Home Cosmetic Science Talk Formulating Salts (magnesium and citrates) causing transparency loss in cleansing formulation

  • Salts (magnesium and citrates) causing transparency loss in cleansing formulation

    Posted by Anonymous on March 12, 2016 at 7:02 am

    Some insight from all you mighty formulators.
    I’m trying to make a transparent handwash liquid with mainly SLES and LAS. After all the ingredients are added, my solution is translucent but runny. I gather from the discussions here and the books I have read that I should try to experiment with magnesium and citrate salts to thicken the formulation in the end (causing the spherical small micelles to transition into worm like bigger micelles -> viscosity increases). The problem is that as soon as I mix these salts, my sample looses all its transparency and is completely white. I have also tried Sodium salts and citric acid instead… nothing helped.

    So I’d like to find out
    1. if there are other options to adding these salts?
    2. if these salts have any other function in the formulation (such as preservative or foam enhancer or something)?
    3. If not, can polymer additives work for viscosity increment problem?
    4. If yes, what (and how, if possible)?
    5. For chemists who are in similar <transparent liquid> boats, what do you do to resolve the transparency issues?
    Thanks so much.

    belassi replied 8 years, 3 months ago 5 Members · 10 Replies
  • 10 Replies
  • belassi

    March 12, 2016 at 3:19 pm

    List the formula and you might get a meaningful response.

  • Anonymous

    March 14, 2016 at 4:31 am

    Okay… Here are the materials:
    Purified Water as Base
    SLES 9%
    LAS 2%
    Lauric acid 3%
    Till here, my mixture is a translucent mixture.
    Now I am told to add 2% MgSO4 and 1% Sodium citrate to it. At this point, it becomes completely turbid (pH 7). When I adjust the pH to my required range of 4-5, this transitions from a white goop kind consistency to white runny liquid. I need this formulation to be clear in visibility and somewhat thick in consistency. The maddening thing is my employers won’t tell me what purpose the additives are to serve… That way at least I can play around with the ingredients/ compositions a little.

  • belassi

    March 14, 2016 at 5:40 pm

    This is a bit outside my usual areas but I’ll try to help.

    First, you are combining low active levels of anionic surfactants, a polar solution, with a nonpolar substance, the lauric acid. What’s the idea of that? Refattening? There would be better ways to achieve that. I am surprised that the relatively low level of actives is enough to emulsify the lauric acid, but apparently so. The fact that you get thickening at all, is due to making an emulsion.
    Second: When you add the salts it becomes runny. Hardly surprising is it? You’re adding 3% salts and expect to stay inside the salt curve?
    Third: If your management withholds vital information from you, I suggest looking for a better job. Seriously.
  • OldPerry

    March 14, 2016 at 7:40 pm
  • Bill_Toge

    March 14, 2016 at 8:06 pm

    @Belassi the management probably don’t know themselves; if a formula is old or poorly documented, it’s not unknown for the rationale behind it to be lost to time once the original creator has left the business

  • Bobzchemist

    March 14, 2016 at 10:09 pm

    I’m wondering if that formula skipped the part about neutralizing the Lauric Acid with Sodium Hydroxide? That’s the only way I can think of that makes sense. 

    Otherwise, you will never get a clear aqueous solution with Lauric Acid at 3%, even if you bump the surfactant level way up.
  • Bobzchemist

    March 14, 2016 at 10:11 pm

    Potassium Hydroxide might be a better choice, come to think of it.

  • ozgirl

    March 15, 2016 at 12:21 am

    When you refer to LAS are you referring to linear alkylbenzene sulphonate? If yes are you using the acid form and then neutralizing it and your lauric acid with sodium hydroxide or other alkali?

    What is the surfactant level in your SLES?

    Have you considered using cocamidopropyl betaine? It will improve mildness and help with viscosity and foaming.

    What are you using to adjust your pH to 4-5? Why do you need the pH to be this low?

  • belassi

    March 15, 2016 at 2:14 am

    Oh, right, Bill. That hadn’t occurred to me. I think Bob is closest to the solution to this. maybe it is a potassium cocoate/SLES/LAS surfactant combination. 

    Try this:
    Calculate (using the SAP value) the required amount per kilo to saponify the lauric acid with KOH.
    Then saponify the lauric acid first, dilute with water, add the SLES and LAS. Mix well. Adjust the pH.
    Then titrate, slowly, with the pre-prepared mix of salts, stirring continuously, until you get optimum thickening. At the same time you do this, record the pH.
  • belassi

    March 15, 2016 at 2:21 am

    Further to my last:

    potassium cocoate 40% soln. is readily available in most places, try adding say 3% of that to your two surfactants, then titrating with the salt solution.
    I also agree with Ozgirl’s suggestion for adding some CAPB, in fact CAPB could be used directly as a thickener with much better results. It contains NaCl.

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