Hygroscopic ranking of vegetal and mineral powder

deneuxbendeneuxben Member
edited June 18 in Advanced Questions
Hello everyone !
I am working on a solid shampoo bar that I make via compacting. (mostly SCS @ around 70%, a small water phase and a bit bigger oil phase) I have heard that adding a fine powder of some sort would help the compacting (filling the small holes?). I have issues with the shampoo breaking down the line.... So I would like to add one that is in the list below, since it is available to me.
But, I have been warned by @Imosca that I should not incorporate too much hygroscopic material in my solid shampoo. Hence, I would like to know how hygroscopic are these material ? Is there a way to find this out ? My objective would be then to select the one that is least hygroscopic...
Maybe not only the material counts but also its particule size ?
  • zea mays starch
  • avena sativa kernal flour (50 microns)
  • Distarch phosphate (modified rice starch)
  • arrow root powder
  • hydrolyzed pea protein (90% protein)
  • illite (green or red clay)
  • kaolin (white clay)
  • Rhassoul, maroccan lava clay
Thanks for your help !
Have a great day :)

Comments

  • Nope ? no comment ? maybe I put it in the wrong section .... :neutral:
  • PerryPerry Administrator, Professional Chemist
    You didn't put it in the wrong section. Maybe no one knows the answer. Or perhaps someone who does know the answer didn't see your question. You only posted yesterday. Sometimes it takes time.

    But with many formulation questions you have to experiment to find out the answer. It's unlikely that these ingredients have been compared in the way that you've asked.  Here's an example study but it doesn't look at exactly the materials you asked about. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3909156/


  • deneuxbendeneuxben Member
    edited June 18
    Hi @Perry,
    THank you for your reply. Yes indeed I have to be more patient, I agree.
    I did not really have the expectation to get a nice scientific review that compares them all together according to the same protocol, but since I have put different product "type", clay vs starch for example, I thought maybe some general trend would  be obvious for some of you.
    Like for example: "clays are way more hygroscopic than corn starch"
    From the publication you shared, correct me if i'm wrong, but I understand that the flowability of the powder impacts the compacting process and for me, the more flowable it is, the better.
    At least now if I see studies on the flowability on starch, i could relate to it a bit.
    Thanks.
  • PerryPerry Administrator, Professional Chemist
    "the more flowable it is, the better."  - Sounds like a reasonable conclusion.

    As far as the original question, you'll find that there are a lot of fundamental gaps in our knowledge about all kinds of materials & topics. This is for a few reasons. 

    1. Cosmetic science is a very broad subject (skin care, hair care, color, chemistry, biology, psychology, etc.) so there is a lot that can be studied.  That also makes it difficult to develop a deep expertise in everything. Often experts won't know the answer to what seems like a simple question.

    2. Unless there is some financial incentive to conduct some research, it usually isn't done. And when it is done, companies who paid for the research don't want to publish the results. The cosmetic industry remains a competitive one & not everyone freely shares information. In truth, this forum is an anomaly.

    3. Published research isn't always reliable. This isn't to say that companies are lying, but you shouldn't look at things published about raw materials as settled science. When research is paid for by a company, they are only going to publish positive results. They'll file away any negative results which skews the scientific record. Certainly, there is some settled science with materials that have been around for a long time. But for new materials, it's best to remain skeptical.

    Specifically to your question, the only companies that would pay for this research would be raw material suppliers. And the supplier of zea mays starch may have tested their compound against arrow root powder or hydrolyzed pea protein, but unless there is some marketing advantage they won't be inclined to publish it.

    That's why many basic questions can only be answered with...you have to test it to find out.
  • Thank you @Perry for this big picture feedback ;)
  • Cafe33Cafe33 Member
    avena sativa kernal flour (50 microns)

    Do not waste your time with this! Unfortunately I did. I was designing a rice and oat creamy facial exfoliant syndet bar. I had the marketing story figured out.

    I started testing the material at 1.5%. It made the bar weak and left a sticky feeling on the skin. Even at 0.1%, it compromised the integrity of the bar. I eventually tried using the Avena Sativa Oil instead and just decided to shelve this idea.  

    I was able to come to these conclusions because I had a solid baseline formulation. This is something I believe you are missing. Shampoo Bar/Syndet bars are very sensitive to the slightest change and you do not necessarily have a solid formulation to start with, 

    Also, the faster you realize that most of the ingredients you think are functional in a shampoo are actually just claim ingredients (Fluff), the more you will be able to concentrate on the proper formulation of a syndet bar. 

    As of last September, I had never formulated a single cosmetic product. I do have a background in compressed solid products so I had an advantage when starting out, but it took many tries to come down to a proper base formulation. 
  • PharmaPharma Member, Pharmacist
    deneuxben said:
    ...Hence, I would like to know how hygroscopic are these material ? Is there a way to find this out ? My objective would be then to select the one that is least hygroscopic...
    Maybe not only the material counts but also its particule size ?
    • zea mays starch
    • avena sativa kernal flour (50 microns)
    • Distarch phosphate (modified rice starch)
    • arrow root powder
    • hydrolyzed pea protein (90% protein)
    • illite (green or red clay)
    • kaolin (white clay)
    • Rhassoul, maroccan lava clay
    ...
    From a scientific point of view, these materials are not hygroscopic except for pea protein if highly hydrolysed.
    And yes, there is a way to find out how hygroscopic an ingredient is: measuring RH.
    In your case, all ingredients (especially the clays) will have high batch-to-batch variation and adsorb water to some extent. This 'extent' depends mainly on surface area (in case of starches/flours, this depends on particle size whereas pore size predominates in clays) and correlates directly with RH (or surrounding water if used in a soap bar).
    The effect of water adsorption can go either way -> maybe just ask 'Which one works best in a solid soap bar' ;) .
  • ozgirlozgirl Member, PCF student
    Have you tried adding some of the SCS as a fine powder to help with compacting?
  • Hello all,

    @ozgirl, I will receive soon the SCS in powder form, I will try that :smile: 

    @Pharma Which one worked best in a solid soap bar ? pretty please ? ;)
    I am not equipped with something to measure RH unfortunately. If I understand your point about starch, the finer the grain is, the more susceptible it is to adsorb water (more surface area)

    So far I have stayed away from clays because of their reputation to be hard to preserve. But it seems to me that you are implying this would be the best choice here (less batch to batch variation) ?

    @Cafe33 it is good to hear from your experience. Like you, I am new to formulation. But unlike you, I have zero experience in compressed solid products. Would you be so kind to give me a hint ? please please :)
    I have done many trials. I am happy with the effect on the hair, the cleaning and all, now I am trying to get a good cohesion within the bar. So far it tends to stick to the surface you put it on, and then you loose some product when you pick it up

  • Cafe33Cafe33 Member
    Well, if you have been using strictly the noodle form of SCS, you are already looking at an easy improvement using powdered form. Binding noodles is not effective. You need around 45-55% powdered surfactant.

    My preference is SCI with some SCS noodles blended in.  In fact, many of the DIY recipes are completely off. Your best bet is to shut these out. I like to use 30% Active CAPB. The water content will act as a binder. There are things like colloidal silicon dioxide that increase cohesion but if your ingredient ratios are right, you will not need it.  

    Shampoo bars are Syndet bars and follow the same guidelines already established by the industry. 
     
    Read Chapter 4 of 

    Soap Manufacturing Technology, Second Edition. 

    This is crucial reading if you plan to make the best possible product.

    Also, a final tip for you is to first develop a base formula without any additional ingredients like clays and starches. 

  • PharmaPharma Member, Pharmacist
    deneuxben said:
    ...
    @Pharma Which one worked best in a solid soap bar ? pretty please ? ;)
    I am not equipped with something to measure RH unfortunately. If I understand your point about starch, the finer the grain is, the more susceptible it is to adsorb water (more surface area)

    So far I have stayed away from clays because of their reputation to be hard to preserve. But it seems to me that you are implying this would be the best choice here (less batch to batch variation) ?
    ...
    I don't know, I'm not a soap guy ;) . Else, I'd already told you.
    RH just requires a cheap hygrometer and a jar. But as said, with those ingredients absolutely pointless.
    The finder starch grains are, the more water they will adsorb, correct.
    And yes, clays are hard to preserve and no, I'm not implying that they were the best choice. What I said is that they have a very large surface and will therefore adsorb more moisture than starch. As said, I'm not a soap guy and can't tell you which product works best (or worst). All I'm saying is that these ingredients aren't hygroscopic but they will take up some of the moisture within the soap. However, they are not very likely to have the soap 'suck up' water from the environment like hygroscopic ingredients would.
  • Hello @Cafe33,

    Thanks a lot to giving some hints, I appreciate it.
    Yes indeed, I hope that the powder form will be already a big plus.
    My guess is that I have two main issues:
    1. my compacting process: For now it is very manual and not optimized at all, I think it leaves air pocket which leads to a crumbly texture.
    2. The chemical bonds: I think, if the bar wears off so much is that it does not have enough internal cohesion to resist to the surface attraction/tear (when you leave it on a surface while wet)

    For point No. 2, I will try if adding some emulsifiers help in this ? after all, I have water loving molecules mixed with lipophilic compounds. Emulsifier does not sound so bad to me to hold them together, no ?

    For point No.1: I am a bit confused. I agree with you to do simple formula to develop a good base, but in this case I though that the purpose of the clay or starch was to enhance the compacting step (I guess the fine powder fills the small wholes). So I understand that you say it is not a must to develop a good base already, isn't it?

    For liquid surfactant (like CAPB), I am using coco glucoside, in small amount, like 4%. I was thinking to take that off. I added it to make a milder synergy with SCS, but I wonder if it does not make the product more sticky in a way, or help in any way at all... DO you think this is crucial ? I mean, if this is for the water content, I can add the water alone.

    I am going to go read that book, chapter 4 ;)
  • @Pharma thanks a lot for the clarification ;)
  • Cafe33Cafe33 Member
    deneuxben said:

    1. my compacting process: For now it is very manual and not optimized at all, I think it leaves air pocket which leads to a crumbly texture.

    This is an issue with improper binding. Using fine powdered surfactant with a wetting agent - water in CAPB for example will resolve "air pockets and crumbly texture". Binder is usually used at 4-6%. Use too little and it crumbles. Use too much and it stays wet and soft.

    2. The chemical bonds: I think, if the bar wears off so much is that it does not have enough internal cohesion to resist to the surface attraction/tear (when you leave it on a surface while wet)

    Look at Sodium Lactate/Sodium Chloride and what they can do in Syndet Bars. 

    For point No. 2, I will try if adding some emulsifiers help in this ? after all, I have water loving molecules mixed with lipophilic compounds. Emulsifier does not sound so bad to me to hold them together, no ?

    Yes, adding an emulsifier is a great idea. I have used BTMS, Polawax, Lanette N, Glyceryl Stearate with great success in these types of bars. BTMS is best for a light conditioning shampoo. 

    For point No.1: I am a bit confused. I agree with you to do simple formula to develop a good base, but in this case I though that the purpose of the clay or starch was to enhance the compacting step (I guess the fine powder fills the small wholes). So I understand that you say it is not a must to develop a good base already, isn't it?

    Different powders compact differently. I certainly don't believe that these types of starches and clays will help you create a compact mixture. 

    For liquid surfactant (like CAPB), I am using coco glucoside, in small amount, like 4%. I was thinking to take that off. I added it to make a milder synergy with SCS, but I wonder if it does not make the product more sticky in a way, or help in any way at all... DO you think this is crucial ? I mean, if this is for the water content, I can add the water alone.

    Glucosides weaken the structure of the bar. I don't know why, but that has been my experience (even at 2%) The bar will snap in half even after a few uses.

    I am going to go read that book, chapter 4 ;)


  • This is an issue with improper binding. Using fine powdered surfactant with a wetting agent - water in CAPB for example will resolve "air pockets and crumbly texture". Binder is usually used at 4-6%. Use too little and it crumbles. Use too much and it stays wet and soft.
    I have no experience with wetting agent, but trying to make sense of your comment: What I understand is that it could help to add a wetting agent (emulsifier with HLB value around 7-9). If I guess well, that would help the binder (water at 4-6%) "adhere" to the solid surfactant by reducing its surface tension correct?

    I have for example at my disposal sodium stearoyl lactylate which is a water soluble emulsifier with HLB 8.3

    I have also Olivem 1000 (Cetearyl olivate, Sorbitan olivate) HLB 8-9 and Xyliance (Cetearyl wheat straw glycosides, cetearyl alcohol) HLB 8
    But these two are oil soluble, it would not be a good choice no ?

    Look at Sodium Lactate/Sodium Chloride and what they can do in Syndet Bars.
    I have added sodium lactate (ca 60%) @1%, I could not say I saw improvement. But I will look into the science of this, thanks

    Yes, adding an emulsifier is a great idea. I have used BTMS, Polawax, Lanette N, Glyceryl Stearate with great success in these types of bars. BTMS is best for a light conditioning shampoo.
    I am glad to see that cationic emulsifier (BTMS) works and does not disturb the structure (I was not sure the positive charge would do well in presence of the main anionic surfactant). I wish to add Brassica Alcohol (and) Brassicyl Valinate Esylate for its conditioning properties.


    Different powders compact differently. I certainly don't believe that these types of starches and clays will help you create a compact mixture.
    I see, I'll stop playing with them for now, plus they may not be that much necessary once I get the powdered surfactant.

    Glucosides weaken the structure of the bar. I don't know why, but that has been my experience (even at 2%) The bar will snap in half even after a few uses.
    Well, I was already convinced about removing it, I will do so. Thanks for the feedback !

    Have you tried with sodium cocoyl glutamate, either as main surfactant in powder form, or as your secondary in dilution, does it work well ?

    Thank you very much overall for our exchange, it gives me new perspectives for development, I was a bit reaching a dead end without new ideas and information, now I have a lot of work ahead :)


  • Cafe33Cafe33 Member
    Wetting agent is a term used in wet granulation. I used it interchangeability with binding agent but it is not correct. I am used to water/alcohol only as a wetting agent which is then dried and not so much a binder. Anyway, all this to say, it doesn't matter :smile:  

    Aim for the following ~70% Surfactant mix (I use SCI/SCS/CAPB) and 4-6% total water. 

    I started out using SLSa but found that SCS cleans in a superior way (big surprise) I only use SLSa for facial washes now.

    As far as emulsifiers, pick between BTMS or Polawax. 

    Again, you will be much better informed after you read the chapter I told you about. 
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