[BathroomChemist]

So I called PURE Bioscience to ask about Silverion 2400, and while it is listed as being compatible with Polysorbate 80, the R&D lead said that only applies to a low percentage. My concentration is way too high. I think I’ll order the DMDM, but I may also explore another surfactant like Kollophor EL (PEG-35 castor oil) to replace the Polysorbate 80. Anyone have experience using these, or know preservative compatibility?

[BathroomChemist]

Thanks all, I just added a 2 oz bottle of DMDM to my cart on Making Cosmetics. It sounds like many of you are fans of DMDM based on other posts about preservatives.

Another interesting one I found last night was <font color=”rgba(0, 0, 0, 0)” face=”inherit”>Silverion 2400 by PURE Bioscience. I’m normally </font>skeptical of silver-containing products, but it’d be unfair to write silver off. I used to work in a field where researchers were impregnating porous clays with silver nanoparticles to purify water in the developing world. Anyone have experience with this product? pH would need to be below 7, but it’s supposedly compatible with non-ionics. I’ll try calling the company today and report back.

[BathroomChemist]

Quick update. I found the article “Compatibility and efficiency of preservatives in emulsive cosmetics containing high surfactant content”, which cited a paper claiming phenoxyethanol incompatibility with non-ionic surfactants. It also paints a grim picture for preserving micro and nanoemulsions with parabens, phenoxyethanol, and benzoic acid. Very interesting and worth a read. I’ll have to do more research on alternatives this weekend. I welcome any suggestions in the meantime.

[BathroomChemist]

I know you addressed this to Phil, but I may be able to provide a bit of guidance here. Many sources that talk about the incompatibility of phenoxyethanol with non-ionic surfactants can be traced to a single reference, which is “Sheskey PJ, Cook WG, Cable CG. Handbook of Pharmaceutical Excipients”. I got free access to the 6th edition. On Page 489, it says, “The antimicrobial activity of phenoxyethanol may be reduced by interaction with nonionic surfactants…[14]”. The citation for this is “Lee MG. Phenoxyethanol absorption by polyvinylchloride. J Clin Hosp Pharm 1984; 9: 353–355″.

[BathroomChemist]

Hi Ketchito, I have access to cryo-EM and a Zetasizer so I can characterize size and surface charge. I’m doing some tricky things with the oil phase, and that got me a microemulsion range over 67% of my ternary plot (10-80% of each ingredient, increments of 10%). If I dilute the samples (1:2 ME:Water) this area drops to 50% (adding a tiny of PEG400 to hazy vials increased this to 59%). The microemulsions are transparent and very fast absorbing. A few samples are the slightest bit hazy, and a few are translucent with a brilliant opalescence. I haven’t measured the size of these, but they’re probably something like 100-200 nm. I’ve stabilized those sample with a tiny bit of PEG400.

What small alcohols do you recommend? I tried n-butanol for the fun of it because I happened to have some in my bathroom, and it cleared some of the cloudy (diluted) samples, but that’s obviously not suitable for cosmetics!