YIELD: 8-9 bars 
Castile [ka-steel] soap is one of the oldest types of soap. It is a natural soap made from 100% olive oil, which is a soft oil, so this soap needs a longer storage period before use to get maximum lather. You can use olive oil or extra virgin olive oil from local growers - olive oil soap will be darker and have a green hue when compared to extra virgin olive oil soap which has a pale yellow to green hue.
15g (0.5oz) sea salt
310g (11oz) distilled water
120g (4oz) lye
935g (33oz) extra virgin olive oil
42g (1.5oz) skin-safe essential oil/s (optional)
Rubbing alcohol in a spray bottle
1. Safety before you start: always wear safety gear whilst making soap in a well-ventilated space, as outlined in Lye & Safety
2. Dissolve salt in water in a plastic bucket (lye bucket). Add lye and cool to 57°C (135°F).
3. Measure oil into a second bucket (soap-making bucket). Add cooled lye solution and blend for 20-60 seconds until thin trace is achieved.
4. Whisk through essential oil/s.
5. Pour soap into mould/s. Spray surface with rubbing alcohol. Cover loosely with a cloth (not touching the surface) or fold over the tops of the milk carton. Wrap cartons with towels.
6. Set aside to dry for 2-3 days. Slice when firm enough to cut (but not sticky) and stamp if required.
7. Cure on a coated wire rack away from heat and sunlight for 3-5 weeks, turning weekly.
8. Wrap and store finished soap. This soap firms after several months, and is best used after 9-12 months.

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