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What makes these two serums different?

Dear Brains,

After recently adding a vitamin C serum into my routine (Paula's Choice C15 booster), I am hoping that I have found a more reasonably priced alternative (NuFountain C20+Ferulic) to continue using long-term ($48 for 0.67 oz vs $21.99 for 1 oz). I like using the PC booster exactly as indicated: adding it into my current lotions to "boost" their performance. This is super convenient because it doesn't alter my existing routine, AND I can mix it into my body lotion and get this serum's benefits all over without going bankrupt. However... while this is awesome in theory, I am super confused about how the PC booster actually works when mixed with other products. Since ascorbic acid requires a Ph below 3.5 to remain stable, how can the PC booster possibly maintain this when mixed with any variety of unknown products? I emailed PC customer service to specifically ask this question and the answer they gave me was very unsatisfying. They said the serum was formulated with this in mind and it has penetration enhancers to ensure that the ascorbic acid is viable when mixing. Here is the full ingredient list:
Water, Ascorbic Acid (vitamin C/antioxidant), Ethoxydiglycol (slip agent/penetration enhancer), PPG-26 Buteth-26 (emulsifier), PEG-40 Hydrogenated Castor Oil (thickener), Tocopherol (vitamin E/antioxidant), Ferulic Acid (antioxidant), Sodium Hyaluronate (skin-repairing ingredient), Acetyl Octapeptide-3 (cell-communicating ingredient), Glycerin (skin-repairing ingredient), Panthenol (skin conditioning agent), Sodium Metabisulfite (stabilizer/antioxidant), Triethanolamine (pH adjuster), Phenoxyethanol (preservative)

Now, as for NuFountain, I emailed their customer service and asked about mixing their product into a cream immediately before applying and got a very different answer. Their logic is on the same line as mine with the PC booster: It needs a special Ph to be stable, so mixing it will likely affect the Ph and render the ascorbic acid useless. They not only said that their serum should not be mixed with others before applying, but also that their serum should be applied first to allow full absorption of the ascorbic acid without any chance of altering its efficacy. Here is the full ingredient list of that serum:
Purified Water, 20% L-Ascorbic Acid, Ethoxydiglycol, DL- Panthenol, Glycerin, Magnesium Sulfate, Ferulic Acid, Sodium Hyaluronate, Sodium PCA, Phenoxyethanol, Caprylyl Glycol, Sorbic Acid

There are a couple of additional ingredients at the end of the PC booster ingredient list, but the only penetration enhancer (the star player of the booster serum according to the PC email) is present in both serums. So what is going on? Are these two serums really redically different in terms of stability, or is someone just wrong here?


  • Not to hijack, but a two-for-one question...

    Could you also advise whether these serums must be kept in the refrigerator? Thanks.
  • First the easy one. Well, sort of easy. For a lot of products, it doesn't hurt to keep them in the refrigerator because the lower temperature slows down reactions and extends shelf life. (Just don't freeze them.) However, according to Paula's website, this product should NOT be stored in the fridge. 

    Now for the tougher one: If I understand your basic question, you want to know if these products can be mixed with other products to make an easy to use "2 in1."  You're right that ascorbic acid has to be in a certain pH range to work properly. I don't see how a small amount of this booster could lower the pH of a large amount of a secondary product. Perhaps all of Paula's products are formulated in the proper pH range? That could explain how Paula gives you one answer and NuFountain gives you a different answer. I really don't know. 

    If I had to pick one product I'd guess the Paula's Choice is more stable given the use of tocopherol and sodium metabisulfite. 

  • Thank you, Randy. Paula insists that her booster can be mixed with any product, not just her own, which makes this "stable when mixed" claim seem even more bizarre in my opinion. I think I am leaning towards NuFountain's advice since logically it just makes more sense. Maybe a dark colored, glass spray bottle could make for easier body application with minimal waste? The spray would expose the serum to a lot more air, but only for a split second before it is applied...
  • You're welcome Sam. If you have time to return the favor, it would really help us out if you would write a review of our podcast on iTunes. (Just search for "The Beauty Brains.") Thanks!  
  • Sam, when you use a spray bottle, it has to put some oxygen back in the bottle to equalize the pressure.  For Vitamin C serums I re-use one of those "airless" pump dispensers that came with my anti-aging creams.  The bottom lifts up at each "pump" so that no air enters the container.

    I managed to make 1 oz of serum last 5 months this way.  It ran out before it turned brown - but any that dribbled outside the container turned brown quickly!

    Just be aware that these "pumps" are designed for more viscous creamy material - and the serum will come shooting out.  To prevent wasting it, practice spraying water out of it while you're cleaning the container.


  • Thanks L! The spray bottle didn't exactly work that well... It ended up being more like a jet stream and occasional misses were a thing. I've been using the NuFountain C20+Ferulic serum straight out of the dropper and it's working quite well since that serum has a much more silky consistency than the PC C15 Booster. It spreads easily enough for me to use a few drops over a large area. I do have a glass pump bottle that I will definitely be using for my C serum as soon as it is empty! 
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