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5 from 2 votes

Garden Rhubarb Soap Recipe

Simple cold-process soap recipe using garden rhubarb root to achieve a soft pink color. Makes approximately six bars. Technical information: 1lb / 454g batch -- 5% superfat -- 35.7% water discount
Course Soap recipe
Keyword Rhubarb, soap, soap recipe
Prep Time 30 minutes
Cook Time 30 minutes
Curing time 28 days
Total Time 1 hour
Servings 6 bars
Author Lovely Greens
Cost 10

Equipment

Ingredients

Rhubarb-infused oil

Lye solution

Solid oils

Liquid oils

At Trace

Instructions

Make rhubarb-infused oil

  • To make pink rhubarb soap, you will first need to infuse the olive oil called for in the recipe with dried rhubarb root. The ratio of root to ratio is quite low, and infusing them is very easy. The process extracts the colored components from the root, but the pink color will not be evident until the lye solution is added to the oils during the soap-making process.
  • Cold infusion instructions: Fill a Mason jar with the rhubarb powder and oil. Seal it and leave it in a dark cupboard for four or more weeks. I gave it a couple of shakes during that time, but you could shake yours more if you wish.
  • Warm infusion instruction: Fill a Mason jar with the rhubarb powder and oil. Seal and gently heat it in a bain-marie for twelve hours. The easiest way to do this is to set a cloth at the bottom of a crock pot, half-fill the crock pot with water, and place the sealed Mason jar inside and on the cloth. Set the temperature to hot to warm the water, but reduce the heat to warm after one hour.
  • When the time is up, strain the oil from the rhubarb root. It will have a yellowish tinge, but it won't be as yellow as when making Himalayan rhubarb soap. Discard the rhubarb pieces/powder and store the strained oil in a clean jar for as long as the original shelf-life of the oil. You can use it to make garden rhubarb soap immediately, and you should have enough to make two 1-lb batches of soap. The infused oil can replace all or some of the olive oil called for in soap recipes. The more of it you use, the pinker the soap will be.

Make Rhubarb Soap

  • Cold-process soapmaking is chemistry, and this recipe uses lye. Lye is a caustic substance that is completely neutralized in the soapmaking process, but it can be harmful if not handled correctly. Please read this soap making safety guidance before proceeding.
  • Prepare your workstation with your tools and equipment. Put on rubber gloves, eye protection, and an apron. Carefully pre-measure the ingredients. The solid oils into the pot, the liquid oils into a jug, the water into another heat-proof jug, and the lye in another container.
  • Next, dissolve the lye (Sodium hydroxide) crystals in water. In an airy place (outdoors or by a window is best), pour the lye crystals into the water and stir well. There will be a lot of heat and steam, so be careful. Try not to breathe it in. Leave to cool. I tend to set my jug in a sink shallowly filled with cold water.
  • Melt the solid oils in a stainless steel pan on very low heat. When melted, remove from the heat and set on a potholder. Pour in the liquid oils. If you have the olive and castor oils in the same container, stir them together before pouring them into the pan. Castor oil is sticky and easier to pour when mixed with lighter consistency oil.
  • Measure the temperatures of the lye solution and the oils. You should aim to cool both to about 100°F (38°C).
  • Pour the lye solution into the pan of oils. I recommend pouring the liquid through a small sieve to catch any potential undissolved lye.
  • Next, we're going to bring the soap to 'trace.' It involves alternating stirring then pulsing the ingredients until they thicken to the consistency of warm custard. At trace, the soap batter will leave a distinguishable trail on the surface if you drizzle it from the immersion blender head. You will also see the pink color come to life in this step.
  • Dip the stick blender into the pan, and with it turned off, stir the mixture together. Next, bring it to the center of the pan, and with both your hands, hold it against the bottom of the pan and blitz it for just a couple of seconds. Please don't move the blender around when turned on since it sends up splatters in small soap batches. Turn the blender off and stir the soap batter using as if it were a spoon. Repeat until the mixture thickens up to 'Trace.'
  • Working quickly, stir the essential oil in if you're using it, then pour the soap into the mold. Give it a tap to settle it.
  • You have a choice, now. To potentially deepen the soap color, you can encourage the soap to gel. I do this by placing the mold in a pre-warmed oven (warmed to 170°F) that's been turned off and leaving it there overnight. For a lighter true-pink, put the soap mold in the refrigerator overnight. The bottom shelf is best, and putting it in a large tupperware or covering it with clingfilm will stop the essential oil scent from contaminating the fridge.
  • The next day, take the soap out of where it is and set it somewhere to rest for another day. Once 48 hours have passed, you can take the soap out of the mold and cut it into bars using a kitchen knife. You can get five to six decent-sized bars of soap from this batch.
  • Cure the rhubarb soap for 28 days. Curing means leaving the bars spaced out on a protected surface out of direct sunlight and in an airy place. This allows the extra water content to evaporate out fully. Here are full instructions on how to cure soap.
  • Once made, your soap will have a shelf-life of up to two years. Check the oil bottles and packaging that you're using, though. The closest best-by date is the best-by date of your soap.

Notes

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