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Homogenizers
Hello,
I’ve been browsing for homogenizers for my home brewed cosmetics, for own (and family) use, so no need for special/expensive equipment.I’ve come to the conclusion I might just as well use the stick blenders we already have (one of them I can keep for cosmetic use only). Point is, these are for large(r) quantities. Not for a ‘batch’ of 100 ml for example and I can’t find tiny ones for sale.
It’s not a problem if I have to make larger batches even if I need less, provided that I don’t use expensive ingredients that need to be mixed.
Like hyaluronic acid, glucosamine, ferulic acid. These ingredients are about 10 dollars per gram here, so I can’t afford the inevitable loss by using (large) blenders etc.Does hyaluronic acid for example absolutely need to be sifted, and mixed by a homogenizer? Or can it be done by hand?
And what type of emulsions do absolutely require a homogenizer? For example, the ones with high oil concentrations, or depending on type of emulsifier, additions etc.Many thanks again!
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21 Replies
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Depends of your surfactant system. If it decreases a
lot the interfacial tension between your oil and aqueous phase (below 10mN.m-1)
you can form your emulsion almost spontaneously.In case of concentrated emulsions you can also emulsify by
low energy method by stepwise addition of your oil phase to water (O/W emulsion)
like a mayonnaise.by this method and choosing the good surfactant system you
can reach almost 99% of dispersed phase in your emulsion if you want.With ethoxylated surfactants you can play with
temperature and prepare emulsion by phase inversion temperature. In this case
you need only weak agitation. This method takes advantage of the change of
curvature of your surfactant with TºC so you can pass from W/O to O/W emulsion
by simple cooling or heating.All these technique need some phase behavior study of
your surfactant system with oil and water. -
“Does hyaluronic acid for example absolutely need to be sifted, and mixed by a homogenizer? Or can it be done by hand?”
It is best NOT to homogenize hyaluronic acid - or any polymeric or high molecular weight material. Aggressive treatment as induced by the high shear forces encountered during this type of processing often results in degradation of the material.
A better way of dissolving these materials is to first of all mix into a water miscible non-solvent (ethanol, a glycol or such) then add the required water with (low shear) stirring.
I’ve been in this game a long, long while and the only times I needed a homogenizer I could count on the fingers of one hand. As I said in another thread, judicious formulation can, more often than not, avoid the need for high shear mixing.
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If you find you absolutely must homogenize, you can do so on a small scale manually using these:
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@jeremien, @johnb, @Bobzchemist,
thanks for your suggestions.I think I’m a little lost in translation on the mixing equipment.
Is a homogenizer comparable to a rotor-stator mixer for example?
Or can the word ‘homogenizer’ be used as a general name for any mixing tool? -
Is it a good idea to mix the hyaluronic with for example glycerin or propylene glycol, to make a slurry, but by hand? Does it then fully hydrate if I put it away for a few hours?
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in this industry, homogeniser = high-speed rotor/stator mixer
also, if you put anything a slurry it shouldn’t hydrate at all; the idea of a slurry is that you add it to water, so that the slurried substance disperses slowly, allowing it to hydrate uniformly, and (hopefully) without lumps
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@Bill_Toge, clear now, thanks!
Indeed I didn’t state the slurry sentence exact enough. Make a slurry with glycerin or propylene glycol for example, put it in the needed amount of water and then leave it for a few hours.
And exactly: hopefully without lumps. Would mixing it (slurry in water) by a small kitchen blender give less risk of lumps than by hand? -
You must stir your slurry but this can be done in a gently manner, not with the molecule ripping high forces introduced by a homogenizer.
Ensure there are no lumps in your slurry before you add the water.
Full dispersion may take a few hours to complete but there is no need to stir for all of this time. Once the mixture begins to thicken, stirring can be reduced in frequency.
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I agree with Bill, we tend to use “homogenizer” as a general term to talk about rotor/stator mixers.
This causes confusion because other industries/fields use the term differently.
In dairy processing, for example, a homogenizer is a high-pressure mixer used to emulsify milk fat into milk, and is completely unsuitable for cosmetics.
In biology, homogenizer is used as shorthand for a “tissue homogenizer”, which aren’t quite the same thing as the homogenizer/mixers we talk about here as homogenizers. This, I think, causes the most confusion, particularly among beginners.
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If I had to make 100ml batches, I think I’d try using these:
https://www.amazon.com/100ml-3-4oz-Plastic-Micro-Centrifuge/dp/B00N3YIEI0/ref=sr_1_4?ie=UTF8&qid=1485966166&sr=8-4&keywords=100ml+centrifuge+tubewith one of these:
https://www.amazon.com/LabGenius-MI0101001-Mini-Vortex-Mixer-Clear/dp/B01CLLBZ6S/ref=sr_1_1?ie=UTF8&qid=1485966224&sr=8-1&keywords=test+tube+mixer -
@Bobzchemist High-pressure homogenizer unsuitable in cosmetic; except if
you want to prepare nano-emulsions -
@jeremien, you’re right, I probably should have clarified - the high pressure homogenizers used for dairy products (Gaulin, Crepaco, etc.) are almost always unsuitable for cosmetics due to their inability to handle viscosities much higher than water. Nano-emulsions, if they’re thin enough, might be an exception.
There are high-pressure homogenizers (Microfluidizers, etc.) that are specifically designed for cosmetics and higher viscosity fluids.
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I’ve been in this game a long, long while and the only times I needed a homogenizer I could count on the fingers of one hand.
@johnb, By this alone I know that I really won’t need one. At work we’ve used Ultra Turrax, two types. The large one mostly for making suspensions at rather low speed. The max of that thing was bizarre, it made me wonder what type of preparation would really need that.
But the substances we used mostly, even a bit of shaking would have been a ‘molecule ripping force’. (Monoclonal antibodies) Thank you for making it very clear how I should process hyaluronic acid, I’ve never worked with this ingredient before.Thank you, @Bobzchemist, @jeremien.
I’m waiting for a few more ingredients from another supplier to get started. I’ll let you know how it worked out. Thanks for the tips about emulsifiers and where to buy small homogenizers.@jeremien,
With ethoxylated surfactants you can play with temperature and prepare emulsion by phase inversion temperature.To this thread an off topic question, maybe I should start a new one, not sure. About ethoxylated surfactants: I read a preservative like phenoxyethanol can be made ineffective by these. Do you know in what percentage? Like if I use only 3% (polysorbate 80) in a formula and preserve it with phenoxyethanol (and sorbic acid), how ‘harmful’ would it be on its effectiveness?
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A development lab I moved to after a change in employment was equipped with several Ultra Turrax machines of various sizes as my predecessor had a strange idea that they were necessary to form even the most basic of emulsions. I’m sure the machines are very good at what they do but, what is that?
I worked in that lab for four years. The Ultra Turrax’s just sat on a bench completely unused and unloved.
I have to say, though, that the Ultra Turrax manucturer, IKA, makes excellent quality (but expensive) laboratory equipment and all the propeller stirrers/magnetic stirrers in that company were from IKA.
Regarding your preservative query. It is good practise, or even necessary to test the effectiveness of all new preservation systems. It is easily possible that a complicated mixture like a cosmetic product will demonstrate unexpected behaviour at any point. Many preservatives can be rendered ineffective by ethoxylated surfactants.
With phenoxyethanol, remember that it is also an ethoxylate (produced by the ethoxylation of phenol).
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In my experience, in some (not all) emulsion systems, there’s a spectrum of emulsifier levels:
Not enough emulsifier for stability>just enough emulsifier for stability if the emulsion is homogenized>enough emulsifier for stability no matter how the emulsion is made>more emulsifier than you need (possibly irritating).
If formula cost or non-irritating is a big issue, AND you have homogenizers in your production facility, it may be worth the time and effort to find that “sweet spot” of just enough emulsifier - but those cases have been rare, in my experience.
On the other hand, pigmented emulsions absolutely require homogenizers and/or colloid mills for stability - but it’s not because the emulsion needs it, it’s because the pigments need to be uniformly suspended as the emulsion is developed, or you’ll have stability issues.
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@johnb,
Many preservatives can be rendered ineffective by ethoxylated surfactants.Is this the case with parabens aswell? (These are the only preservatives I have actually some experience with.) I’m really getting fed up by the anti-paraben hype, I can hardly get them here. Same with aluminum salts for anti-transpirants, except for alum for some reason, since some people here think it’s ‘natural’ and therefore, better.
If I do decide to start a small company in skincare, this is what worries me most. The stubbornness of the easily scared and often willingly ill-informed majority of custumers.So, since it’s still for my own use, I will stick to parabens. Which preservatives do you prefer, in general?
@Bobzchemist
If formula cost or non-irritating is a big issue, AND you have homogenizers in your production facility, it may be worth the time and effort to find that “sweet spot” of just enough emulsifier - but those cases have been rare, in my experience.I think I tried that too, to have just enough. If I add something to my cream, it easily separates. If I do this with a bought cream, It looks like I can add almost as much as I like. I have one now, which I would like to use as a cream base, it contains at least five emulsifying ingredients (that are labeled solely as emulsifier). Very basic, silicone based and the only additons are aloe vera and allantoin. It appears to have an excess of emulsifiers.
My husband immediately notices the difference, if I make a moisturizer/after shave cream from scratch (water, emulsifier, oil etc.) or use a bought cream and add additives, the same active ingredients I use in my own cream. Using the bought cream as a base causes irritation, even if the only irritants on the LOI are the emulsifiers… (no fragrance, no essentail oils, no ethanol etc.)
Apart from lanolin and some surfactants like SLS, I didn’t even know emulsifiers could act as irritants. As a newbie, I’ve got a tremendous amount to learn…(And I’ve tried an HLB calculator. I wonder if it’s of any use to me if I only use vegetable oils, which are all about 7?)
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Parabens do tend to be inactivated by nonionic surfactants but, each situation should be checked for that effect. I have use a parabens/phenoxyethanol blend for a long time and found it very effective but then there was one formulation where it just didn’t work. I don’t know why, it was just “one of those things.”
I don’t do formulation work any longer. I am retired and physically disabled which makes things somewhat difficult.
So what do (did) I use as preservatives? Well, the blend I just described (Phenonip) either bought in or made up myself or any other material that fitted my ideas at the time. What I would NEVER use is any of the thiazolones (Kathon). It was known at launch (1978 (ish)) that these things were skin sensitisers yet Rohm & Haas persisted in persuading worldwide regulators that the stuff was safe. Even now, thiazolones are seen to be benign in some quarters and do not get even a small fraction of the publicity that is heaped on parabens.
Having said I don’t do formulation work now, that’s not quite true. I do get assistance in doing some practical work for me on some small molecule topical pharmaceutical products I am developing. These have a high content of glycols which makes them self-preserving.
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Stator/rotor homogenizers, allow to decrease the droplet size and decrease polidispersity, two parameters very important for stability. As many cosmetic formulas contain polymer to give viscosity to the continuous phase, most of the time you don t care about your emulsion droplet size distribution.
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@johnb, I started a new thread about preservatives because I no longer have questions about homogenizers.
About the small molecule topical pharmaceutical products you’re developing. You’ve got my attention! I’m wondering what kind of products these will be since you explicitly mention small molecules. Do you mind telling me for what kind of indications these are used? Skin diseases or also for systemic use? -
My “small molecules” comply with the accepted definiton on molecular biology of being a low molecular weight (<900 daltons) organic compound. That is to say compounds with a known and defined chemical structure and specifically excludes proteins and derivatives, MABs, etc.
They are for topical use. I have no intention of extending to other routes of administration.
Part of my development includes a novel excipient.
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I use this. Super fast, two speeds, easy to clean. 200g is the sweet spot. https://www.kitchenaid.com/shop/-%5BKFC3516CU%5D-5868596/KFC3516CU/
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