Bill_Toge
Forum Replies Created
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@Chemist5000 thioglycolic acid has a molecular weight of 92 g/mol
the European legal limit is stated as %w/w thioglycolic acid; the conversion factor (130 g/mol ÷ 92 g/mol) accounts for the difference in molecular weight between the acid and its potassium salt
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personally, if I were creating a body remover, I’d use something like concentrated nitric acid, but if the police ask you any questions I said nothing
facetious remarks aside, it depends on the legal limits in the area you intend to sell it; in Europe, for instance, the maximum thioglycolate level for depilatories is 5% as thioglycolic acid (hence, the limit for potassium thioglycolate is 5% × 130 g/mol ÷ 92 g/mol = 7.06%), and the pH of the product must be between between 7.0 and 12.7
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if it’s only a layer on the surface, that suggests water loss by evaporation as the most likely cause; if it were an inherent incompatibility within the formula, you’d see it throughout the whole product
one thing that baffles me is why your product is so strongly coloured - have you added a dye to it?
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try carnauba wax
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in the lab we use a miniature coffee grinder (bought from the local supermarket for the princely sum of £10) for high-shear airtight mixing of powders - we don’t use it for colour cosmetics, though, so there’s no guarantee it’ll grind the pigments effectively
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do you have the capability to hydrogenate it?
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you could try thickening a solution of sulphuric acid with xanthan gum
it would be a gel, and besides fat, it would also burn skin, hair, bones, organic material in general, some plastics and quite a few different types of metal
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while it’s not ideal, it is at least better than having them fabricate scientific findings in order to justify political policies, which I suspect will become a common occurrence before any of us are much older
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another thing to bear in mind is that some fragrance compounds have maximum safe limits set by IFRA, which put a usage cap on fragrances containing these compounds; any reputable fragrance or essential oil supplier should be able to supply an IFRA certificate declaring the safe usage limits for particular product types
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@Mamun chances are the ascorbic acid is the culprit here; something like sodium erythorbate will do the same job with less discoloration
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in what way is it unstable?
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@MarkBroussard true, but no sensible customer would seriously encourage the contract manufacturer to overcharge them and rip them off
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it depends on what’s in the fragrances; we have some fragrances which smell incredibly strong at 0.2%, and others you can barely smell at all at 2%
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there is another way to incorporate a fragrance into a powder product: premix it with a very absorbent grade of silica (e.g. Sipernat 22 from Evonik)
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a friend of mine at another company described an occasion when one of their customers (a very expensive department store in London) wanted their product to have a longer INCI list, and cost more, because that would make it more aspirational
it was notable for being the only time a customer ever complained that their product was not expensive enough; a very old saying about fools and their money springs to mind
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@Doreen81 iron and copper are the most likely culprits; other catalytically active transition metals (manganese, platinum, palladium etc.) are typically present at such low levels, assuming they’re present at all, that they have little if any effect
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for what it’s worth, whenever we’ve been audited under ISO 22716 (the worldwide cosmetic GMP standard), the question has never been asked
as a rule we store retained samples for three years after the date of manufacture, except for customers who require them to be stored for longer, and our auditors have never had an issue with this
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further to @Doreen81’s comments about benzene formation, I might also add this reaction only happens in the presence of iron, because the iron acts as a catalyst: as a reducing agent, ascorbic acid on its own is nowhere near powerful enough to reduce benzoic acid to benzene (if it were, it would be much more hazardous, both to human health and in general)
if you use deionised water and a chelator, the concentration of iron in the product will be somewhere between undetectable and nothing at all
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instead of vitamin C and E, try adding sodium sulphite and BHT
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they are produced by reacting glucose (from corn starch) with fatty alcohols (from coconut and/or palm oil); whether or not you consider them natural depends on how you define the term ‘natural’
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also, you want to make sure you only ever stir it clockwise; if you stir it anti-clockwise you’ll induce a Coriolis effect which may affect the stability of your product
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it could also be the result of contamination
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sounds like ester hydrolysis - how much is the acid value increasing by?
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there is no simple answer to this, simply because the SPF you achieve in practise depends on how efficiently your formula acts as a filter, which in turn depends on how the product flows under shear
if you can get hold of them, try using encapsulated UV filters, as they take a few variables out of the equation and are supposedly more reliable and consistent
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the Wijs iodine test (DIN 53241-1:1995-05) will give you the degree of unsaturation, which can be used to determine oxidative stability over time
the peroxide value (determined by titration with iodide in acidic conditions) will give you an idea of rancidity - the lower the value, the better