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Separation of Colors in Nail Polish
Hi! I’m an undergraduate student of Chemical Engineering from Puerto Rico. I’m doing an internship with a cosmetic company about nail polishes. Especially in how to avoid or minimize the time that nail polish begin to separate, they already export products to Miami, US but some nail polish especially the lights colors, blues and purples arrive separated, I don’t have problem with the dark ones (red, black, etc). This happen also in our storage but take a little more time to separate.
I hope you can help me with some suggestions because here there is not another engineer or chemist, this is because the company don’t manufacture the product, they buy the product in United States and are in charge of packaging in the small bottles but before that they mix the pail of nail polish.
Some operational variables that I’m going to study: type of mixer (blades), time and rate of mixing, and packaging material
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9 Replies
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When painting cars with metalflake in acrylic, it is necessary to agitate the sprayer container in order to avoid settling-out. I guess that’s what is happening. Probably you’ll need a suspension agent but that is way beyond me.
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solvent-based nail polishes typically contain quaternised bentonite/hectorite clays as suspending agents, e.g. Bentone 27V CG from Elementis (INCI: stearalkonium hectorite)
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I’ve worked with nail polish and nail polish formulation, so I can help a bit.
First off, all nail polish is colored with insoluble pigment, for a variety of reasons (not the least of which is that customers get upset if their nails are dyed even after they remove the nail polish).What this means for you and the company you are working with is that all of your products are dispersions/suspensions - and the reason you are getting “separation” is that gravity works. The good news is that there are established rules that govern the behavior of dispersions.The rate of settling that you’re going to get will change based on only two or maybe three variables. I’m not going to get into the rheology much, but the most important variable is the suspending power of your nail polish base. The suspending power is somewhat related to the viscosity of the base, but is much more specifically related to the yield value (which, unfortunately, is much harder to measure than viscosity) Because nail polish is deliberately formulated to be thixotropic (look it up) you will have to roll or stir it for a very specific time every time you want to measure viscosity. Consult your supplier for specs and methods.The other major variable(s) will be the pigment particle size, weight, and shape. Because you’re counting on the suspending power of your base to fight against gravity, the smaller/lighter particles with as much surface area as possible will stay suspended longer.The minor variable is being able to prevent the pigments from agglomerating/re-agglomerating. -
Thank you all!
Bill_Toge: Yes, our nail polishes contain both stearalkonium bentonite and hectorite
Bobzchemist: I look up about thixotropic I thought that nail polish is a pseudoplastic. So it means nail polish is both thixotropic and pseudoplastics, its viscosity it will depends of the applied shear stress time (mixing time) and the increasing of shear stress (rpm of mixer)?The supplier says its viscosity range is 410-460 cps. The merchandise takes 10 days to arrive to our facilities. So obviously we need to mixing to re-suspend the pigments. I was thinking to do the following for my research: If I take a sample after the mixing to measure viscosity I guess it will not be between the supplier range. I can vary the time and rpm of mixing and take a measure viscosity before mixing until I have the viscosity that our supplier provides. This maybe minimize the time of settling.The company don’t have a viscometer so I need a good reason for them that spend approximately $4,000.00 it will be help to our problem.I took engineering materials course so about the yield value I know is the stress that need to be applied to make a transition between elastic deformation to plastic deformation. -
I’d talk to an automotive paint manufacturer. It’s the same stuff!
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I make a mistake in my past comment isn’t after is before.
If I take a sample after the mixing to measure viscosity I guess it will not be between the supplier range. -
You need to talk to your supplier. The ideal situation is that you and the supplier both have the identical (or at least very similar) test equipment, so that they test a shipment, send it to you, you test the shipment, and BOTH of you get similar numbers - if shipping a product causes it to fall apart, you have serious problems.
As for justifying the price of a viscometer, right now, you are at the mercy of your supplier - you have no way of telling whether or not they sent you good product.(Also, not that expensive http://gardco.com/pages/viscosity/vi/dve_viscometer.cfm)It sounds to me like you need your supplier to increase the amount of suspending agent. -
We used to use something like this to mix closed containers, so that the mixing couldn’t evaporate any solvent. But the best thing to do is still exactly what your supplier does.
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We actually use a Drum Rotator like this one:
Also we acquired recently a mixer that allow mix without open totally the drum.MMX 100 Universal Drum Mount (Closed Drum)I ask the supplier which type of mixer they use to blend the dispersed previously product, also type of blades, time and rpm of the mixer; but unfortunately they cannot provide me that information, they says is very proprietary to his business.Thank you for the suggestion!
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