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Pigment Dispersion in Stick
Hi all, I hope we stay safe and healthy over this tough period.
Can I have some advice on some issues I’m facing in my stick bronzer project please?
As you can see from the picture below, the black iron oxide couldn’t dispersed well in the formulation (red and yellow iron oxide are fine). even after gone through many times of roller mill. May I know what causing this issue? It is weird for me to see this as other pigments are disperse well besides this.
Here is my ingredient list for your reference:synthetic wax 4.00%
candellila wax 6.50%
microcrystalline wax 3.16%
ozokerite wax 6.00%
Floraester 60 1.00%
floraester 7 2.00%
Pentaerythrityl Tetraisostearate 6.00%
hydrogenated Polyisobutene 20.00%
Diethylhexyl Adipate 20.00%
talc 2.00%
mica 3.24%
PMMA 5.00%COSMOL 222 9.00%
BENTONE GEL 2.00%
IRON OXIDES 10.00%Hopefully can get some advice and learn from this.
Thank you so much in advance
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11 Replies
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Mysterious thing there PeiHoong. Only thing I can think of is ratio of mineral dispersives (esters) to minerals is about 2:1, a somewhat high load. I include the mica & talc with the iron oxides and do not include polyisobutene with the dispersion medium. (Not sure how good COSMOL 222 is in dispersion compared to the other 2 esters). Which Bentone Gel are you applying? There are different solvent bases in those.
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@chemicalmatt yes right?! i cant figure out as well. i tried the bentone gel disperse in silicone as well as isododecane, both same result. Can’t think of any…
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What order are you mixing your pigments in? Perhaps try the black first and ensure homogeneity before adding the red and yellow iron oxides?
Otherwise, have a look at your raw materials’ particle size/mesh. Having it closer to that of the yellow/red iron oxides might help aid dispersion. I’ve seen issues first-hand of black iron oxides trying to drop out of typically stable mixtures on account of being physically dense.
Lastly, check whether your yellows/reds include any talc or not. This will oftentimes help dispersion help keep the mixture in suspension. -
@Benz3ne The three iron oxide used is from the same grade and hence have similar particle size. The same combination is used in other formulation and all work well, only doesn’t work on this formula. Is that means that premix the iron oxide with talc will help the dispersion?
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PeiHoong said:@Benz3ne The three iron oxide used is from the same grade and hence have similar particle size. The same combination is used in other formulation and all work well, only doesn’t work on this formula. Is that means that premix the iron oxide with talc will help the dispersion?
Not necessarily but it has helped on occasion for me. I would say try it with the black iron oxide added first, mixed until homogeneous and add the yellow and red iron oxides afterwards and see what happens.
I hope you’re well and safe also.
It might be worth clarifying with your supplier about particle size. I have seen some variations from same suppliers before. If you’re milling it shouldn’t have that much impact. I’d go with my first suggestion - try the black first and then add the other pigments.
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@Benz3ne ok, i will try as per your advice then update you again on this. Really appreciated on your help.
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Hi PeiHoong
I suggest you to review the composition of oils: you should use oils with wetting pigment properties ( medium to high polar emollients). In your formula you can increase the amount of Pentaerytryl Tetraisosterate.
Another thing: It is better if you don’t use magnetic stirrer, because it attracts iron oxide and the product can change color. -
@Benz3ne i have tried as per your advice but it doenst seem to work, the black pigment still appear…T.T
@Sil Thanks for the advice, i have increase the amount of Pentaerytryl Tetraisosterate and stir without magnetic stirrer, still the black pigment appear…
I am still trouble-shooting the issue will share the progress with you if there is any.Thank you very much.
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One thing that has sprung to mind for me - are any of your pigments damp at all? Do you have a means of checking loss on drying or desiccating them?
If they’re damp then it could lead to them being more difficult to incorporate, especially if the majority of the stick mixture is oil-based.
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@Benz3ne really? but so sorry i dont have any device can help to check on this…maybe i will try to put the pigment in oven at 50C for few hours before milling them?
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PeiHoong said:@Benz3ne really? but so sorry i dont have any device can help to check on this…maybe i will try to put the pigment in oven at 50C for few hours before milling them?
You can do it without much equipment. Desiccators are inexpensive but otherwise yes, weigh first, then oven with open front at 50°C for a few hours, then weigh again. More resolution in weighing is better as gives more detail.
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