Watermelon Lime Cold Process Soap

This summer it seems like everyone and their neighbor's uncle is making some sort of watermelon themed soap (you know, soap that looks like the real thing). But instead of making a soap that only looked or smelled like a watermelon. I wondered if it would work to put actual watermelon juice in there.

It did, and combined with a juicy blend of lime essential oil it makes for the perfect summer soap.

Using fruit juices to make cold process soap

Now, why does it not always work out to put fruit juice in your cold process soap?

Lye is a strong alkali (ph 13-14), usually we use water which is neutral (ph 7) to make our lye solution. But what happens if we use a very acidic liquid, like let's say lemon juice (ph 2), to mix our lye with?

Well, not much happens at all, actually. The strong acidic (lemon juice) cancels out the strong alkali (lye), if you will. A sign of that is that your lye solution doesn't heat up at first like it should. The soap batter might not emulsify or if it does, the soap will most likely not saponify leaving you with a very soft gooey mess.

Back to our watermelon. Watermelon is alkali (ph 9) which is good news for us, because it means that our lye will (hopefully) work just fine and give us some lovely soap. Watermelon mostly consists of water and sugar. That means that we will have a nice fluid liquid to mix our lye in AND some lovely sudsy bubbles once the soap is finished, thanks to the sugar.

Are you excited to give the watermelon lime soap a try? I am. Let's go!

If you've never made cold process soap before, make sure to check out my posts on lye safety, my beginner's tutorial and list of equipment needed.

Disclaimer: This post may contain affiliate links, meaning at no additional cost to you, will I earn a commission if you click through and make a purchase. 

What you'll need:

Equipment:

• two heat resistant containers (non aluminum) - a smaller one to mix your lye and a bigger one (50 oz capacity) to melt your oils and mix your soap in
• stick blender
• blender (to blend up your watermelon)
• Crafter's Choice silicone loaf mold
• silicone spatula

Recipe for Watermelon Lime Soap:

This recipe has been sized to make around 42 oz of watermelon lime soap (8 standard sized bars), you can resize this recipe to your heart's desire using a soap calculator. Make sure to run every soap recipe you find online (including this one) through a lye calculator, just to be safe.

This recipe uses a 35% lye concentration and is superfatted at 6%.

• Watermelon (blended and cooled): 7.5 oz. / 212 g
• Lye: 4 oz. / 114 g
• Coconut oil: 9.3 oz. / 263 g (32%)
• Shea butter:  7.3 oz. / 206 g (25%)
• Rice bran oil: 7 oz. / 197 g (24%)
• Avocado oil: 3.8 oz. / 107 g (13%)
• Castor oil: 1.8 oz. / 49 g (6%)
• Lime essential oil: 21 g
• Patchouli essential oil: 7 g
• Poppy seeds: 1 - 1 ½ Tbsp
• Kaolin clay: 3 Tbsp

Instructions:

1. Safety First: Put on your googles and gloves and make sure you're not soaping around children and/or pets. Keep your space ventilated or soap outdoors
2. Weigh out approximately how much watermelon you'll need, cut into small pieces, remove any seeds and blend it up until fully liquefied
3. Now, weigh your watermelon juice again and adjust as needed
4. Place container with juice in the freezer and wait until you have an almost frozen slushy
5. Slowly and carefully add the lye, gently stirring until fully dissolved
6. Place lye solution in an ice bath to avoid scorching
7. Melt coconut oil and shea butter over low heat
8. Add avocado, rice bran and castor oil
9. Add essential oils
10. Add kaolin clay and mix until there are no more clumps
11. When lye solution and oils are about room temperature combine the two and stick blend until medium trace (thin pudding consistency) is achieved
12. Now, gently stir in the poppy seeds using a whisk or spatula
13. Pour soap batter into mold and tap it down a couple of times to release any air bubbles
14. Deck out the top, I used the back of a small spoon to created little wavy ridges
15. Insulate mold or place into oven at low heat, check frequently for signs of overheating or cracking
16. Cut into bars after 24-36 hours and cure for 3-4 weeks
17. Enjoy!

Until next time. Happy Tinkering!