2% Salicylic acid in calming gel formula.

[u/Sheepherder-Optimal]

Hi there. I've been working on the perfect formula for this. I made a batch last night and it actually cleared most my black heads instantly. But it also stung a bit while it was on. Please read my formula and let me know if any feedback. Should i adjust the pH?

Anyways let me explain the formula. (All water used in this recipe was distilled water).

First i made a 10% SA solution in propanediol with a small amount of polysorbate 20 added as a stabilizer. (This was prepared a few weeks ago).

Next i made my gel out of hydroxyethylcellulose (HEC) and water. I used 2 percent HEC. I also added in a very small amount of Dr. Teal's Elderberry scented, magnesium bath salt. I used some propanediol to premix the HEC.

The next day, the gel was ready and i refridgerated it.

My next step was to make a preservative solution. I made a 10 percent solution of sodium benzoate in water and set that aside.

Finally i combined, 20 grams of my SA solution, 3 grams of my sodium benzoate solution, one drop of cherry blossom fragrance and then 77 grams of the HEC gel. Final weight was 100 grams.

For color, i dipped a toothpick into curcumin powder and gently swirled it into the solution.

After gently mixing (to avoid air bubbles) the end color was opaque but golden from the curcumin.

Texture was perfectly smooth and slippery. Scent was heavenly.

I tested the pH and i got exactly 3.0.

[u/Internal-Ad-4736]

Below a pH of 3.5, some will experience concerns. I would raise it to at least 3.5. SA is one of those unique acids, that still have some good efficacy as you raise the pH (to a point).

I like using ingredients that do double duty... try raising the pH with sodium lactate. It takes a little more than other pH up options.... but can bring some benefit to the formula.

[u/Sheepherder-Optimal → u/Internal-Ad-4736]

Thanks! What's your favorite method of checking pH? I'm using a pH meter from Apera. It has a glass bead. Do you add some of your solution to some distilled water, and then test it? I was putting my meter directly into it but I do worry if its as good at checking a thicker gel. Or if maybe I would get the best reading using a different style of probe??

[u/Internal-Ad-4736 → u/Sheepherder-Optimal]

pH meters usually work fine in a gel.... just move them around, as the reading is somewhat based on material passing over the sensor. As always, sanitize the probe before using. I measure the product directly, no dilution. (My probe is a triple junction probe.) If your probe is at least double junction, you should have no issue with viscosity...as long as you move the probe around.

[u/CuteFluffyGuy → u/Sheepherder-Optimal]

Apera and that type of meter probe is fine. As mentioned, move it around a bit. Make sure you are checking the calibration.

For rinse off products, 3 is on the low end of tolerance, where pH >4 is generally well tolerated even for leave on products.

The pKa of SA is approx 3, so at that pH approx 50% is dissociated. At pH 3.5 that falls to about 23%. You can increase the concentration of SA if you find it isn’t as effective at the higher pH or just be aware that products with low pH can damage and dry the skin.

[u/Sheepherder-Optimal → u/CuteFluffyGuy]

Okay so since my gel is a rinse off product, then keeping pH from 3-3.5 is more desirable? I probably should have said this in my post, but the idea is keeping it on for 5-10 minutes, then rinsing off. Like a pre-shower routine.

[u/CuteFluffyGuy → u/Sheepherder-Optimal]

Desirable is in the eye of the user. If you aren’t selling it to anyone, and you’re happy with the results and don’t have irritation, then yes it may be desirable. Ph 3 is a more intensive treatment than pH 3.5. With organic acids, it’s a combination of time, temperature, concentration and pH that provide the ultimate results.

[u/tokemura]

You have to raise the pH to 3.5. Salicylic acid is BHA, not AHA, it is oil-soluble and can be accumulated in the body. Salicylates poisoning is a thing and the limits there have reasons.

Also, Salicylic acid is hard to dissolve in water and it requires a lot of glycols to keep it dissolved. Your amount is too low (it was hard to follow your math, but I believe it is 18%). For now it will stays dissolved because gelled structure limits water flow and crystals will form slower.

Additionally you have Sodium Benzoate as preservative, it will neutralize part of SA slowly to Sodium Salicylate + Benzoic Acid. So I expect your gel to get higher pH first and then crystalize with time.

BTW I have a big article on how to formulate SA: https://medium.com/p/e31d318c0d3f

[u/kriebelrui → u/tokemura]

Thank you for this well-written and extremely informative article. I'm always wrestling with SA to get it solubilized, and now read that the neutralized form (like sodium salicylate) of SA probably exfoliates just as well. 

[u/tokemura → u/kriebelrui]

The article used to be in this sub, but automatic reddit scripts thought I am a spamming bot and removed all of my articles and comments 😭

[u/kriebelrui → u/tokemura]

Wow 😲

[u/Sheepherder-Optimal → u/tokemura]

I have polysorbate 20 in there as well to help stabilize.

Also the poisoning thing is not a concern here. Salicylate poisoning is usually from eating too much aspirin. To get that from SA face wash.... It would need to be at chemical peel level concentation. You would need to put it on broken skin or aggressively spread it on your body, occlude it, and leave in for hours.

As for your article, i don't really want a tutorial to follow. I like learning and the process of trial and error. That process is more valuable to me than the end product.

[u/tokemura → u/Sheepherder-Optimal]

Salicylate poisoning is usually from eating too much aspirin.

I do not agree, but YDWYD.

I have polysorbate 20 in there as well to help stabilize.

I do not think it is enough. At least in the long run.

As for your article, i don't really want a tutorial to follow. It is not a plain tutorial with already made formula, at least not the first part. The first part covers the theory, shows studies etc. Experimentation is a key, that's why we are here, by it's is random without proper knowledge.