In this post on white willow bark, Heela asks: I wonder if this needs to be in a product that has a pH between 3-4 like traditional salicylic acid? Also, if it is in a higher pH formulation, does the salicylic acid become neutralized or can you drop the pH and retain the benefits?
No, it doesn't need to be at a pH that low, as far as I know. The liquid versions I have used - like his one from Formulator Sample Shop and this one from Lotioncrafter - have a pH of 4 to 6.5, and this is the recommended pH usage range. This is one of the reasons to use willow bark over salicylic acid: It's easier to formulate with it and you don't need to use a specific solvent, like alcohol, to dissolve it.
In this post on Optiphen ND, Deb asks: So - if the dehydroacetic acid can be deactivated by proteins, does that mean that this is not the best preservative to use with lotions with goat's milk in them or any of the hydrolyzed proteins?
My short answer is yes, I would avoid using those ingredients. My longer answer is yes, but I'm not sure I'd want to use Optiphen ND at all, to be honest.
In the post, I write: Dehydroacetic acid is one of our organic acids. It has great fungicial properties but low bactericidal properties, so it's a good addition to this mix to make it a broad spectrum preservative. Unfortunately, it tends to work very poorly when included at a pH of 5.0, and it can be inactivated easily by cationics, non-ionics, and proteins.
There are two other preservatives in this product - phenoxyethanol at up to 81%, which has good activity against Gram positive and Gram negative bacteria as well as yeast, and benzoic acid up to 12.5%, which is a good fungal fighter - so those will take up the slack, but I'd use it at maximum allowable amounts of 1.2%, which will give you about 0.97 grams phenoxyethanol and 0.15 grams of benzoic acid in every 100 gram batch of lotion.
Can I be honest? I'm a little nervous when I see a preservative that can be inactivated by common non-ionic ingredients, like Polawax or polysorbate 20, and cationic or positively charged ingredients, like BTMS-225 or BTMS-50, because that leaves us with what kind of emulsifiers? Anionic ones, and something like Ritamulse SCG is slightly anionic (although there's a debate about that), so it's really not a suitable preservative for any lotions we might make. You have a really small window of pH for this preservative - you want to be at 5.1 to 6.0 or so - and it seems like it's only suitable for anionic products, like those with foamy and lathery surfactants, so body washes, shampoos, or facial cleansers.
Please note, I have never used this preservative. I'm going by the data sheets and information I've learned about preservatives.
I really can't stress enough how much I need you to include your complete recipe and process to troubleshoot something. Although I've been writing people back lately to ask for that information, if you don't get an answer your question, it might be because you didn't include this in your comment or e-mail. I honestly don't have time to go back and forth to get that information. Please include it in your initial contact with me and it makes answering your question so much easier!
As well, I can't stress enough checking out the FAQ before you write to me. I'm happy to hear from you, but you'll find the answer your question about suppliers in your part of the world in that section, not by writing to me. My response will be to send you there as I don't know where you live and don't know the suppliers near you. The people who live near you are the experts you seek as they have shopped with these suppliers and offer their insider knowledge know about suppliers, and they've commented in those sections. I can't encourage you enough to visit the FAQ!
See you tomorrow!