Acidic Scar healing lotion curdled under cooldown. Help me fix my recipe

Zink

Rough recipe that should have enough clues

Water phase  ~50%

Oil phase ~50%

Water Phase: Water, Sodium Lactate, 5% Lactic Acid.

Oil Phase: 7% Ewax, Tamanu Oil, Hemp Seed oi, Shea Butter, 5% Salicylic Acid, 5% Lipoic acid, Sulfur, Stearic acid, Vitamin E. 

Cooldown: Zinc Oxide

The oil phase separated on its own, and when mixed with the water phase under high shear mixing and cooled, it curdled. I poured of a small amount of liquid that had separated from the curdle, and it formed a lotion again (not a stable one but alas).

Just wondering which ingredients are incompatible with each other or just low pH? Almost looked like the addition of lipoic acid caused the salicylic acid to precipitate! Or maybe the acids aren't comp with all of the fats..

DavidW

I don't think Salicylic is soluble in those oils

Zink

Right, hard to find good data on solubility, maybe I'm looking the wrong places. If going pure oil I'll need a way to keep different oils from separating, not sure how that's done!

Found this paper: 1 part salicylic acid is soluble in 45 parts olive oil and interestingly only 7 parts castor oil, i.e. castor oils is a much better choice.

http://archderm.jamanetwork.com/article.aspx?articleid=520332

Ruben

I think 7% ewax is not enough emulsifier for a 50% oil phase

MakingSkincare

What is the INCI of your ewax and also what preservative did you use?

DavidW

50% oil phase is huge.  Salicylic acid will go into SD Alcohol or hot propylene glycol.  You can try other glycols too.  However, with so much water it may drop out over time.

mikebavington

EWax is Cetearyl Alcohol and Polysorbate 60, right? It might be better to use a separate and distinct low hlb emulsifier to compliment the Polysorbate 60 in your EWax component and therefore reach the right HLB number for your oil phase. If something is separating, it means your emulsifiers arent working properly, in most instances. I thought Cetearyl Alcohol was more of a thickener as opposed to a straight emulsifier.

I have read that Cetearyl Alcohol can be used as a co-emulsifier when incorporated at rates greater than 5%, so you might want to get the two ingredients - Cetearyl Alcohol and Polysorbate - separately, and then add more Cetearyl Alcohol into your formula to get to that 5% threshold, while still continuing to use Polysorbate 60 as you desire.

MakingCosmetics distributes both of these ingredients. There website is:

www.makingcosmetics.com

Zink

Yes, Ewax INCI: Cetearyl (Cetyl+Stearyl) Alcohol and Polysorbate 60. And yes, 7% is on the low side, good suggestion to add more low HLB emulsifier. 

But for the next edition I'll do an anhydrous version with a high % castor oil and add thickener to keep the oils together, any ideas on that? Cetyl Alcohol ? Beeswax? 

@DavidW how many g/l can you dissolve in SD alcohol or hot propylene glycol? And does it remain in solution as the PG cools?

For preservative, Optiphen PLUS or Neodefend (lotioncrafter) probably. 

MakingSkincare

Optiphen plus can cause emulsion instability so that together with too little emulsifier could be causing your curdling issue. I have some formulation tips on my preservative page http://makingskincare.com/preservatives/ to help with optiphen.

I wouldn't add a low HLB emulsifier to the ewax unless your required HLB actually needs it. 

Lotionpro 165 is a good, reliable emulsifier blend which is great with acids.

Zink

In this case I decided to choose preservative after making the base lotion,  as the base could change so much, turned out to be the right decision as I'm switching to anhydrous (for now).

Zink

I modified a SA solubility  spreadsheet BTW: https://docs.google.com/spreadsheet/pub?key=0AppNaehx8mQqdHo5dmpZUWpDOU5SWkVVZ1VQMFpaRnc&single=true&gid=18&output=html

DavidW

"how many g/l can you dissolve in SD alcohol or hot propylene glycol? And does it remain in solution as the PG cools?"  Not sure, easily find out with Google. 

IT does stay in when PG is cooled.

Zink

For reference you can dissolve 220 gram SA in 1L propylene glycol at RT.

Chemist77

SA has a very good solubility in MPG and as pointed out by Zink it has some solubility in Castor oil and Olive oil too. But the focus should be to keep it solubilized when these solutions (in different vehicles) are added to the emulsion which has good quantity of water as well.

Unknown

Not sure, Brand new here. Is there a more recent thread, and a way I might find it, about the solubility of salicylic acid in alcohol and propylene glycol with water and witch hazel then added?  Don't want to offend or break rules. 

MarkBroussard

Your problem is that Stearic Acid (both in the EWax and the additional Stearic Acid your adding separately) needs a base to neutralize it to form the emulsion.  So, you'll need to add 0.2% NaOH to your aqueous phase to form the emulsion. 

Then, once this emulsion forms, add the Salicylic Acid dissolved in 1,3-Propanediol during cool down.

And, 50% Oil phase is crazy high ... you should drop that to 20% max.

johnb

Not sure, Brand new here. Is there a more recent thread, and a way I might find it, about the solubility of salicylic acid in alcohol and propylene glycol with water and witch hazel then added?  Don't want to offend or break rules. 

You can search for old threads via the search facility at top, right of the page.

To be more specific re. your question, as the variables in mixed (3 or 4) solvent systems are so wide the best, perhaps only, way to determine salicylic acid solubility is to experiment yourself.

Doreen

@MarkBroussard ;

Another thread exhumed (2014)

johnb

@MarkBroussard ;

Another thread exhumed (2014)

But with a new twist!

The new section ought to have a new thread but I have made a reasoned response, I think.

Doreen

@johnb
It can be a bit confusing sometimes, I don't always see in time that it's old. But you're right! Your answer came in handy for myself aswell (SA solubility finding out by experimenting).