Hardening solution for agar:
Gypsum products are not compatible with the hydrocolloid impression materials. The casts will become soft. This can be prevented by incorporating hardening solutions in the impression material during manufacturing or by immersing the impression in an accelerator solution for the setting of gypsum.
The hardening solutions are 2% potassium sulphate for agar and titanium fluoride for alginate materials.
Titanium flouride.
Sodium flouride.
2% potassium sulphate.
All of the above.