Soap made of used cooking oil

Don't throw away any cooking oil that had been used. We can recycle it as soap.

Prepare:
225ml water
75gr caustic soda (soda api)
500ml used cooking oil
Favourite perfume as desired

Steps:
1. Pour water into a bowl
2. Then put in caustic soda & stir until dissolve (caution not to spill caustic soda to hand coz my result skin irritation)
3. Slowly pour in the used cooking oil while keep stirring until all cooking oil is poured in & the liquid is thickening
4. Put in about 2 or 3 drops of desired perfume for a hint of fragrant. Stir until all mixed in well.
5. Pour mixture into desired shape bowl & let it until completely dry (take about few days)
6. It's advisable to wait about 3weeks before using the soap so that it's ph balance will not cause skin irritation. Soap can be used to wash hands & other things but not advisable for face.