Making Laundry Soap from Recycled Olive Oil (Castile Soap)

Bins for used oil are placed throughout town in order to stop people from pouring used oil down the drain or in the trash.  However, when the used oil is olive oil, it´s only more incentive for me to recycle it myself into laundry soap.  Olive oil is not just more expensive but the soap made from it would have a longer shelf life as compared to sunflower oil.  I decided to show a few friends how simple it can be done and hopefully get them to recycle oil in their home and save money on laundry soap as an extra benefit.  I hope this blog post reaches others interested in recycling their used oil into something as useful as laundry soap.

In order to make the soap appropriate for laundry, I didn´t want any leftover oil to hinder it´s cleansing potential in clothes.  So, I calculated (soapcalc link on the sidebar) the recipe for 0% superfat and reduced the water percentage to 20% because I plan on using liquid fabric softener as the fragrance.  At first I calculated the recipe for 1 liter (1000 gr.) of oil and then I readjust the quantity accordingly.  The final recipe is as follows:

4000 gr. olive oil
  800 gr. tap water
  544 gr. lye granules (NaOH)
  380 gr. rose-scented fabric softener

Note: I had rounded up the lye amount per liter of oil to 136 gr.  That´s how I arrived at 544 gr. lye in the recipe (136 x 4).  I don´t think this would affect the final laundry soap result.  When pouring the lye water into the oil, there is always some lye water that stays behind with the container and doesn´t get to the oil, the couple of extra grams of lye is actually a good thing when making laundry soap.

The oil, which has been previously strained to remove solid bits of food particles, is at room temperature and in the black bucket while the lye is being mixed in with the tap water in the blue bucket.  Once the lye is dissolved, carefully add it to the oil.  The lye water is hot, so handle with care and wear gloves to protect against any splashing.

The stick blender is very helpful in speeding up trace.  It turns into a beautiful yellow cream.  This is when the fabric softener is added to give it a nice scent.

Once it reaches a thicker consistency much like vanilla pudding, pour the batter into the molds.  We used empty milk cartons which have been reinforced with some masking tape to give them more stability from bulging. The plastic ice-cream containers are another great option and they have lids for easier storage once the soap is cured.

After 3 days, I unmolded one of the milk cartons. It is soft like semi-cured cheese and stuck to the carton; I was scraping and sticking the soap pieces back as I peeled off the carton.  It won´t be easy to remove the soap without deforming them, so the others will sit in their containers to cure.

I am very happy at how they came out!  It lathers nicely, pH 7-8 and smells good and clean. The way a good soap ought to be.