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Crystals in the SPF 50 Cream
Hello fellow formulators,
I hope this message finds you well. I’m a formulator currently working on an SPF 50 cream, and I’ve encountered a specific issue with the formulation. Here is the composition:
<google-sheets-html-origin></google-sheets-html-origin>PARAFFINUM LIQUIDUM 2%
CEYL ALCOHOL 2.80%
GLYCERYL STEARATE 2%
STEARIC ACID 4.00%
CETEARETH 25 2.5%
CETEARYL ALCOHOL 1%
COCOS NUCIFERA OIL 0.50%
Polawax (Cetearyl Alcohol and Polysorbate 60) 0.50%
BUTYROSPERMUM PARKII BUTTER 0.20%
PRUNUS AMYGDALUS DULCIS OIL 0.40%
ARGANIA SPINOSA KERNEL OIL 0.40%
ETHYLHEXYL METHOXYCINNAMATE 8%
ETHYLHEXYL SALICYLATE 3.80%
BUTYL METHOXYDIBENZOYLMETHANE 5%
OCTOCRYLENE 4.90%
DIMETHICONE 0.50%
GLYCERIN 3%
WATER 40.63%
TETRASODIUM EDTA 0.20%
UREA 3%
PROPYLENE GLYCOL 1%
ALLANTOIN 1%
AQUA 5%
PHENYLBENZIMIDAZOLE SULFONIC ACID 5.00%
SODIUM HYDROXIDE 0.87%
ISOPENTYLDIOL1%
Phenoxyethanol (and) Caprylyl Glycol (and) Chlorphenesin 0,8%
I’ve observed the formation of white crystals occurring after the cooling phase in the manufacturing process. Notably, the emulsifiers were adequately heated, and all materials were fully melted. Additionally, the pH level falls between 5,5 and 6
Despite these precautions, the issue persists. I am seeking specific guidance from the community on the nature and origin of these white crystals, as well as effective strategies to resolve the problem. Your insights on the potential causes and solutions would be invaluable.
If anyone has faced a similar challenge or can provide detailed advice on crystal identification, root cause analysis, or formulation adjustments, I would greatly appreciate your input.
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13 Replies
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Make élimination test : with making basic sample (sample without any white powders that you have) then divide your sample to samples “the number of white powders you have” . Then add to each sample just one type of powder and watch which powder causes that.
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Thank you very much for your response. However, for the elimination tests, I cannot perform them at the laboratory level. This is because, by chance and without any explanation, we obtain crystals in the industrial batches (100 Kg). For small samples of 100 grams, we do not obtain crystals
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I suggest to make 1 kg sample then if you don’t find the problem I will go for that the cause is changing process from small sample to industrial one.
Changing process ( temperature, pressure,type of stiring, speed of stiring, order of adding ingredients…)
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UV Filters thoroughly dissolved in emollients to prevent crystallization. With such high concentrations of filters as you have, you need to add a lot of emollient, preferably a light one: Isoamyl laurate, Coco-Caprylate/Caprate, Caprylic/Capric Triglyceride. It is best to use at least about 10-15% and heat the filters in it until it is fully dissolved, and only then combine it with the rest of the fat phase.
Regards
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Thank you very much for your response. In fact, the crystals we obtain resemble pieces of glass. We have encountered the same issue with crystal formation in a moisturizing cream formula with the following composition:
Cetyl alcohol 2.8%
Glycerol stearate 1.5%
Stearic acid 1.8%
Ceteareth 20 2%
Cytostearylic alcohol 0.5%
Shea butter 1.5%
Coconut Oil 1.5%
Almond oil 4.5%
Argan oil 0.5%
Glycerine 3%
Propylene glycol 3%
Allantoin 1%
Water 75.7%
SALIGUARDCOS 0.7%
That’s why I find it challenging to identify the origin of the crystals. Is it the filters or other ingredients that are causing this issue?
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In fact, in such a case, the allantoin concentration may also crystallize. Do you dissolve it hot in the water phase?
We probably did not manage to make a stable recipe with an amount of more than 0.6% of allantoin, otherwise it crystallized in the refrigerator stability tests.
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I’d actually increase Octocrylene and reduce other UVB crystalline filter. Also, how are you adding your allantoin? That’s a high level (I wouldn’t add it myself in this kind of formula). If you add it in the cool down phase and the product is already thick, that can be a reason for those crystals.
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I think allantoin could be a potential crystallizer here, but also the PBSA. I haven’t worked with it commercially but I believe product pH needs to be right around neutral for PBSA to remain soluble.
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I’m sorry, but what does PBSA mean?
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I did know it before just a little bit of thinking ????: PHENYLBENZIMIDAZOLE SULFONIC ACID
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Yes, that’s right, the PHENYLBENZIMIDAZOLE SULFONIC ACID (PBSA for short) recipe should have a pH of approximately 6.8-7.1, below that it may crystallize
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Try reducing your Allantoin to less than 0.5%. This is an ingredient that is known for crystallization at high concentrations. You could try searching the forum for more information.
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Is there a possibility that the emulsifiers we used could react with other ingredients to form crystals?
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