[Pharma]

Might work as well, it’s a base. Hydration radii are different and the % of neutralised free fatty acid will affect emulsion type but, as I said, it’s just a base like NaOH or KOH.

[Pharma]

BTW at which temperature do you measure pH? If you do measure/adjust it when the product is hot, pH will rise upon cooling.

If you’re adding it to the hot product, your preservative will diffuse into the oil phase and that’s why it fails. Adding it could (depending on the formula) will result in more preservative in the aqueous phase and hence a better preservation.

[Pharma]

Just had the time to watch it: nice! Thanks for sharing!

[Pharma]

Rice bran wax contains only small amounts of free fatty acids. Adding sodium hydroxide might still work but be careful adding not too much (control pH).

[Pharma]

So far, I’ve observed pro-oxidant activities only with ascorbic acid. The pronounced effect of ascorbic acid regarding pro-oxidative effects has probably something to do with it easily changing chemical structure upon losing two electrons whereas phenolic compounds such as tocopheryl radicals are remarkably more stable and hence might not redox cylce.

Also, pro-oxidative reactions depend on oxygen supply, available substrates, pH, and are boosted by free iron ions -> Minor changes to a formula can change it from stable to degrading or vice versa.

[Pharma]

What about using silica? Dissolve propolis in something, add it to silica and work that into the paste.

[Pharma]

What are the melting points of the two oil phases?

High amounts of wax are sometimes used to stabilise emulsions which contain no or “not enough” emulsifiers. On the other hand, the following scenario is possible: too much wax = high viscosity upon cool-down = not enough time for the emulsifiers to diffuse to the droplet-surface.

But then again, it depends on a lot of things, for example what kind of emulsion you have.

Posting your ingredients wouldn’t hurt .

[Pharma]

Doreen said:

@Pharma
…
Does Bronopol have (strong) antifungal activity then? I thought that it was mainly antibacterial?

About the lecithin that I use in some of my emulsions: do you think I could use parabens without worrying about these being inactived by the lecithin?
I use 1-3% Rovisome CE Plus (contains 10-25% lecithin) and 0.1-0.5% Phytrox LTR15-IP MB (lecithin is mentioned first in the LOI).
…

Good question regarding bronopol… I would have to look that up.

About your lecithin: I’d guess it shouldn’t pose too much of an issue as it’s present in only minor quantities. But honestly, that’s just a wild guess!

BTW why use both Rovisome and Phytrox? They’re so similar you could either include rosemary extract in the former or pentylene glycol in the latter to get about the same result.

[Pharma]

Better to take a pure anionic emulsifier and not glyceryl stearate SE which contains only about 1/10 anionics.

Assuming it really were charge related and by extrapolating from the 10% pigment which work fine: either up magnesium stearate to about 1% or add roughly 0,5% anionics because you might require more than just the 0,2% I mentioned above. On the other hand, a “permanent” anionic emulsifier (magnesium stearate is pH dependent and hence not always 100% anionic) such as a sulphate might actually work with less…

BTW did I already ask: What’s the pH before and after you add the custom blend?

If high speed increases viscosity it usually means that it’s a “real” water in silicone emulsion (high shear/speed = small droplet size). As a rule of thumbs, lamellar emulsions can be made with a lower shear force.

[Pharma]

First, replace glyceryl stearate SE with glyceryl (mono-)stearate. Common brands of glyceryl stearate SE are anionic emulsifiers and hence not very compatible with your formula.

[Pharma]

I did some thinking, some reading, some more thinking and reading…

It looks like a tough nut to crack and that’s what intrigues me though it’s hard work. See, what we learn in galenics is o/w emulsions and their laws. Hence, these come natural to me which is quite the nuisance when thinking about inverse emulsions such as w/o or w/si. That’s because half the laws don’t apply and the other half, though still following the same rules, results in completely different effects. In addition to that, you get the same effects with different approaches in the two emulsion types. On the other hand, most w/o emulsions aren’t of the droplet-type but lamellar or 3D-networks.

That said, there might be some misconceptions in my first brain churning approach, who knows? For example, removing electrolytes might shift the droplet-type emulsion to a worm-like structure which can as well result in an emulsion of higher viscosity, not the other way round.

I’ve been thinking about triple ratio of non-ionic surfactant/anionic surfactant/fatty alcohol, surface shape of these molecules, surface charge aka zeta potential etc. The one thing all comes down to seems to be charge related. Somehow the custom pigments annihilate negative surface charge although in a w/si emulsion, there is only a charged inner surface, not an outer one. Hmmm….

It might be advisable to re-start from the beginning, figuring out a simple, easy, and cheap solution:

- “Your supplier said…” does that mean you have a basic formulation you improved over time? What would the most reductionistic formula (w/o pigments) which is still stable and viscous be?

- Did you find out what’s in that custom blend? Do they use quats?

- What’s the highest amount of custom blend you can add before emulsion tips over?

- The below 40°C homogenisation, is that also low shear?

- Do you know for sure it’s a w/si emulsion?

- Don’t throw your failures away! Try for example adding an anionic high HLB emulsifier at 0,2% (guessing here), just something on your shelf such as glyceryl stearate citrate. Even an anionic detergent like SLS, SLES, an isethionate, or a lactylate might work. If they work: your issue is most likely charge related and hence solvable.

Gotta go for now (it’s getting less hot and the doggies need their party).

[Pharma]

em88 said:

Nizoral 60 ml shampoo costs like 14 Eur?  😮

That’s without the taxes (minimum ~4 Euros and up to ~10 Euros) .

It’s one of the less expensive meds we have, paracetamol 500 mg with 20 pills is probably the cheapest one for € 2,50 to 3.-, Aspirin 500 mg with 20 pills goes for € ~9.00.

Welcome to Switzerland!

[Pharma]

Yes, cera bellina is an emulsifier and so is magnesium stearate. They may not be used primarily as such but they are (co-)emulsifiers. Magnesium stearate is of special interest because it imparts a negative (inner) surface charge to the inverse micelles.

Your supplier is correct . I’m not telling you to reduce them to solve the problem but I’m proposing to completely remove them in a small batch in order to help you finding a solution. In your case, I was a bit short-worded in this regard yesterday evening, sorry! I’m expecting your base emulsion (w/o pigments) to become less viscous and not your liquid endproduct to become viscous again! This experiment would simple help you understand what’s going on with your formula and point towards a worm- or net-like structure which turns into inverse micelles. Then it would be a closer guess assuming that adding your custom blend is destroying your emulsion by changing emulsion type in a certain way. Once you know what causes the issue, finding a cure becomes way more simple.

Can’t help you today with the microscope. Have neither tried my old binocular nor the USB microscope to visualise emulsions ;( . It’s on my to do list but… but not today. It needs to be “see-through”, not just a “look on top” (lacking the sciency terms for this ). Maybe @Perry knows which magnification is needed for the everyday life of a cosmetic chemist?

Any you’re welcome! Glad I could kick-start your curiosity!

[Pharma]

Trick for not-nano zinc oxide sunscreens on babies: Use oil to soften it up and then wash away with shampoo. From a physico-chemical perspective, something like a waterproof makeup remover might work well, I’m thinking oil-to-milk cleanser.

[Pharma]

@Dtdang Use 316 for increased chemical resistance

[Pharma]

Corrigendum: Glycerol is not an electrolyte, don’t remove that one .

[Pharma]

ngarayeva001 said:

…The same formula (all other inputs are the same) where I added 10% octyldodecanol to the oilphase and 10% of dry pigments didn’t break. …
I didn’t calculate HLB as I was hoping that since I use a blend of 3 emulsifiers I should be covered.
…
To summarise my problem: I want to achieve a high viscosity foundation. The base has high viscosity without pigments. When pigments added after emulsification, the viscosity stays high but the product separates (within an hour!) when pigments are added to the oil phase, it stays together but it’s water thin.

Weird… any chance of finding out with what the custom pigments are coated?

You actually have 5 emulsifiers in your formula .

Do you have a microscope? You probably don’t have a w/si emulsion but something like a so called liquid crystal aka alpha-gel emulsion which is just on the brink of either breaking or turning into a real water drops in continuous silicon phase emulsion (something like Table 1 on PAGE 4: Lalpha, V2, or H2 turning into I2)… You don’t happen to have a good microscope or a polarised light source (which could either come with the microscope or be self-made using sunglasses).

Something you could try: Lower HLB, generally increase surfactants, remove/reduce electrolytes (betaine, glycerin, sodium lactate, and sodium PCA).

Gotta go sleepy-sleepy

[Pharma]

LoL! No, botox doesn’t corrode metal but brain cells :blush: .

The way you wrote it I was under the assumption that you probably might not know why it corrodes or think that it’s hypochlorite as is. Doesn’t really matter… I prefer hydrogen peroxide or in situ generated performic or persulfuric acid if I really have to get something clean. Although, I have to admit, the air gets somewhat unbreathable when using 30% H2O2 or performic acid.

You could try out an ozone generator. It doesn’t affect the steel work bench (it only annihilates everything else in the room, but not the steel work bench). A doctorate student made that experience… except metal things, EVERYTHING else crumbled to dust when touched! It was like in a Hollywood movie when sunlight hits a vampire. It was hilarious (for those who hadn’t their work ozonised).

[Pharma]

Don’t forget the olive wax and cetyl alcohol: The oil phase is probably solid which results in a semi-stable emulsion as for example used in traditional cold cream. This would also explain why the emulsion breaks when adding optiphen plus.

[Pharma]

@Doreen Your inactivation graph isn’t helpful: I read the book chapter and that graph stands all alone for itself, no explanation, no concentrations, no control (bronopol alone), no references… Probably, bronopol is doing the whole job and parabens were used at a too low concentration?

@chemicalmatt WIKI: not sure if they mention the cream Niosôme by Lancôme. Allegedly, l’Oreal invented niosomes and the first cream containing them was named accordingly.

Made some massage oleogel this week (for personal/immediate use, not caring about long-term preservation) using hydrogenated lecithin as co-gellant. Added a bit too much and it turned into a free standing gel (reminds me of shea butter) within 2 days. Still nice to apply and easy to spread once on the skin, no tackiness, oil lasts just long enough and leaves a nice protective film (a bit waxy but that’s likely due to the wax). True, it requires some adjustments but I’m happy with that first trial.

Regarding difficulties preserving lecithin: Apart from iron, phosphorous is the limiting nutrient/mineral for microbial growth. Phosphate is a semi-macro nutrient for microbes and usually not present at sufficient amounts. Adding lecithin, a readily available source of phosphate and nitrogen which also contains fair amounts of trace elements, creates the perfect breeding ground for microbes. This might be the reason why it’s so hard to preserve lecithin containing formulations.

[Pharma]

I’m only familiar with phytic acid in plant physiology and gardening. There are really just a few soil microbes I’m aware of which can use phytic acid. Sure, if you happen to have exactly those in your product…

Problem is that (reminds me that I need to answer another thread regarding lecithin which has the same issue), besides iron, phosphate is THE limiting nutrient/mineral for microbial growth. Only a very few ingredients contain phosphorous; Lecithin and phytic acid as organophosphate and some phosphonate detergents (IIRC usually high pH laundry detergents) but these are even harder to degrade. Apart from that, it’s only present in some plant extracts and claim ingredients such as ATP and DNA. The extra amount of available phosphate is probably the reason why lecithin containing formulations are a PITA to preserve. Theoretically, phytic acid with its 6 phosphate groups could be a real superfood for microbes but as I said, it’s not readily degraded (in soil, that is).

Back to your salicylic acid: How much iron do you guess are in your toner? 10 ppm as contaminants? 2% minus 10ppm = 2%. Question: what’s the difference between 10 ppm iron-salicylic acid complexes and 10 ppm iron-gluconic acid complexes?

Out of curiosity, what’s in your formulation that requires addition of a chelate?

[Pharma]

@Doreen It’s chlorine which causes rusting .

Me, I prefer using stainless steel and get new stuff if necessary. Plastic is often not very practical for the reasons you mentioned. Wood on the other hand is more of a one time usage thing, terrible to really clean.

[Pharma]

It’s the same and then again it’s not. Glyceryl caprylate does refer to monocaprylate as well as tricaprylate or mixtures of mono-, di-, and tricaprylate. In chemical nomenclature, it refers to the triglyceride i.e. tricaprylate whereas in cosmetics it stands for monocaprylate aka GMCY. Why it is frowned upon, I do not know nor have any idea why this could possibly be. I haven’t even heard so before but then again, what isn’t frowned upon?

True, it’s not exactly natural although it does exist in nature (your body contains traces of it!) but it’s synthesised either by simple thermal, catalysed (acid or base) or enzymatic esterification. These are all eco-friendly and use glycerol and caprylic acid, both for example derived from coconut oil. The small quantities of added acid or base is either sulphuric acid or potassium carbonate (recyclable or reusable as fertiliser) and the enzymes come from microbes. Nothing dangerous about it, fully and quickly biodegradable, no off-target effects, it’s even digestible (sure, too much caprylic acid might result in mild diarrhoea 🙂 ).

[Pharma]

Thanks, I stand corrected, not antibiotic (yes, the word antibiotic or rather it’s origin is not coherent with modern definition) but a fungicide. Although, that doesn’t change a thing. It is suspected that the use of natamycin causes cross-resistance with similar fungicides.

[Pharma]

Ascorbyl phosphate is not oxidising and hence, no corrosion/discolouration of your spatula.

We learn that too but there’s not a really good answer why. Trace amounts of iron and other heavy metals of the alloy might be freed but that’s so small traces that adding an unrefined plant oil to your cream would be a dangerous endeavour . The staining/spots though is not aesthetic and can even cause rusting.