[jeremien]

@Doreen … as i read “gelled waterhpase”, i thought that he have already neutralized it before emulsification… it may be a wrong interpretation

[jeremien]

You may neutralize the
carbomer after emulsification… if you neutralize it before, you may have air
bubble entrapment due to high viscosity

[jeremien]

I guess that you can dilute up to 10 times in water and pH should be the same as in your product without dilution

[jeremien]

Does Permulen TR-2 accept small amount of electrolyte?
 

[jeremien]

@ngarayeva001 i trust you J, i have never formulate a product with only
this surfactant. I believe that thickening effect is due to liquid crystalline
phase and stronger interactions with other co surfactant such as cetostearyl
alcohol.

[jeremien]

ultracentrifugation, temperature cycles..

[jeremien]

Looking to phase diagram of both surfactants, due to its slightly differetn structure, Tween 60 tend to form liquid crystalline phases in a larger region than tween 80, maybe that is the reason why you classify it as a thickner?

[jeremien]

I cannot understand why you classify tween 60
as Thickener and not Tween 80. The only difference between both surfactants is
the alkyl tail, that have the same length (C18) but it is a stearyl in the case
of Tween 60 and Oleyl in the case of Tween 80. I understand that tween 60 is semisolid at room temperature and tween 80 is liquid, but when you solubilize them, both are soluble in water. 

[jeremien]

the 3 are surfactants. The structure and the HLB is
different. 

Polysorbate 60 and 80 are very similar and have almost the
same HLB, only difference is the saturation of the aliphatic tail. If you are
using a saturated oil better to use the polysorbate 60 and for unsaturated oil
better the polysorbate 80.  

Polysorbate 20 is more hydrophilic 

[jeremien]

A correction to my previous post:

“The lipid layer in the stratum corneum contains a
high ratio of negatively charged lipids and it is well known that the skin may
act as a negatively charged membrane” (C. Sinico,  et al.J. Control. Release, 103 (2005), pp.
123-136)

[jeremien]

@Gunther, i guess that skin have a neutral
charge, more than attraction I would say compatibility, and as the surface of
the skin is mainly lipophilic I would use lipophilic ingredients if you want
them to have a chance to remain on the skin after cleaning and washing. The balms
option looks interesting.  For
hydrophilic ingredient, encapsulation in a amphiphilic system can be a good
option to remain on the skin.

[jeremien]

i will add that if the cleaner is well formulated you
can solubilized the sebum in a microemulsion instead to emulsify it, and it is much
more efficient.

[jeremien]

For viscosity tuning, recently the raw material manufacturers are coming back with liquid crystalline phase and highly concentrated emulsion
concepts to innovate from the carbomer strategy. 

I guess that for simple viscosity modification, carbomer is very easy, but if you look for adding other properties to your
formulation (skin penetration, stability, feeling, etc.), it may be interesting
to explore these options (LC phase, HIPE)

[jeremien]

@ngarayeva001  depend of the oil content… at a certain point viscosity increase quite a lot (i guess from 40% oil, but that will depend also of the droplet size) and if you superate 74% internal phase ratio, you will have no flow anymore

[jeremien]

Be aware that : 
-pKa of both acids are different. 
-Citric acid is also a weak chelating agent. 
-Lactic acid has some safety concerns (see the CIR report), in particular related with sun exposition
 

[jeremien]

ethanol is smaller and should migrate to the interface (air/water) quicker and destabilize it better

[jeremien]

it is not a simple ingredient, but a mixture:

https://www.cosmeticsandtoiletries.com/research/methodsprocesses/Sticking-it-to-Hair-Damage-Delivery-Duo-Protects-and-Repairs-Inside-and-Out-494523421.html

[jeremien]

Unless you succeed to formulate a nano-emulsion or
microemulsion with these components

[jeremien]

@Perry  after a quick shearch i find this two papers. the second one reports the results from a clinical investigation with Epiceram

https://www.sciencedirect.com/science/article/pii/S0022202X15425643

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3070468/

You are right that they never compare with petrolatum.

In my opinion petrolatum (or lanolin) is purely occlusive. The
main target of petrolatum is to reduce TEWL and, consequently, increase
stratum corneum hydration. Two inconveniences of this mechanism can be the
excessive reduction of skin-breathing capability, or the quick return to a
water loss condition once the occlusive mixture is removed. Indeed, an excessive increase in stratum corneum hydration
afforded by the application of occlusive substances does not lead to the
well-being and protection of the skin. On the contrary, intense dermatitis can
occur simply due to prolonged water exposure.

I guess that regeneration  of the lipidic composition/structure of the SC strategies, can help to long-lasting hydration of the skin.  

In the last decade’s science help us to understand better the composition/structure of the skin, and in particular the importance of the lipidic structure of the SC, and a bio-mimetic approach should be effective. 

Saying that, ceramides are complex molecules complicated (and very expensive) to synthesized, and there still a lot of ceramides molecules to be discovered. Fow now, i only know Evonik product with an affordable price to be used in cosmetic, quite limited choice, and not sure that are the ones present in the human skin. 

[jeremien]

the importance of  the 50% ceramide, 25% cholesterol, 15% free fatty acids ratio in the skin was
studied a lot by Peter Elias. He publishes many papers dealing with the lipid
structure of the skin, and the possibility to regenere SC barrier function
using topical product with this composition. He also actively participates to
the development of the Epiceram medical device based on this composition that
seems to have good results for AD management.  

[jeremien]

Bill_toge is right, at around 30% in water SLES form an hexagonal liquid crystalline phase that is very viscous. The concentration limits of the phases may vary a lot depending the impurities contained in the different batches of SLES.  I guess that the hexagonal phase is present in a large range of temperature (is is the case for SDS not sure with SLES).

[jeremien]

cosmetic industry is using a lot the terminology “sensitive skin”, but i guess that “reactive skin” would be more correct.

[jeremien]

@ great! thank you very much!

[jeremien]

sodium phytate is available from Evonik
I can find sodium levulinate in Alibaba, but for now, alibaba is a no go as it is complicate to control the suppliers

[jeremien]

Penetration through the stratum corneum is not an easy
task. 

- Most enhancer of penetration (e.g. solvent, surfactants, alcohols etc) will damage
the lipid matrix of the SC leading to a loss of hydration of skin,
irritation and further skin and can cause long-term skin disorders.

- Vesicles that are described to penetrate the SC are made with
some surfactants and can lead to the same problems as described before.

- Other lipid vesicles such as liposomes will not
penetrate the SC due to their size. 

- Use of mixture cholesterol/ceramide/fatty acids could be a
good approach as it mimics the composition of the lipid matrix of the SC, but
you have to be sure that these ingredients penetrate the SC

An elegant method to penetrate the SC is proposed by
Bicosome, they develop a unique technology made of lipids with composition
similar to the lipid matrix of SC and that are structured in such a way that
very small disks are able by their size/composition to penetrate the SC.