If I want to use hard water for my textile dye processing, at first I  need to make hard water into soft water through different reactions for good results.

Water can be hard in two ways. They are:

1.Temporary hardness

2.permanent hardness. 

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 

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