream colour. It consists of three major minerals that are kaolinite, mica & quartz. It is a high plastic clay and contains more fine particles. It is also known as plastic clay. The name ball clay came from the mining method of cutting the mud out in balls. Many properties match stoneware clays, but these stonewares never gives white product after burning.

Ball clays are characterised by higher plasticity, dry shrinkage and dry strength as compared to china clays. They are chemically impure and often contain a large proportion of silica, iron and titanium impurities.

The sedimentary clay also contains both carbonaceous matter and lignite in the agglomerate form (>50Mic) and colloidal form(<2 Mic). It’s believed that the carbonaceous material within the prescribed limit (<2wt %) influences the physical properties of the clay and also increases the unfired strength of clays. However, it increases porosity after firing, resulting in a decrease in fired strength. It also increases the casting thickness.

 

Ball clay Properties:

The ball clay deposit is sedimentary and consists of numerous strata which frequently vary significantly in physical properties although perhaps not much in chemical composition. Ball Clay is genrally called Kaolin, that had been transported from the primary decomposed parent, or igneous rock which were usually granite by nature via glacial displacement making It is a secondary clay, and in this process, it not only does it gain high organic impurities and iron contaminants but the material gets ground down into a finer particle size! Quality specifications of ball clay: Some relevant quality specifications of the ball and plastic clays are:

• Residue/girt content on 45 microns (325 mesh) IS sieve should not be more than 2.0 wt%
• Particles coarser than 25 microns should be~ 3.0 wt%
• Particles fine than 2 microns should be~70 wt% Min
• The water plasticity should be ~ 34 wt % Min
• Unfired Strength (MOR) should not be less than 35.0 kg cm2.
• Contents of Fe2o3 & TiO2 combined should not exceed 2.75 wt%, and the individual constituents should not be more than 1.5 wt%

 

Physical properties of Ball clay:

Main features include high plasticity due to fine particles which give high green strength for handling the product at the green stage. Requires much more deflocculant to get required fluidity compared to china clay because of fine particles and organic impurities. High Green MOR compared to china clay due to more fine particles. Fired shrinkage is comparatively more due to high loss on ignition and particle size distribution. Green Modulus of Rupture: 65 Kg/cm².

1. Water absorption after Firing: Around 10%
2. Ph value: From 6 to 8.
3. % of Dry Shrinkage : 3 to 4 %.
4. % of fired shrinkage: 4% to 6%.
5. Residue on 40 mesh : 1% to 3%.
6. Casting rate is comparatively low when compared to china clay in slip condition with same fluidity, viscosity and density.
7. Drying time is slow compared to china clay.
8. Ball clay should never tested for colour in the concentrated state since its density, and adsorbed salts give colour intensities which are misleading.

Chemical Formula & Composition of Ball clay:

The Chemical formula of ball clay is Al₂O₃. 2SiO₂.2H₂O.

The chemical composition of ball clay varies very much from place to place even from one lot to another.

Mineral	Percentage
SiO2	45% to 55%
Al2O3	30% to 40 %
MgO	0.1% to 0.5%
TiO2	0.5% to 2%
Fe2O3	0.50% to 1.5%
Cao	0.1% to 0.5%
Na2O	0.1% to 0.6%
Loss of Ignition	Around 14%

Ball clay Processing:

Ball clays are sold directly from the mine without processing, other than the air-drying which may occur under favourable circumstances.

 

Ball clay storage for use But some cases Ball clay proceeded after mining before packing to remove impurities. Steps in the Ball clay processing are

 

• Mining.
• Sieving.
• Settling.
• Fitter pressing.
• Drying.
• Packing.

Mining:

Ball clay is extracted generally by a mechanical, hydraulic backhoe. Then it will be mixed with water and sent to sieve.

Sieving:

Then the ball clay slurry is passed through a series of sieves to remove the impurities. This sieve is passed up to 40 mesh.

Settling:

After sieving the slurry will be passed through a series of zig zak settling to allow clay particles to settle down. In this stage, the maximum amount of water will be remove.

Filter Pressing:

The slurry from the settled tank will be feed into the filter press to remove the water to form cake state clay.

Drying & packing:

The cake form ball clay dried in the atmosphere for some time. Then it is packed in 50 kgs bags and transported to the customer.

Normally Single ball clay is not used in the process because of much varying properties from one delivery to another delivery. So normally two or more ball clay is mixed and used in production process in sanitaryware.

 

Ball Clay Tests:

Following are some of the test that is carried out in a laboratory where ball clay used as a raw material in the production process. Sample for testing will be taken from different areas from the clay leap so that the result will be accurate.

 

1. Moisture Test.
2. Alkali Demand Test.
3. Residue Test.
4. Shrinkage test.
5. LOI Test.
6. Water Absorption Test.
7. MOR Test.
8. Casting Rate.

 

Moisture Test:

This test is carried to find out the percentage of moisture content present in the received ball clay load supply. Formulas for Percentage of Moisture is

Moisture % = ((W1 – W2)/W1)*100.

Where W1 is initial weight (100 gm),

W2 is Final weight after the sample was dried.

Alkali Demand Test. This test is carried out to find the Sodium Silicate solution required to obtain less than 20 this for ball clay slip. The formula used to calculate the alkali demand is,

Alkali Demand % = ((Z/2)/W1)*100 ,

whereas Z is grams of sodium silicate solution added & W1 is the weight of the clay taken initially.

Residue Test:

This test is carried out to find the residue percentage in the clay on 200 mesh sieve. The formula used to calculate the % of residue in clay

Residue % = W1/{((Density x 100) – 100 x 1.625)} x 100 ,

whereas W1 is weight of residue.

Shrinkage Test: This test is carried out to find the Dried shrinkage %, Fired shrinkage % & Total shrinkage % for ball clay.

The formula used to find the Dried Shrinkage is,

Dried Shrinkage % = (L1-L2)/L1 x 100.

The formula used to find the friend shrinkage is.

Fired shrinkage % = (L2-L3)/L3 x 100.

The formula used to find the Total shrinkage is,

Total shrinkage % = Dried shrinkage % + Fried shrinkage %

whereas L1 is the initial length of the casted sample bar,

L2 is the length of dried sample bar after drier,

L3 is the length of the fired sample after kiln.

LOI Test:

This test is used to find the loss of ignition of the clay. Weight loss during firing is called the loss of ignition. The formula used to find the LOI is,

LOI % = (W1-W2)/W1 x 100,

Whereas W1 is the initial weight of the sample taken,

W2 is the weight of the sample after firing from the kiln.

Water Absorption Test: Formula used to find the water absorption percentage is

Water absorption % = x 100/ W1

whereas W1 is original dried sample weight,

W2 is the final weight of the sample after immersed in the boiling water.

Green MOR Test:

This test is to find the green Modulus of rupture of the ball clay. The formula used to find the Green MOR is

MOR = 8 x P x L / ,

 

L is the length in cm;

 

D is the diameter of the bar in cm.

Casting Rate:

To find the slip casting rate for an hour. Less than 20 Thixo slip is made by adding sodium silicate to the ball slip at 1.8 density. This ball clay slip is poured into a plaster mould and left for an hour and then drained, and left half an hour for drying then the casting rate is found by using vernier scale.

Find more tests taken in sanitaryware products here.

Ball Clay Suppliers:

We have listed below some supplier of ball clay from around the world,

• • Imerys ceramics India Private Ltd. – IndiaAddress: Surya arcade, 4th floor,Begumpet,Hyderabad – 500016,India.Contact No: 040-30586666, 30689851, 30689877, 30682266, 30689880,07702070088, 09959911833
  • Kothari Clay industries. – Gujarat, India.Contact Person: Mr Chetan KothariAddress: Mahalaxmi Street, Post Office, Thangadh – 363530, Gujarat, India.Contact No: 09825393663, 02751-220263/220863Fax: 02751-220263
  • Ashvin ceramics. – India

• • Swastik Minerals. – India

• Amarnath Industries. – IndiaContact Person: Mr Amarnath JhaAddress: Behind Arya Samaj School, Rathkhana Colony, Bikaner – 334001, Rajasthan, India.Contact No: 09414147777
• Old Hickory Clay Company – USAAddress: 962 State Route 1241 Mayfield, KY 42066, USA.Contact No: 800-242-6885
• Jannat Enterprise – Malaysia Address: kulim, Kedah, Malaysia.Contact No: 60-50230-15
• Advance Clay Supplies – Malaysia Contact Person: Abdullah HassanAddress: Gombak, Kuala Lumpur, Malaysia, Zip code:68100.Contact No: 60-10-9828969, 60-109828969
• Mita Madencilik Ltd – Turkey Address : Eskisehir, Seyitgazi, Turkey, Zip Code: 2600Contact Person:Takittin ErolTelephone:90-252-3822744Fax: 90-252-3824211

Functions: The major functions of the ball and plastic clays in ceramic bodies are:

• Provide fine particles
• Higher plasticity and workability
• Higher dry and lower fired shrinkages
• Higher unfired strength
• Make ceramic bodies buff burning, low maturing and less translucent due to the presence of a large number of impurities.

Ball clays are also essential in tileware bodies for plasticity and workability for pressing and unfired strength required for the handling of pressed tiles.

Uses of Ball clay:

Used as a raw material in sanitary ware production.

Ball clay is an essential raw material in sanitaryware production due to its green strength. It gives the sanitaryware handling strength in the green stage. Around 20% were used in the composition of sanitaryware production.

Used as a raw material in wall & floor tiles production

Around 14% used in floors and wall tiles production to give better particle size distribution for better density and whiteness to the product.

Used as a Raw material in Refractory Production

Because of the plasticity property of the ball clays, it is used in the refractory bricks production to give shaping to the product.

Used as Raw material in Ceramic clay pipe production

Due to the shaping property, it is used in ceramic clay pipe production.

Used as a raw material in Electrical insulators

it is used in electrical insulator production to give the insulation properties to the insulator.

Used in Tableware production

One of the raw material for the production of tableware. It gives better shaping and green strength to the tableware product.

Used as other than ceramic industries as filler & extender

Ball clay used in other than ceramic industries for its binding properties. It is used as a filler in paint, fertiliser, etc..

Conclusion:

In this article we tried to cover as much as possible about ball clay, we know that nothing is perfect everything can be improved further so if you feel that we missed something that you like to add in this article please leave your comment below. Find more details about China clay here.