Home Cosmetic Science Talk Formulating Preservative suggestions needed for preservatives in soap formulas…

  • Preservative suggestions needed for preservatives in soap formulas…

    Posted by MarkEMark2 on August 15, 2016 at 8:57 pm

    Hi All:

    Thanks to this forum, I have had some remarkable success this weekend with some cream soap formulations. I have identified a formula mix and am now going to begin beta testing with a few people, and the question of preservatives has popped up. 

    A similar formula uses Methylisothiazolinone and Phenoxyethanol as preservatives.  I am looking for suggestions from you for preservatives that would be good for a shave cream blend of Palmitic acid, Stearic acid with glycerin. 

    1. Which do you recommend (one or both of the above?)

    2. Alternatives that might be acceptable

    3. What will happen to the soap without them (I suppose rotting, but how long typically will it be before this happens?)

    4. What kinds of percent/quantity would be necessary to safely insure the soap preservation from spoiling; ie: what % would I need to add after the batch is finished to insure a quality product. (2 types are listed in my target formula, and I assume both serve a specific function for the product, but I am looking for variations that might work and satisfy the need).

    Many thanks for the help!

    belassi replied 7 years, 8 months ago 3 Members · 7 Replies
  • 7 Replies
  • belassi

    August 15, 2016 at 9:57 pm

    What is the pH?

  • Microformulation

    August 15, 2016 at 10:15 pm

    1. Not enough information to answer. As Bellassi has pointed out, there are multiple factors to take into account.
    2.  Ibid or same as Number 1.
    3. Rot really isn’t the correct term. An improperly preserved product will be susceptible to growth off bacteria, yeast and mold. In the case as here where there could be a high oil content, there could be the need for an anti-oxidant. An improperly preserved product could change color, odor, exhibit instability or even worse be harmful to the client. Again in this case not knowing all the factors makes it difficult to fully predict.
    4. Each product has different usage levels and even the same product has different usage levels for different applications. There is no blanket answer but the distributors provide extensive documentation specific to the product.

    Lastly (and not numbered since not truly a posed question) you should look at Marketing forces as a factor in selecting your preservative. My best example would be parabens. Honestly avoiding parabens has a poor scientific basis but is rather a reaction to a flawed study. Albeit was flawed, it led to a bias against these ingredients.I submit that this market shift has made Cosmetics less safe rather than more safe as we now have to avoid an effective class of preservative. With this in mind, look at some of the issues with Methylisothiazolinone (MIT for short). They are not as simple as the consumer would believe, but it is a rising issue nonetheless. Don’t make market forces the SOLE factor in selecting an ingredient. Keep in mind that performance and cost are equally important as well.

  • belassi

    August 16, 2016 at 12:30 am

    I backtracked along your previous thread and read the patent that Bob kindly referenced. Pretty poor patent really because among other things it failed to refer to the K/Na ratio. Anyway, what I noticed was the “free stearic acid to ensure that alkalinity is not excessive” or words to that effect.
    Which leads me to suspect the pH may be around 9 perhaps and if so a preservative will be required. You will need to pick one that is effective at that pH and also as Microformulation pointed out, one that is consumer marketing friendly. 

  • MarkEMark2

    August 16, 2016 at 12:33 am

    Uh, Slap forehead and shrug my shoulders.

    Ph values. This is the reason I started to post the question over the weekend, and realized I could not answer the Ph question, as I need to find the right strips/measuring process.  I completely forgot this when I posted the question today. Thanks for the gentle reminder.  I will need to order something to test this, and not sure what would be best.

    Any suggestions for a reasonable method to test the Ph of these batches? Would strips be OK for this or do I need a better solution.

    I admit, this one is a really basic question, but I will follow up on your recommendations.

    Thanks again.

  • MarkEMark2

    August 16, 2016 at 12:41 am

    Belassi: I am using the 5:1 K/Na ratio: 5 parts KOH to 1 part NaOH and it appears with a 2 hour cook I get a fairly good saponification, but of course the Ph will tell me how well.  Looks can be deceiving. 

    I added no additional “superfattening” to the mix. I found the initial product satisfactory, but I am not done experimenting.  I am not sure with this mixture what the benefit or added value to the blend would be with a superfat mix (again, experience will tell).

  • Microformulation

    August 16, 2016 at 4:49 am

    As far as pH goes, purchase a meter. The strips are simply not feasible. A meter that can be calibrated can be obtained through several sources.

  • belassi

    August 16, 2016 at 2:49 pm

    ^^^ This. Soap is notoriously difficult to measure.

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