Rebatching or Handmilling Soap (on purpose)

a.k.a. Temporary Loss of Reason

Experimenting with soap making and homemade creams, salves, and personal care products is something I really enjoy. Part of the appeal is to the geeky side of me, understanding how and why things work, and part of it is discovering the connection to what nature and Mother Earth offers.

Soap making involves a chemical reaction and I wish what I learned in chemistry decades ago stayed in my brain to properly explain how fats & oils (fatty acids or triglycerides) combine with sodium hydroxide & water (and other liquids such as milk) to produce the salt + glycerine we know as ‘soap’. Salt in this case is a term in chemistry not to be confused with what we know as salt used in seasoning.

That satisfies the science nerd, and then there’s the addition of essential oils and other additives that raise soap from utility to luxury.

I’ve used essential oils off and on for decades mostly as nice smelling stuff in a bath or included in products reputed to alleviate a stuffy nose or soothe nerves, but had never looked to them as therapeutic. That seemed a little woowoo to me. However, at the same time, I was a long time gardener with a particular interest in native plants, edible & medicinal plants, and familiarity with the efficacy of herbal teas, infusions, and tinctures. These are based on a body of herbal lore across many cultures dating back thousands of years. Many of the beneficial properties cited for essential oils often are based on the history of the plant herbal rather than experience with the essential oil itself. That being said, essential oils have been studied in the past decades by herbalists, aromatherapists, and researchers based in universities & industry and found to be effective. One company, Nestlé has tried to patent compounds in a nigella sativa, a plant that has been used for thousands of years as a treatment for various maladies.

For that reason, I’ve been adding essential oils to the soap I made partly as a scent and partly for the therapeutic properties. One of those properties is aromatherapy–our olfactory system (the nose and all the cells contributing to our sense of smell) carries molecules to our brain and receptor sites in the brain. One of those sites is the limbic system–you know how a scent can trigger a memory or feeling? That’s the ’emotional brain’ or limbic system and is connected to the parts that control heart beat, memory, breathing, stress and hormone balance. When you smell a soap and go ‘ahhh!’ think limbic.

The chemical reaction of saponification involves the very caustic sodium hydroxide and fatty acids, and even though the essential oils are added at ‘trace’ there is substantial degradation of their properties. Most soapcrafters add 40-50 grams (per 1000 grams of soap) of essential oil which can not only be expensive for some EOs but may be so delicate to not come through the process. It occurred to me that the process of rebatching or handmilling the soap might be a way to not only use less EO but also enjoy more of the benefits of their properties despite being a wash off skin care product. So, after embarking on an odyssey of Youtube videos, asking questions, and reading blogs, it was time to just do it.

Let’s do it!

There appear to be three commonly used methods of rebatching soap: in a crockpot, in the oven, in a bag in boiling water. So, having nothing better to do, why not do all three and see which works best? Also, it gave me the opportunity to incorporate different essential oils and additives. The Basic Tallow Soap I made the other day was divided into three pieces of 440 grams each; the blocks were grated using a box grater. It was like grating soft mozzarella cheese in case you’re wondering: easy. The essential oils blends were weighed and set aside. Three molds were lined with plastic wrap; the bottom of the box for the honey-oatmeal batch was lined with bubble wrap facing up to simulate a honeycomb effect.


Batch #1 Crockpot

1/4 c colloidal oatmeal
2 tbsp natural honey
5 gr Clove (eugenia caryophyllata)
10 gr Orange Sweet (citrus sinensis)
10 gr Sweet almond oil (prunus dulcis)

The crockpot is a programmable model that has four settings: high (212F), low (200F), simmer (185F), and warm (165F). A little crockpot trivia: heat settings mean different temperatures on each crockpot model. Older ones (~1970s) probably cook at lower temperatures if their thermostat still works. Newer ones like mine were produced after manufacturers were afraid of liability from consumers cooking food at low temperatures and they caution not to cook on warm. For the purposes of soap rebatching warm is ideal however. The grated soap was added along with 50 ml of water, lightly tossed, covered with lid and set to go.

melting soap in crockpot

After 45 minutes

This took an hour and 10 minutes to cook to a state I felt was suitable for working with; the oatmeal was sifted into the soap and stirred well. The honey was stirred into the oils and then everything into the soap. Stirring it as quickly & thoroughly as possible I was nervous about whether it would seize because of the clove oil, however, it mixed up well and was pressed into the box lined with bubble wrap, and then another piece of bubble wrap was pressed on top bubble side down.

honey oatmeal soap

Honey Oatmeal Soap

The finished bars are um, rustic looking, and have a honeycomb appearance from the bubble wrap and smell nicely of orange and clove. As with all the bars, they’re very soft even two weeks later, but these seem moreso maybe because of the honey. It will take several months to harden by the feel of them.


Batch #2 Oven

10 gr Sweet almond oil (prunus dulcis)
5 gr Eucalyptus (eucalyptus radiata)
5 gr Rosemary Spanish (romarinus officinalis)
5 gr Lavender Bulgarian (lavandula angustifolia)

melting soap in oven

After 45 minutes

The oven was set at 170F and the grated soap was put into a casserole dish along with 50 ml of water, lightly tossed, covered with lid and put in oven.

This took the longest at almost 2 hours but the texture was the nicest; however it probably could have continued to cook longer to be softer. The essential oils were mixed in and quickly stirring the mixture it took on almost a creamy white colour. It was pressed into the mold with a piece of waxed paper on top.

eucalyptus and lavender soap

Eucalytus & Lavender Soap

These will be wonderful when winter comes because the eucalyptus overpowers the other two essential oils (yowza!). Live & learn. If you’re making this, use less eucalytus. Or more of something else. Unless you have a cold in which case these will be lovely smelling in the shower. The finished bar has a smoother texture than the other two and I pressed a star anise into them to create a pattern; also they were cut into little bars. Just because.


Batch #3 Boil in a Bag

10 gr Black Cumin Seed (nigella sativa)
3 gr Sea Buckthorn (CO2) (hippophae rhamnoides)
5 gr Tea Tree Australian (meleleuca alternifolia)
5 gr Lavender Bulgarian (lavandula angustifolia)

melting soap in bag

After just 20 minutes!

Added grated soap to a ziploc freezer bag along with 50 ml water, mushed it around, pressed the air out and then put it in another ziploc freezer bag. (Because: Murphy’s Law.) Set in a large pot of simmering water and covered with lid.

essential oils blended in bag of soap

After 45 minutes

After 45 minutes, it’s approaching liquid soap state so I removed it from the water, mushed it around and added the essential oils; the sea buckthorn oil deeply coloured the soap. After thoroughly kneading the plastic bag, I cut a corner off the bag and squeezed it into the mold, spread it out and pressed plastic wrap on top.

sea buckthorn soap

Sea Buckthorn Soap

The tea tree seems to have won the battle of scents in this bar but that’s okay–it was meant to be for skin care, specifically rosacea, and we’re used to a strongly scented bar for that use. The sea buckthorn oil is the source of the deep yellow colour. The texture is smooth like the eucalyptus bar, and will also need several months to harden.



Overall this was an interesting experiment and taught me a lot about rebatching and using essential oils. Main observations for next time: use less water and probably less carrier oil. And, I need to learn more about blending essential oils. The boil in a bag approach was fastest and will be the preferred method if I ever do this again, either on purpose or to salvage a soap mess. 

Finally …

shavings and ends of soap bars

Soap ends & shavings

Sometimes when I see the beautiful posts of soap on blogs & forums it makes me envious of the creativity and expertise of the soapcrafters. If you’re a newbie like me here’s a pic of what’s left after carefully trimming the bars to make them camera and shower ready. Don’t feel so bad now, eh?

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About Leslie

Trying a little bit of everything: writing, learning Wordpress & basic coding, cooking, playing with grandkids, travelling, gardening, making soap & body treats, and getting older. Not necessarily in that order.