Welcome to the Q&A follow-up post for my Super Simple Natural Lotion formulation! Today I’m tackling some of the questions I got about this formulation that were not answered in the original blog post or video. Can you add goat milk powder? How about using a different preservative? Keep reading to find out!
For reference, here’s the formulation we’re talking about today:
Super Simple All Natural Lotion
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If I want to add essential oils (or fragrance oils), when should I add them?
Add any essential oils to the cool down phase with the preservative, and then carry on with testing and adjusting the pH (if required). Adding a small percentage of essential oils to the formulation will not meaningfully impact the pH of your lotion. Essential oils don’t have a pH value as they are not water soluble.
Make room for essential oils in your formulation by reducing the amount of distilled water. For example, if you wanted to include 0.5% essential oils you would reduce the water to 68.2% and add 0.5% essential oil(s) to the cool down phase. Be sure you are following safe dilution rates for the specific essential oils you’re working with (more on that here). I generally use ≤1% essential/fragrance oils for leave-on applications.
Could I add powdered goat milk?
You can definitely try it! The main concern with incorporating milk of any kind into a formulation is stability as milk is not known for being super shelf-stable, so you’ll have to try it and then monitor the formulation for stability.
When starting to formulate with a new ingredient, a great way to get an idea for what can work is looking at sample formulations from suppliers and manufacturers. Lotion Crafter has a goat milk lotion formulation on their website and they note the “formula has passed a USP 51 Preservative Efficacy Test”.
The formulation from Lotion Crafter uses 1% goat milk powder in their heated water phase, and that seems like a good place to start. Drop 1% of the distilled water to make room for the milk powder.
You’ll notice the Lotion Crafter formulation includes a chelator (Disodium EDTA)—I’d probably incorporate one as well. They use Euxyl® PE 9010 (Phenoxyethanol [and] Ethylhexylglycerin), Potassium Sorbate, and Sodium Benzoate to preserve the formulation, and recommend a final pH of 4.5
It could also be a good idea to modify the formulation a bit to improve the stability of the finished product. You can learn more about formulation strategies to improve stability here and here. They include reducing water activity, good manufacturing practice (GMP), pH, and packaging—definitely read the linked articles to learn more!
Could I use just phenoxyethanol as my preservative? Could I use Geogard Ultra as my preservative instead of Geogard ECT?
Using a different preservative is always a bit of an “it depends, research it, try it, and see” sort of deal. I’ve written an entire FAQ on that here.
For this particular formulation there are a few characteristics to keep in mind:
- Our emulsifier is anionic, so any preservatives that don’t work in anionic formulations should be avoided.
- Our emulsifier doesn’t work if the pH of the formulation goes much below 4, so preservatives that work best below 4 and/or preservatives that can cause the pH to drop below 4 can be problematic.
- The formulation is relatively simple; as written, it doesn’t contain a lot of hard-to-preserve ingredients.
I don’t have a ton of experience using phenoxyethanol as the sole preservative in formulations, but it was one of the preservatives I tested in a year-long preservative experimented I documented and shared with my $10 and up patrons. It worked well in that experiment, so I’d say give it a try and see if it works.
I used Geogard Ultra in my first draft of this emulsion. I included it in the heated water phase as it takes quite a while to dissolve, and that made the formulation so acidic that it never emulsified. I wanted to avoid the possibility of a failed emulsion as much as possible with a “super simple” formulation that was designed to be beginner-friendly, so I decided to pivot to Geogard ECT as I could add it to the cool-down phase easily and adjust the pH from there. Even without L-Arginine the ECT didn’t make this emulsion acidic enough to fail. I’m sure you could get Geogard Ultra to work, but that’s why I didn’t use it for this formulation.
Which ingredients impact the pH of a formulation?
pH is a bit like flavour; the entire formulation is important, but some ingredients are more potent than others (think spices v.s. broth). The more extreme the pH of the ingredient, and the more of an ingredient that is used, the more that ingredient will impact the pH of your formulation. To continue the flavour analogy—a tablespoon of ground cumin would very noticeably impact the flavour of a pot of soup, while a tablespoon of broth likely wouldn’t be noticed.
Water-soluble ingredients with strongly acidic or basic pH values (lower than 3/4 or higher than 9/10) are the “spices” of our formulations. These will impact the pH of your formulations even at small concentrations. Examples include citric acid, lactic acid, ascorbic acid (vitamin C), some preservatives (definitely both Geogard ECT and Geogard Ultra), sodium hydroxide, triethanolamine, carbomer, L-Arginine, baking soda, and some surfactants.
For instance, while I was working on my Oat & Shea Hand Lotion I found that including 0.2% of very acidic citric acid in the formulation was enough to lower the pH from 8.14 to 5.27. As pH is logarithmic, that’s a difference of roughly 1000x! That’s a pretty massive pH change for a 0.2% shift to the formulation.
When I’m formulating with basic surfactants like Sodium Coco Sulfate (SCS) or Decyl Glucoside I usually include a bit of citric or lactic acid right off the bat, and adjust the amount as I work on the formulation. I do this because I know the basic pH of the surfactant will raise the pH of the formulation.
Can I add anti-ageing ingredients?
This is another “it depends” as the category of “anti-ageing ingredients” is quite vast! You’ll need to start by researching the new ingredient you want to include. The Humblebee & Me DIY Encyclopedia is a great place to start this research!
This list is taken from my FAQ “How can I incorporate X ingredient into a formulation?“:
- What is it soluble in?
- What is the recommended usage rate?
- Is it heat-sensitive?
- What is its pH?
- Does it need a certain pH to work?
- What is its charge?
- Is there anything the ingredient explicitly cannot be used with?
Let’s look at each of these points in the context of this formulation.
- This formulation has both a water phase and an oil phase, so any oil or water-soluble active could work as it will have a compatible solvent.
- Usage rates for actives are provided as ranges; I generally recommend starting in the middle of the range unless the ingredient has irritation potential and/or is very expensive, in which case I’d start at the bottom of the range.
- The heat sensitivity of the ingredient will determine which phase you include it in; a heated phase, or the cool-down phase. If the ingredient is heat stable you don’t necessarily have to put it in its matching phase. For instance, I’ll often put gums into the heated oil phase for emulsions because they can’t clump there—they’ll incorporate and dissolve into the water when the phases are blended together.
- If the active ingredient has a pH that is dramatically different than the desired pH of the formulation you will likely need to test and adjust the formulation. If your active is quite basic you might be able to drop the L-Arginine and let the active raise the pH of the formulation; if the active is quite acidic you may need more L-Arginine.
- As written, the pH of this formulation is around 5–5.5, which works for the emulsifier and the preservative. If your active ingredient has a required pH range to function—does it match? Can the pH the active needs overlap with the pH the emulsifier and the preservative need? If not, you’ll need to re-formulate in order to include the active.
- Since our emulsifier is anionic (negatively charged) you’ll want to tread carefully with incorporating any cationic (positively charged) ingredients.
- Does the documentation for the active ingredient explicitly state it shouldn’t be combined with anything that is present in this formulation? Does it have any other requirements that will need to be accommodated? Does it have any characteristics that could be challenging to the formulation (high electrolyte content is a good thing to keep an eye out for)?
If you’ve done your research and it hasn’t raised any red flags, you’ll know how much of the new ingredient to use, and which phase to include it in. Adjust the formulation to make room for it (generally by reducing the distilled water), and off you go! Make it, take heaps of notes, and see what you think.
It’s often tempting to incorporate ALL THE ACTIVES, but if you are working with a new ingredient I recommend starting simple and slow to start with. If you include actives A, B, C, and D in a formulation you might never know that active C is irritating your skin, negating the beneficial effect that active A might’ve had if it was on its own—or that perhaps A + D would be magic for your skin on their own, and B & C are totally unnecessary.
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Relevant links & further reading
- Super Simple Natural Lotion
- Super Simple Moisturizing Lotion
- Super Simple Moisturizing Lotion with Glyceryl Stearate (and) PEG-100 Stearate
- Why didn’t my lotion emulsify?
- How can I make this thicker/harder/firmer?
- How can I make this thinner/softer/less viscous?
- What can I use instead of water?
- Can I use an essential oil or fragrance oil instead of a carrier oil?
- How much essential oil can I add to this recipe?
- Formulating and DIYing with Spreadsheets
- pH meter in the Humblebee & Me Encyclopedia
- 5 common questions about lotion (video)
- Why did my emulsion fail?
- How can I make this lotion thicker or thinner?
- Can I put this lotion in a pump-top bottle?
- Can I put this face lotion on my hands?
- Can I use a hydrosol instead of water?