How to make soap with used cooking oil

INGREDIENTS:


2 L of used edible oil
1 L of water
1 / 4 cup of soap powder
700g of caustic soda (NaOH)
2.5 mL of flavoring substance (not mandatory)

INSTRUCTIONS:


Dissolve the soap powder in 200ml of hot water
Dissolve the caustic soda in 800ml of hot water
Slowly add the two solutions to the oil
Stir for 20 minutes
Add the flavoring essence
Pour into forms
Desenformar the next day