Effect of water quality in the Ceramic Industry

We use a massive amount of water during the production process of Ceramic Products. (Am specially referring to Ceramics tiles manufacturing)

So, does the quality of water affect to the final quality of the product?

Water is mainly used for,

1. Body Preparation
2. Glaze/Engobe Preparation
3. Washing of machinery

As per the production process and the usage, the quality of water will not affect to any quality parameter during the process of body preparation as almost all the water will be removed during spray drying (powder production) and as all the materials are soil related. 

But what about Engobe / Glaze preparation? 

Glaze is the top most layer of the tile and it is the part which exposed to the environment and the end user. the Glaze is a sensitive layer to firing temperature, oxygen amount when firing takes place, the soaking time, any materials to be evaporated through the glaze, etc.

So, the glaze could be affected by all above parameters and could have an impact to the final surface quality of the fired product's surface.

Glazes are produced using mainly non-reactive metal alkoxides (called as "Frits"), processed clay/Kaolin, Zirconium Dioxide, Naphalene, Corundum, other required additives and water.

the grinding process is done with water inside ball mills. 

The used water maybe drawn from mainly industrial wells / tube wells with underground water. Some industries use filters to filter the water and some are not. Filters will remove any particles from the water including, mud particles, some iron particles, some mineral particles, etc. But the water will not be totally purified. The soluble salts would be present in the filtered water also. 

What are soluble salts?

This term  refers to all those carbonates,  sulphates and alkaline/alkaline-earth chlorides soluble in water. This capacity varies enormously from mineral to mineral: values are sometimes so low (in the order of just a few parts per thousand) that they are, to all intents and purposes, insoluble.

The most important soluble salts are:

• Ca, Mg, Na, K and Al sulphates
• Na-Al, K-Al double sulphates
• Ca, Na and K carbonates
• Na and K chlorides.

Among these, calcium carbonate  (its definition as a soluble  salt considered by some to be improper) is present in all the clays used to produce porous bodies. 

Solubility of salts in water

Mineral	Solubility (g/l)
CaCO3	0.013
CaCl2	595.0
Ca(OH)2	1.850
CaMg(CO3)2	0.320
CaSO4	2.090
CaS04 . 2H20	2.410
BaCO3	0.020
BaCl2	310.0
BaS04	0.002
MgCO3	0.106
MgCl2	542.5
MgSO4	260.0
Mg(OH)2	0.009
Na2C03	71.0
NaCl	357.0
Na2SO4	47.6
K2CO3	1120.0
KCl	347.0
K2SO4	68.5

Back to the Topic
As you can see, the highest solubility is with Chlorides. But it is known that, chlorides for some extent, does not effect to any quality problems, But excessive amount of chlorides will cause problems in the operational stage. (eg: the glazes may tend to thicken/agglomerate due to high amount of chlorides, etc) 

The amount of soluble salts in the water used is found to affect the final surface quality of the glaze of the ware. (Sanitary, tableware, tiles)

The affects are occurred by 2 factors.

• Ca++, Mg++ ions (which the water will be hard)
• Sulphates in the water (SO4--)

Tests are being carried out to identify the effect of soluble salts to the final product quality of glazed ceramic tiles.  --
Cont'd