[LuisJavier]

Welcome. On second thoughts, I usually don’t go light on menthol, but I think even 0.1% could possibly be felt on the skin.

[LuisJavier]

Menthol at 1.5% is usually a maximum for a balm if you don’t want it to be too irritating. I think 0.5-1% is ok. 

[LuisJavier]

@Pharma what is the LogP range for chemicals being permeable to the skin? Would something like acetic acid not be absorbed into the skin if left in a 5% solution, for example, on the scalp? 

[LuisJavier]

@seaberry very interesting; I had a read of some of the pdf. I imagine that during PET, it is not only E.coli count that is tested for The category of gram-negative bacteria, although I suspect potassium sorbate may be effective on more than just this species of gram-negative bacteria. 

Also, I had no clue that monolaurin was so effective too. I am interested in buying some monolaurin but have not found a source for it in the UK just yet. I was aware that coconut oil typically applied as a deodorant may have weak activity against some bacteria, likely due to the trilaurin. I suspect monolaurin or lauric acid are even more active in this regard due to having less of the glycerol molecules attached. 

[LuisJavier]

@seaberry I had no clue potassium sorbate had any effect on gram-negative bacteria. 

[LuisJavier]

@seaberry if gram-negative bacteria is already dealt with by using phenoxyethanol, then I find it redundant to use it, unless it could result in using less phenoxyethanol or if it’s more effective on different gram-negative bacteria species than the ones that phenoxyethanol eliminates. 

The following link may be useful here: https://makingskincare.com/preservatives/

[LuisJavier]

@JOJO91343 why would you use both sodium benzoate and potassium sorbate instead of just sodium benzoate when they both are used against mould and gram-positive bacteria? 

[LuisJavier]

Thank you for your comments. 

I have 4 more questions: 

1. Aside from parabens and formaldehyde releasers and caprylhydroxamic acid, are there other cosmetic preservatives effective against gram-negative bacteria (much the way phenoxyethanol is)? 

2. If I am to use sodium benzoate to preserve my product against gram-positive bacteria and mould, what pH is the best recommendation for use on the skin (in this case, the scalp)? 

3. What percentage of sodium benzoate is suggested? I’m aware that 0.5% of benzoic acid present in the final product is the maximum allowable amount, but this may be excessive for the preservation I am after? 

4. Would a combination of phenoxyethanol and phenyl ethyl alcohol or phenyl propyl alcohol really provide broad-spectrum preservation? I am skeptical about using ethylhexylglycerin due to reports of irritation (already a problem with phenoxyethanol, not desiring to exacerbate the potential issue further and the reason for which I inquire about an alternative preservative to phenoxyethanol). 

Thank you! 

[LuisJavier]

Is it possible to have a milky coloured solution of essential oils and water with additives, whilst being relatively sure that a separation won’t occur for over a year? 

[LuisJavier]

@EVchem. Great! I only aim to make it about as thick as sunflower oil so I imagine I would use between 0.1-0.5% of aerosil 200. I’m curious if there are any alternatives without contributing an oily feeling. 

[LuisJavier]

Kaolin is definitely the suspect for me in this ingredient list. Maybe the fragrance would adsorb to the kaolin and be “trapped” and altered by it. 

[LuisJavier]

@natiyo123 seems like the patent shows propanediol (1,3 propylene glycol) utilised instead of propylene glycol (1,2 PG). I’m aware that people report no irritation using propanediol, though this is a considerably more expensive ingredient.

[LuisJavier]

@chemicalmatt ah I really hoped I could have used another solvent besides MPG that is cheap and avoids the problem of irritation. Besides glycols, I wonder what that may be. Yes, I’ve tested sodium stearate quite a bit and it’s gelling ability at even low concentrations is impressive. I buy mine from mistral; I don’t know what you think about their quality. Is there an alternative to Cocoamide DEA as I’ve read that there are safety concerns regarding this one or the MEA type and what do you mean by propel-repel? 

 

[LuisJavier]

@natiyo123 I’d appreciate another recommendation as the gellant or solvent though I was initially looking for the name of another solvent I can use that will not cause irritation/rashes like MPG (monopropylene glycol) can. My concern over using a high concentration of glycerin is a sticky feel. I’d prefer to make an at least partially water-based solid stick deodorant. 

[LuisJavier]

@letsalcido One reason for a preference on glycerin over MPG specifically (not DPG) is due to the lack of skin irritation. I’m aware that high concentrations of MPG in a stick deodorant can possibly result in rashes on the underarms of some individuals, unless it’s another ingredient or a combination (which I doubt). 

[LuisJavier]

Maybe glycerin works, I can try it. Hopefully it doesn’t feel too sticky upon application. Still looking for another alternative however. 

[LuisJavier]

PeaceLoveNaturals said:

@LuisJavier So whats the funky smell in Geogard ECT? INCI: Benzyl Alcohol & Salicylic Acid & Glycerin & Sorbic Acid

I really believe it is due to the addition of benzyl alcohol because it often contains impurities such as benzaldehyde. Also, even if you buy very pure benzyl alcohol, it can oxide over time to give a strong marzipan/almondy scent. 

[LuisJavier]

If you don’t want the smell of benzaldehyde in your product, you could buy a purer grade of benzyl alcohol and use chemicals to slow its oxidation in the final product, but I think it’s best to use other preservatives. 

[LuisJavier]

Think Pharma is right, benzaldehyde smells like marzipan/sugary paste with that almond touch, whereas pure benzyl alcohol would probably smell a little bit more floral since it is found in some essential oils such as those of jasmine. 

[LuisJavier]

I’m looking at alternatives because I aim to possibly use Ultrez 30 and I wish to use a moderate pH of 6 as well as not wanting to compromise benzoic acid and it’s ester or sorbic acid and ester’s low pH efficacy requirement. Alternatively, I’m aware that I could use dispatch phosphate for thickening but at a much higher inclusion rate. Big difference in price? I don’t know. Sensorial upgrade? I don’t know again.
I’m not keen on benzyl alcohol but I could be convinced on using it; my only issues with it skin sensitivity and whether it is safe to use around the eye area; I read that it can cause corneal necrosis. Also, it can end up turning into benzaldehyde which may also sensitise skin and reduce preservation efficacy. 

[LuisJavier]

@MarkBroussard mainly because I can buy phenoxyethanol separately and it is significantly cheaper than my supplier offering it with EHG. I don’t know if I could find EHG separately and I don’t know if EHG+phenoxyethanol gives broad spectrum preservation or if I could replace EHG for something much cheaper. 

[LuisJavier]

@letsalcido tbh I’m not so sure that 3 or 4% glycerin would not impact the feel of a cream; I think it would since it is so sticky when compared to PG. 

[LuisJavier]

Maybe the essential oils are sweating out at the top? If this is the case, I think that the more the EO%, the worse the sweating would be. 

[LuisJavier]

I would recommend you to not use rosewood oil so as to avoid worsening its endangered status. Cetearyl alcohol is not sufficient for emulsification. It can help keep emulsions stable though. 

[LuisJavier]

Benzyl alcohol is far better at dissolving vanillin than benzyl Benzoate. I’ve tested it out myself. 10% vanillin in benzyl Benzoate seems to be the maximum inclusion rate, and around 32-34% vanillin in benzyl alcohol. Both at room temperature in the UK. The only reason I see to use a 50:50 mix of both of these solvents is if you don’t want to use too much benzyl alcohol due to the restrictions in a category 4 application (fine-fragrance spray intended on skin).