[Bill_Toge]

hydroxypropyl methylcellulose is a good thickener for this type of system, as it’s compatible with most surfactants, boosts foam and gives a long-flow, far less gooey rheology than xanthan gum or guar gum; it’s available from Univar (as various grades of Methocel) and IMCD (as Benecel HPMC)

gellan gum is excellent for suspending particles, but it will give you no viscosity whatsoever

(incidentally, Matrix Chemie and Surfachem/Birchwood Chemicals are the respective UK small-order suppliers for 3V Sigma and Evonik Goldschmidt)

[Bill_Toge]

it is possible to emulsify water into oil, but:

a) it will radically alter the look and feel of your product;

b) to get your water phase in and keep it in, you’ll need good temperature control and a very efficient shear mixer;

and c) because your PVP will be in the dispersed phase rather than the continuous phase, it will not be effective

to get a fixative, “sticky” effect similar to PVP in an oil-based formula, I’d suggest you replace part of your petrolatum (say, 10-20% w/w) with microcrystalline wax and fine tune it from there

[Bill_Toge]

@braveheart, Dissolvine GL 38 and 47 are distributed in the UK by Brenntag

[Bill_Toge]

can’t comment on that particular product, but at my last place we used to make an anhydrous zinc and castor cream that sounds very similar to it

if memory serves, it was about 15% zinc oxide (pigment grade), 5% castor oil, 4% lanolin, and petrolatum to 100%; I remember it was a hot-fill product, and an absolute pig to clean out 

it was intended to be used a barrier cream for babies’ bottoms, so its SPF was never tested

[Bill_Toge]

the pKa (equivalence point) of bromic acid is -2, so you’d have to get the pH a lot lower than 4 or 5 to form any substantial quantity of bromic acid

[Bill_Toge]

both camel and cow urine are outside the scope of the EU cosmetic regulations

as it stands, they don’t even have registered INCI names, never mind any toxicology data to prove that they’re safe for human use

because of that, no safety assessor in their right mind would approve anything containing them; and you wouldn’t able to sell them legally without a safety assessment

[Bill_Toge]

in my experience, pH meters are notoriously unreliable in solvents other than water; the lower conductivity of the medium, hence the lower current, results in loss of precision and greater variation in readings

the most common way to resolve this is to add a fixed reference electrode to your pH meter

[Bill_Toge]

@MarkBroussard and anyone else interested, Schülke & Mayr have a sales office and a warehouse in the UK, and in my experience they are very flexible when it comes to order quantities

[Bill_Toge]

if you want thorough, scientific and commercially/politically impartial reviews of contentious ingredients free of charge, the European SCCS (Scientific Committee for Consumer Safety) is a good source:

http://ec.europa.eu/health/scientific_committees/consumer_safety/opinions/index_en.htm

[Bill_Toge]

what materials are in this gel, and what levels are they included at?

[Bill_Toge]

if you want challenge tests or TVCs, MelBec Microbiology, based in Lancashire (http://www.melbecmicrobiology.co.uk/) charge reasonable rates and have a prompt turnaround time

for safety assessments, Edmund Fowles at http://www.efchemicalconsulting.co.uk/ has the relevant expertise, and takes a common sense approach (many of the big-name companies can be very anal and pedantic)

@nasrins, @braveheart, a micro lab is a huge investment to make, particularly for a small company; not only is the equipment incredibly expensive, but you also need to be able to isolate it totally from the rest of the site, and recruit qualified staff to run it

I work for a small manufacturer based in a pre-WW2 industrial unit with 22 permanent staff, and we send all our TVC and challenge samples to external labs, simply because the time, effort and money required to run an adequately functional micro lab on site would would far exceed the cost of sending the samples to to be processed by a dedicated ISO 17025 accredited laboratory

[Bill_Toge]

what kind of testing do you want?

[Bill_Toge]

in which case, you can find all the denatured alcohol formulas that are authorised for use in lotions and creams in 27 CFR part 21, subsection D

[Bill_Toge]

about time too

if I had £1 for every time we’ve had to explain to prospective customers that they can’t legally claim their product is “chemical free” unless they want to try selling an empty pack, I’d have been on the cover of Forbes magazine by now

[Bill_Toge]

@Zink, which country/geographic region is your product intended to be marketed in?

[Bill_Toge]

how much is there in the formula, and how are you adding it?

[Bill_Toge]

@Belassi a word of warning, polysorbate 80 is likely to knacker your preservatives; this is why it’s an essential part of many microbiological neutralising broths!

[Bill_Toge]

@nasrins, it would take a very powerful reducing agent to reduce benzoic acid to benzene without assistance from a catalyst; ascorbic acid on its own is simply not that powerful

[Bill_Toge]

IFSCC monograph no. 2 (“Fundamentals of Stability Testing”) covers this subject as well; like the PCPC, the IFSCC charges for copies

[Bill_Toge]

in my experience ethylhexylglycerin works well in combination with small amounts of other preservatives, as does caprylyl glycol

1,2-hexanediol (Hydrolite 6 from Symrise, or SymDiol 68 as a blend with caprylyl glycol) is supposed to be effective as well, but I’ve not used it myself

the only possible points of contention that immediately spring to mind are how they taste (I’ve not tried using them in oral care, so I can’t comment on this), and whether or not there’s enough toxicity data to support their use in oral care; if memory serves, I believe SymDiol 68 has been used in mouthwashes, but I can’t comment on the others

also, they are expensive compared to sodium methyl paraben

[Bill_Toge]

the key phrase in that paper is “metal catalyzed” - the reaction won’t happen unless there’s iron present

if you use deionised water (which, as far as I know, many food manufacturers don’t), the concentration of iron and other metals is virtually nil, as is the probability of this reaction occurring

[Bill_Toge]

@David, cosmetic grades of TEA are manufactured with the restrictions of Annex III/62 in mind; as long as the spec meets the legal requirements, and individual batches conform to the spec, there should be no issue in using TEA

[Bill_Toge]

do they actually work in one minute, or do they just claim to work in one minute?

[Bill_Toge]

if you want a preservative that’s universally approved, safe to use, doesn’t have a noticeable taste, and is effective over a broad pH range, then sodium methyl paraben is your best bet

propylene glycol works well as a preservative booster, particularly if it’s included at 5-10%

sodium benzoate is only effective below pH 5, and while you might get away with a pH that low in a mouthwash (since it only has transient contact with the teeth), a toothpaste or any other product intended for prolonged/intimate contact would very likely erode the teeth if it were that acidic

[Bill_Toge]

https://chemistscorner.com/cosmeticsciencetalk/discussion/comment/3340#Comment_3340

the only amines that can form stable N-nitrosamines are secondary amines, and even then they can only form them if there’s a source of nitrosonium ions present (sodium nitrite, or bronopol)

nitrosamines formed from primary amines will dehydrate to form diazonium ions, while tertiary amines (e.g. TEA) can’t form them in the first place as there are no free coordination sites

if you want a reaction mechanism, look up “diazotisation of amines”