[Bill_Toge]

I should think it’s very unlikely; I’ve certainly never heard of that occurring

[Bill_Toge]

sodium chloride increases the surface tension of the water phase, and reduces its tendency to aggregate, which stabilises W/O emulsions; it’s not necessary in O/W, and if anything is more likely to destabilise it

magnesium salts do the job better still, as they’ve got a +2 charge on them rather than +1

[Bill_Toge]

the yellow colour of CAPB comes from residual impurities, specifically amines - if you’ve got the specifications for each material, compare them side by side

as for decyl glucoside, short-chain alcohols (shorter than C12; decyl is C10) and fatty acids tend to have a naturally strong smell, as do their esters

[Bill_Toge]

your best bet is to remove or reduce the Siligel

[Bill_Toge]

salicylic acid works well

[Bill_Toge]

the fact it’s not permitted won’t stop an unscrupulous brander from using it anyway

[Bill_Toge]

the best client is one who knows exactly (or has a good idea of) what they want, doesn’t change the brief substantially, and is actually committed to buying the finished product

the grief comes when you make sample after sample for them, only to have them rejected because they don’t really know what they want; or they approve a sample for production then change their mind further down the line and make you start again

[Bill_Toge]

given that castile soap is alkaline, I’d suspect it’s due to a dye that’s coloured in alkaline conditions and colourless in neutral to acidic conditions; as the soap is lathered more and more, it becomes increasingly diluted and neutralised, therefore losing its colour

the most likely candidate for the pink variant is phenolphthalein, and the most likely candidate for the blue variant is thymolphthalein

not sure about the green though, it may well be a mixture of 3-nitrophenol (yellow/red) and thymolphthalein (blue)

the one that goes from white to blue is almost certainly due to an encapsulated pigment; Daito Kasei, among others, specialise in this kind of technology

[Bill_Toge]

@ngarayeva001 in my experience, the cosmetic grade stuff is aloin-free, and every batch is tested for it; this may vary from manufacturer to manufacturer

[Bill_Toge]

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

[Bill_Toge]

look up “Aerosil powder-to-cream”, to find out the basic principle of how the product works; you’ll need a lot more water, and a high-shear mixer, to make it work

on small scales, a coffee grinder will suffice, but on larger scales you’ll need something like an industrial blender

also, from experience, hydrophobic polymers like Amphomer work better than VP/VA copolymer, as the latter draws water from the air and causes the product to turn into mush

[Bill_Toge]

@adonason the long and short of it is that thermodynamics favour O/W emulsions, because water has a much stronger tendency to aggregate (due to hydrogen bonding between water molecules) than oil does; W/O emulsions can only be formed when this is minimised

[Bill_Toge]

a good way to make a water-thin emulsion is to use 0.1% low-acyl gellan gum in the water phase, cross-linked with 0.1% calcium chloride (or an equivalent weight of another calcium salt)

if you want a thicker product, add cetyl/stearyl/cetearyl alcohol and/or stearic acid to the oil phase; fatty alcohols will increase zero-shear viscosity (makes it feel thicker), and stearic acid increases the high-shear viscosity (makes it feel richer)

[Bill_Toge]

ketchito said:

@adonason Mixing both O/W and W/O emulsifiers would make the emulsion more stable, which usually translates in more viscosity, which is the contrary to what you want to achieve.

that only applies to O/W emulsions; it’s not possible for W/O emulsions to form with O/W emulsifiers present

[Bill_Toge]

the fundamental problem is that you’ve got nothing in the water phase to physically prevent the oil phase from coalescing and separating; what you need is something that will make the product effectively non-fluid at rest (so the emulsion droplets can’t physically move)

there are several possible ways this can be done - how viscous do you want your finished product to be?

[Bill_Toge]

in a previous job I’d use DMDM hydantoin or isothiazolinones for rinse-off products, or Euxyl PE9010 for leave-on products, plus DMDM hydantoin if there were a lot of suspended solids in the product, e.g. clays

as it stands, I am restricted to Dermosoft 1388 and GMCY, keeping the pH below 6 if there are suspended solids in the product; propanediol at 10-20% helps as well

in fairness, it works well; thanks to a robust preservative system, and a reliable supply of clean sterilised mains water, it’s very rare for us to have a micro count on any of our products

[Bill_Toge]

sciencewannabe said:

Bill_Toge said:

they’re not W/O emulsions; polysorbate 60 and ceteareth-20 are both high HLB emulsifiers, so it’s not physically possible for them to form W/O emulsions

instead of glyceryl stearate, try a low HLB emulsifier that comes in the form of a liquid (polyglyceryl-3 oleate, for instance), and just to be sure, try adding a little bit of xanthan gum (say, 0.1%) to the water phase, to reduce separation

This will take me some time to wrap my head around but I appreciate the reply and suggestions! 

Just to clarify, would I use the polyglyceryl-3 oleate WITH E-Wax calculate HLB, etc. or just polyglyceryl-3 oleate and xantham gum in place of the current emulsifying system? Thanks again! 

yes, you’d need to use PG-3O or similar as well as an emulsifying wax/other high HLB emulsifier; on its own, it won’t form an emulsion at all

[Bill_Toge]

azelaic acid is notorious for being poorly soluble in water and oil alike; what you’re most likely seeing is suspended particles of the acid absorbing any available water or oil

a highly polar oil like butyloctyl salicylate, and an alcohol-like solvent in the water phase e.g. propylene glycol, will help solubilise it

[Bill_Toge]

they’re not W/O emulsions; polysorbate 60 and ceteareth-20 are both high HLB emulsifiers, so it’s not physically possible for them to form W/O emulsions

it sounds to me that your stable formulas are held together by sheer viscosity, and the higher water content of the unstable ones is thinning them and leading to separation on a much shorter timescale; instead of glyceryl stearate, try a low HLB emulsifier that comes in the form of a liquid (polyglyceryl-3 oleate, for instance), and just to be sure, try adding a little bit of xanthan gum (say, 0.1%) to the water phase, to reduce separation

[Bill_Toge]

they could try filling it more slowly, and/or using filling nozzles that go to the bottom of the bottle and fill it up while raising (I’ve forgotten the proper name for this type of filler, sorry)

[Bill_Toge]

hydrogenated castor oil gels the oil phase and makes it non-fluid at rest, which helps stabilise W/O emulsions

magnesium sulphate increases the surface tension of the water phase, reducing the tendency of individual droplets to aggregate, also increasing the emulsion stability

forming a W/O emulsion is working uphill against the laws of thermodynamics - you have to take as many advantageous measures as you can

[Bill_Toge]

it’s very likely incomplete; if it looks and behaves like a typical conditioner, there’ll be a fatty alcohol of some kind giving it a cream-like consistency, and a quaternary ammonium salt acting as the conditioning agent (possibly as the emulsifier too)

[Bill_Toge]

dimethyl isosorbide is an excellent solvent for salicylic acid, and as a bonus, it’s miscible with water

[Bill_Toge]

there are ways to formulate 3-phase emulsions (o/w/o or w/o/w) but it’s a highly specialist technique, and not generally necessary for cosmetics and toiletries

[Bill_Toge]

linear 1,2-glycols are antimicrobial - the efficacy increases as the chain length increases, so caprylyl glycol (C8) works better than 1,2-hexanediol (C6; ‘hexylene glycol’ is a branched 3,5-diol), which works better than butylene glycol (C4)

unless they’re included at 30% +, they’ll not have a significant effect on the water activity