If we want to use hard water for textile dye processing, we  need to remove hardness of water at first.

There are two types of hardness.

1. Temporary hardness
2. Permanent hardness. 

Removal of hardness of water:

For Temporary hardness:

Temporary hardness  is caused by Calcium hydrogen carbonate (Ca(HCO₃)₂) or Magnesium hydrogen carbonate (Mg(HCO₃)₂).

For making this  Temporary water to soft water, we have to  boiling this water  or make by using calcium reaction like

1. Ca(HCO₃)₂ + Ca(OH)₂ → 2CaCO₃ ↓ +2H₂O

2. Mg(HCO₃)₂ + 2Ca(OH)₂ → 2MgCO₃ +2H₂O

3. MgCO₃ + Ca(OH)₂ → Mg(OH)₂ + CaCO₃ 

For Permanent hardness:

 is caused by calcium sulfate (CaSO₄) or magnesium sulfate (MgSO₄ ).

1.CaSO₄ + Na₂CO₃ → CaCO₃+ Na₂SO₄ 

2.MgSO₄ + Na₂CO₃ → MgCO₃+ Na₂SO₄ 

3.MgCO₃ + Ca(OH)₂ → Mg(OH)₂ +  CaCO₃ 

Frim the above process we can see, temporary hardness of water can remove by both boiling and temporary treatment process but permanent hardness of water can  remove by the chemical treatment process only.