Home Cosmetic Science Talk Formulating Impact of Brief pH Drop on Emulsion Stability and Buffering System

  • Impact of Brief pH Drop on Emulsion Stability and Buffering System

    Posted by Anca_Formulator on March 29, 2024 at 12:18 pm

    Hello everyone,

    I recently encountered an issue with a 600g batch of emulsion and would appreciate your insights on the potential impacts on stability and the buffering system.

    Formula Composition:

    • Water Phase: 83% - water, humectants, Vegeluron (Water /Aqua (&) Propanediol (plant based) (&) Tremella Fuciformis (Snow Mushroom) Extract (&) Gluconolactone (&) Calcium gluconate), and 0.2% sodium phytate for buffering
    • <strong style=”background-color: var(-bb-content-background-color); font-family: inherit; font-size: inherit; color: var(-bb-body-text-color);”>Oil Phase: 16.5% - 2% Heliosoft (Glyceryl Behenate, Behenyl Alcohol and Lecithin) + 14.5% (esters, hydrocarbons, 2% brassica alcohol, and small % of plant oil)
    • Preservative: 0.5% Germall (effective pH range 3-8)

    pH Adjustment Challenge: Initially, the emulsion’s pH was 8.4. My target was pH 5.3. After slowly adding 88% lactic acid over 30 minutes and achieving minimal pH reduction, I let the emulsion sit overnight. The next day, the pH rose back to around 6.4. Adding just 2 drops of 44% lactic acid under overhead stirring dramatically dropped the pH to 3.19. I quickly adjusted it back to pH 5 within 2 minutes, but noticed a slight reduction in viscosity. Heliosoft, a key component, is not recommended for use below pH 5.


    1. Could the significant pH drop from the addition of 44% lactic acid indicate an exhaustion or alteration of the buffering capacity of the system?
    2. Given Heliosoft’s pH sensitivity, might this brief excursion below pH 5 have compromised the long-term stability of the emulsion, as evidenced by the immediate viscosity loss?

    I understand that observing the emulsion’s stability and pH over time is a definitive way to answer these questions. However, I’m hoping for preliminary insights or experiences that could shed light on these concerns.

    Thank you for your expertise and advice!

    ketchito replied 2 weeks, 2 days ago 2 Members · 4 Replies
  • 4 Replies
  • Anca_Formulator

    March 29, 2024 at 4:54 pm

    Help please! This is the third batch I made and the pH the next day is 1.5 points higher. The difference in temperature is from 65 F to 63, so not huge. I calibrate the pH meter every time I use it. What is going on here? Like I said there is 0.2% sodium phytate in it.

  • ketchito

    April 1, 2024 at 6:51 am

    If you can, replace your Vegeluron (Gluconic acid and Calcium gluconate are probably buffering your system) for Glycerin. If you can’t, at least reduce Vegeluron amount to the minimum.

    • Anca_Formulator

      April 5, 2024 at 1:03 pm

      Thank you so much. I was wondering if that had something to do with it. Following your hint, I nudged the percentage down a bit. Then, two more culprits popped up:

      • The pH of the water phase was at a startling 10.75! Heliosoft suggests a 0.2% Sodium Phytate concentration over the usual 0.1%.
      • Blending a few drops of the lactic acid adjuster into a 600g emulsion turned out to be quite the challenge (I’m using the overhead stirrer for this). Normally, my batches are in the 250-300g range for R&D in the lab. So, how to effectively mix a few drops into such a hefty amount has been a bit of a head-scratcher. To sidestep this hassle, I adjusted the pH upfront, in the water phase. How do you disperse drops into larger volumes?
  • ketchito

    April 5, 2024 at 8:34 pm

    You can make a solution of your Lactic acid, so it’s easier to measure the amount you need. Or perhaps you meant that because of the high viscosity of your product, it was hard to mix the acid.

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