Home Cosmetic Science Talk Formulating Handwash going ‘gelly’ at nozzle?

  • Handwash going ‘gelly’ at nozzle?

    Posted by Benz3ne on December 7, 2020 at 12:13 pm

    Background
    So, I’ve had some fun tinkering with a basic (read: very basic) hand-wash formulation. Feels good on the hands, foams well, not too harsh, is repeatable and incorporates essential oils well (I’ve tried at over double the quantity listed and it’s still a-okay). Only thing is, as I’ve noticed when dispensing from a cheap hand-pump bottle is that it dries and ‘gels’ around the nozzle. Thereafter, the nozzle has the potential to squirting it unpredictably (not happened yet but I can see it happening…).

    Formulation (w/w%):

    • SLES (28% active): 40%
    • CAPB (30% active): 10%
    • CDEA: 2%
    • Glycerine*: 2%
    • ‘Preservative’**: 1% 
    • Citric acid: 0.3%
    • Polyquaternium-7***: 0.2%
    • Fragrance (typically sweet orange essential oil): 0.15%
    • Dye (sunset yellow, orange tint): 0.05%
    • NaCl (as 10% soln): qs, typically 1.8% as 10% soln.
    • Water (distilled): qs to 100%

    *I know, inhibits foam and kills viscosity, but the viscosity of the resulting mixture is actually quite nice and foams well enough for me/those who have tried it, will explain rationale later.
    ** I have methylparaben and preservative 12 to hand. I’m aware that neither are exactly ideal but have incorporated both without issue just to prove to myself that it can house something typically preservative.
    ***I don’t believe it’s 100% active. 0.3% is a bit too slippery but 0.1% isn’t particularly notable. 0.2% feels nice.

    Glycerine rationale: Glycerine is humectant. Humectant aids water retention. More water retained = less ‘dry’ product around edges of bottle/dispensing nozzle. Less dry product = less gellish stuffs occurring.

    Question
    Could adding more of something humectant reduce the likelihood of the ‘gel’ type stuff I’ve been noticing around the end of the nozzle? It looks suspiciously similar to ‘drier’ SLES, so am assuming that this is the culprit. Would adjusting the % actives towards more CAPB and CDEA in lieu of SLES reduce this effect?

    Benz3ne replied 3 years, 2 months ago 4 Members · 7 Replies
  • 7 Replies
  • ketchito

    Member
    December 7, 2020 at 1:53 pm

    @Benz3ne When you use high levels of CAPB in the presence of (also) high SLES and CDEA, you get faster to a gel phase, especially if you add NaCl. Usually, you want to get closer to it, but with some room to operate. Your could reduce the CAPB and increase CDEA a bit, or reduce CAPB and Increase SLES and NaCl a bit.

  • Benz3ne

    Member
    December 7, 2020 at 3:12 pm

    ketchito said:

    @Benz3ne When you use high levels of CAPB in the presence of (also) high SLES and CDEA, you get faster to a gel phase, especially if you add NaCl. Usually, you want to get closer to it, but with some room to operate. Your could reduce the CAPB and increase CDEA a bit, or reduce CAPB and Increase SLES and NaCl a bit.

    Great, thanks for the response. The funny thing is, it’s more when it’s drying it’s forming the ‘gel’. Gel is probably the right word but doesn’t describe the situation as well as I’d like. It’s more like concentrated formulation, sans water. As if you had left it dry in open air, so a similar consistency to 70% SLES. 
    The mixture in the bottle is still good - it’s free-flowing but viscous and makes a nice ‘blob’ in your hand when dispensing. This remains the same and doesn’t tend any further towards gel after it’s been produced, so I’m happy with the resulting viscosity otherwise. 
    The suggestions you make are definitely interesting - the SLES predominates the surfactant portion of the formulation at around 11%, with the others contributing around 3% and 2% respectively for CAPB and CDEA respectively (not a million miles away from the 6:2:1 ratio that’s touted for basic hand-wash formulations).

    Thanks for the comment, food for thought!

  • bill_toge

    Member
    December 7, 2020 at 8:34 pm
    it’s the product itself drying out - the root cause of the problem is that once the product has been dispensed, there’s a little bit of it left in the pump, and the bit that’s exposed to the air dries out over time, causing the gel effect
    the best thing I can suggest is to try different pump designs
  • Benz3ne

    Member
    December 8, 2020 at 10:18 am

    Bill_Toge said:

    it’s the product itself drying out - the root cause of the problem is that once the product has been dispensed, there’s a little bit of it left in the pump, and the bit that’s exposed to the air dries out over time, causing the gel effect
    the best thing I can suggest is to try different pump designs

    This was my assumption. The curveball for me is seeing similar pump designs where this hasn’t occurred (with some shop-bought formulations). I just had the (albeit dim) lightbulb moment of, if there’s more humectant/hygroscopic components, can it remain more ‘fluid’/less dry until the next dispense? I’ll have to look at what other pump designs are available to me to try out. 
    Thanks Bill, for taking the time to come here and comment.

  • Achieve

    Member
    December 11, 2020 at 2:47 pm

    I think you have great formula, merely add 2% Propylene Glycol and then see the difference…. 

  • Benz3ne

    Member
    December 21, 2020 at 9:41 am

    Achieve said:

    I think you have great formula, merely add 2% Propylene Glycol and then see the difference…. 

    Very kind, thank you. It’s pretty basic but it feels nice on the hands and isn’t too drying in my opinion. It’s been well received by colleagues who have tested it, so I’m fairly happy with it.
    I’ll try with a little PG and see what differences that makes, thank you!

  • Benz3ne

    Member
    January 18, 2021 at 2:58 pm

    Am I missing something here, or overthinking it?
    If you’re to the left of the peak of the salt curve, then wouldn’t drying increase the effective concentration of salt and subsequently cause additional gelling?
    Could being to the right of the peak in the salt curve, so having gone past peak viscosity, mean that during drying the effective salt concentration will rise towards the peak, so not cause additional gelling of the SLES/CAPB mixture? At least, for long enough for it not to gel at the nozzle between uses?

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