What has been your most challenging formulation problem?

Anna_Maria

Member

September 22, 2022 at 5:15 am

@Perry also what do you think about trying PEG-150 distearate for thickening?

Pharma

Member

September 22, 2022 at 7:30 pm

Anna_Maria said:

Sodium chloride doesnt work with any of these surfactants right?

Salt should work with sodium methyl cocoyl taurate, sodium cocoyl isethionate, and, most notably, sodium lauroyl methyl isethionate.

@Bill_Toge I am working on a 10% azelaic acid emulsion, using sepimax zen as the main emulsifier/gelling agents. I noticed you had success with butyloctyl salicylate as the solvent. What would be the appropriate usage rate to solubilize the 10% azelaic? Thank you for your help/insight!

ngarayeva001

Member

October 25, 2022 at 6:45 am

I had two, one has already been solved, and another is semi-solved.

1) I desperately wanted to reverse engineer my favourite make up removing balm, which is banila clean it zero:

https://incidecoder.com/products/banila-co-clean-it-zero-original 

many brands have similar products, but there is nothing like banila. My biggest challenge was the availability of the ingredients. After 4 years of trial and error (and definitely over 50 attempts), I finally found low melting point synthetic wax and PEG-10 isostearate. Once I had the right ingredients, it worked after a second attempt.

I did it over 50 times, so you don’t have to:

Ethylhexyl Palmitate	36.00%
Cetyl Ethylhexanoate	35.00%
PEG-20 Glyceryl Triisostearate	12.00%
PEG-10 Isostearate	10.00%
Synthetic Wax	7.00%

2) The second is the stability of my foundations (and W/Si, W/O in general). Here are a couple of tricks that I learned:
- use several emulsifiers
- oil phase stabiliser is not optional, it’s a must
- repeating common knowledge, the electrolyte in the water phase is a must
- the type of oil matters
- the process matters a lot! It depends on the emulsifier, but in most cases, water is to be added to the oil phase by drops under low-shear mixing, and then it should be exposed to high shear to reduce the size of droplets.
- professional chemists with access to a lab will throw rotten eggs at me, but I am saying it anyway: you don’t need a homogenizer to make a foundation (w/o, w/si). A 600W stick blender will do. An overhead stirrer is a must, though.
- if you want to invest money in something related to w/o, buy a decent microscope to see the shape of droplets. That’s a good predictor of stability in the absence of a lab to run a proper stability test.
- do not add preservatives in the end! It makes no sense, as water is an internal phase!
- PEG-10 dimethicone and ABIL WE 09 MB are amazing
- Stearyl dimethicone (as a stabiliser) = improved aesthetics (IMHO)

Pharma

Member

October 25, 2022 at 6:02 pm

ngarayeva001 said:

…
2) The second is the stability of my foundations (and W/Si, W/O in general). Here are a couple of tricks that I learned:
- use several emulsifiers
- oil phase stabiliser is not optional, it’s a must
- repeating common knowledge, the electrolyte in the water phase is a must
- the type of oil matters
…

Small addition to those four points:

- By preference, one of which should be polymeric (better long-term stability) and one a small monomeric (‘faster’, helps with initial emulsification).

- With probably one exception wherein too much oil gellants make the product feel weird, almost brittle: HIPE emulsions.

- I wouldn’t say electrolytes are a must, but they have, off the top of my head, three different modes of action which all help in diverse ways. Working without them is probably not worth time and effort because, I suspect, there are no suitable and esthetically appealing emulsifiers available. Again, HIPE emulsions are a class of their own and may work without (or at least, without any extra addition besides the active ingredients which may already be electrolytes).

- Theory has it that high polarity oils (ester oils) are better suited than nonpolar oils such as hydrocarbons (squalane probably being the worst). The right choice of oils also helps, according to the HLD system, to reduce the amount of electrolytes needed.

And three more in addition:

- For some weird and, to me, unexplainable reason, fatty alcohols don’t do any good in w/o emulsions.

- Again from the HLD system (haven’t tried it properly myself to be able to confirm this theory): Longer chain glycols (>C6) are allegedly better suited than short chain ones (C2-C5), glycerol and polyols.

- Do not use ionic emulsifiers for several reasons, not even at levels as low as 1/20 of the amount of total emulsifiers added. Seems obvious because they have a high HLB but they sometimes come disguised as part of active ingredients. Smaller additions of nonpolar ones such as Tween-20, another functional additive in active ingredients, also has a high HLB but may be tolerated to a degree.

ngarayeva001

Member

October 25, 2022 at 6:35 pm

Thank you @Pharma! Very helpful. Can you point me to explanation why higher polarity oils are better for w/o? I know the opposite it true for o/w and it would be great to understand the logic.

Pharma

Member

October 25, 2022 at 7:13 pm

HERE is where you can read about the supposed mechanism for this behaviour. It’s not an evident 1+1=2 thing… there seems to be an interaction (or lack thereof) of the oil molecules with the alkyl chain of the emulsifiers (or in the other phase, glycols/polyols with the hydrophilic heads) which push them apart (or let them interact with themselves, respectively). This leads to a shift in appartent HLD/HLB values or, in other words, a different curvature of the interface layer formed by emulsifiers.

Take for example 10 pencils (or a few less) and bind them together with a string forming a ladder (with just one string in the middle) with a spacing of maybe 1-2 cm. The string is the interface whilst the back sides of the pencils represent the oil phase and the cap sides the water phase. If you, as an example, increase the diameter of the caps, the ladder bends to give a o/w droplet. That’s the part you’re certainly familiar with. Now, if you squeeze something between the pencils, the same bending takes place. In a w/o emulsion, we want nothing between the heads in the water but lots of material between the oily tails. What better to use than an oil which has some affinity for the more hydrophilic part and will love to stick close to the interface/string? That’s also the point where fatty alcohols start to create confusion… they should work even better than ester oils but they don’t…

Hope you understand my explanations 😉 .

ngarayeva001

Member

October 26, 2022 at 9:53 am

Sorry, the link is not working.

ngarayeva001

Member

October 26, 2022 at 10:04 am

This is totally anecdotal, but for some reason, I have much more success with w/si emulsions than w/o. I attributed it to the fact that in the case of w/si, I am not guessing which emollient to use but use the one compatible with the emulsifier (a non-polar one). Again, that’s completely anecdotal. I have several foundations that haven’t shown any signs of separation for almost 3 years (and droplets look ok under a microscope). I don’t have a single w/o that lasted this long. Again, as I am not a chemist, I just rely on suppliers’ information and countless trial and error. It would be great to understand the mechanism in deeper detail.

Pharma

Member

October 26, 2022 at 7:10 pm

Without link: http://www.stevenabbott.co.uk

It’s probably also because w/si emulsifiers were designed for cosmetic w/si emulsions whilst w/o emulsifiers tend (at least the older ones) to come from other fields of use, such as the food industry. Long shelf life hasn’t the same meaning in food than it does in cosmetics.

Take for example PGPR: You’ve likely came across this one. Great for processed food but in cosmetics *yikes!*… It has one virtue none of the other cosmetic emulsifiers I’ve seen so far has: It has super long lipophilic tails. This makes it very ‘slow’ (takes time to diffuse to the emulsifier interlayer) but it binds diverse types of oil to the interface, thereby creating a ‘sturdier’ shell around the water droplets. The feel however… I really don’t like it. Also, shelf life is in the range of months, from what I’ve seen so far, and it tends to result in multiple emulsions (o/w/o).

The trick might be to use it at (guessing here) 20% of the amount of your primary emulsifier to notch up your product. However, with PGPR it’s mandatory to combine it with a small, low HLB emulsifier such as a monoglyceride, sorbitan ester, or a di- or triglyceryl mono-, sesqui-, or diester.

The tendency to create multiple emulsions also makes the process (of making the emulsion) more prone to errors and deviations.

chemicalmatt

Member

October 29, 2022 at 4:01 pm

I was tasked with developing a nano-emulsion carrying tolnaftate, the antifungal API to treat nail fungus. Trick was to maintain a low viscosity so this could dispense from an applicator tube. Tolnaftate does not like to dissolve in anything, so I first solved that issue (as in dis-“solved”, pun intended). Formulating a Windsor Type o/w microemulsion was relatively easy since I formulated those for the haircare market many years before. Getting the viscosity to quell - not gel - proved hardest. After many tries, I succeeded. My name is on the patent. The takeaway: packaging matters.

pma

Member

November 2, 2022 at 4:54 am

ngarayeva001 said:

I had two, one has already been solved, and another is semi-solved.

1) I desperately wanted to reverse engineer my favourite make up removing balm, which is banila clean it zero:

https://incidecoder.com/products/banila-co-clean-it-zero-original 

many brands have similar products, but there is nothing like banila. My biggest challenge was the availability of the ingredients. After 4 years of trial and error (and definitely over 50 attempts), I finally found low melting point synthetic wax and PEG-10 isostearate. Once I had the right ingredients, it worked after a second attempt.

I did it over 50 times, so you don’t have to:

Ethylhexyl
Palmitate 36.00%

Cetyl
Ethylhexanoate 35.00%

PEG-20
Glyceryl Triisostearate 12.00%

PEG-10
Isostearate 10.00%

Synthetic Wax 7.00%

2) The second is the stability of my foundations (and W/Si, W/O in general). Here are a couple of tricks that I learned:
- use several emulsifiers
- oil phase stabiliser is not optional, it’s a must
- repeating common knowledge, the electrolyte in the water phase is a must
- the type of oil matters
- the process matters a lot! It depends on the emulsifier, but in most cases, water is to be added to the oil phase by drops under low-shear mixing, and then it should be exposed to high shear to reduce the size of droplets.
- professional chemists with access to a lab will throw rotten eggs at me, but I am saying it anyway: you don’t need a homogenizer to make a foundation (w/o, w/si). A 600W stick blender will do. An overhead stirrer is a must, though.
- if you want to invest money in something related to w/o, buy a decent microscope to see the shape of droplets. That’s a good predictor of stability in the absence of a lab to run a proper stability test.
- do not add preservatives in the end! It makes no sense, as water is an internal phase!
- PEG-10 dimethicone and ABIL WE 09 MB are amazing
- Stearyl dimethicone (as a stabiliser) = improved aesthetics (IMHO)

Similar issue here…

Best selling Asian products can be really hard to reproduce in general because they use a lot of exclusive raw materias. Many Asian companies like Shiseido, Amorepacific etc. create even their own emulsufiers, emmolients etc.

PEG-10 isostearate isn’t exclusive, but I think I can’t find ir in my country and that emulsufier has unique advantages. Which brand of that emulsifier are you using?