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Immersion blenders for emulsion formulation: How to avoid air bubbles?
edited February 2014
Any tips on this? Immersion blenders seem fit for the task with typically 30000 rpm and sharp blades, but they're not designed to avoid air bubbles as far as I know.
Member, PCF student
Try under vacuum?
Robert Zonis, Sr. Formulation Chemist, Beaumont Products "All opinions and comments expressed are my own, have no relation to Beaumont Products, are fully copyrighted, and may not be used without written permission."
That would work, but I was more thinking something about blade geometry.
The quickest solution is to try an "Inline Speed Regulator Switch". Go to link:
This will give you speed range variable control similar to an overhead mixer dial. Many immersion blenders only have two speed controls. These blenders were made for the kitchen and not for mixing cosmetics.
> but I was more thinking something about blade geometry
You can modify the impeller/blade by twisting it at an angle (in the direction that the blade spins) or just angle in the vertical. So that it slaps the emulsion instead of slicing into it.
Also, if you are using Xanthan Gum the traditional way, i.e. dispersed in warm/hot water before adding to water phase or cold phase, stay within 0.100% range. Shear mixers do a better job at rupturing Xanthan Gum particles.
To use Xanthan Gum successfully, it has to be dissolved 100% and I do mean dissolved. It took me one week in the lab to develop a method.
I have indeed tested a inline speed regulator and it works fine with staff mixers, but not at all with brushed Dremels (just FYI).
People seem to say that you need to limit slicing force*time or you could render the emollient ineffective, but haven't seen any data on it. I guess I'll just experiment and see what works, getting some SS sheet metal and a RC boat propeller shaft (which conveniently will clamp in place anything with a hole in it).
Not a big fan of Xanthan btw, make emulsions leave residue for longer.
Member, Professional formulator
edited February 2014
Boat propellers lack the ability to produce much shear forces in the liquid, which are necessary to create small particles and therefore stable emulsions. You could compensate by using a high rotational speed to create turbulence, but this comes at the cost of incorporating air to the mix. Saw-tooth disk impellers are better because they can transfer the power to the liquid as shear force with little pumping so perhaps you could try one of those attachments from Indco or IKA. Some pumping action is needed, though, to get everything mixed. Industrial equipment usually has a mixing system and a saw-tooth impeller (or a series of) for making emulsions.
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Member, Professional Chemist
An inline speed regulator will not work with a solid state mixer. Believe me I once saw someone try one with an Arde Barrinco drop-in homogenizer with disasterous results.
Saw Tooth impellers will give you some shear, but remember sometimes you have to mix without shear. For example after you have neutralized a carbomer, high shear will tear it up.
Microformulation Cosmetic Consulting provides Custom Formulations for both large Commercial accounts as well as smaller entrepreneurs. We can provide Naturally compliant Formulations under the NSF, NPA, Whole Foods and USDA Organic Certifications. BS.Pharm Albany College of Pharmacy, Union University.
edited February 2014
Normal blenders and immersion blenders seem to work quite well to shear things up without creating too much air, I'll do some experiments with the boat prop
but I suspect as you say there'll be too much pump+air and too little shear.
a simple sheet metal blade like this \_____|_____
\ would probably work decently? Guess you just have to experiment.
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