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Pharma said:

It may. As said, all depends on the context… and your definition of ‘potency’.

I’ll rephrase the question.
Imagine I have a solution of salicylic acid and sodium citrate in water with pH, e.g. 5.0. If I apply this on skin how it will work? As salicylic acid and sodium citrate would work, or as sodium salicylate and citric acidsodium citrate would work?

All I want to understand if salicylic acid looses it properties when dissolving it that way.

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Pharma said:

Mixing salicylic acid with betaine in water results in betaine salicylate (at a pH dependent degree).

Also, mixing salicylic acid with sodium citrate (mono-, di-, or tricitrate doesn’t matter) results in sodium salicylate and citric acid (or a corresponding citrate). Again, the degree depends on pH and molar ratio.

In the end, all that matters is pH which turns salicylic acid into a more or less water soluble salt and thereby allows for easier dissolution. In low % aqueous or even anhydrous preparations wherein salicylic acid is soluble, production of salicylate salts results (for most cosmetic ingredients) in a reduced solubility.

Does it mean that salicylic acid looses it’s potency when dissolving it that way (because now it’s not the acid, but salt)?

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Paprik said

I do wash my hair everyday, but a lot of women do not. Yet, they can still have not-oily hair for days

isn’t it because they have long hair so the sebum evenly spreads? Whereas you, probably, has short hair, so it gets greasy quicker

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Hello, My name is Dima and I am from Ukraine. I am a software developer, but I have an interest in understanding formulations (as a hobby). I am also formulating some simple products for myself (just water-based simple serumstoners, no creams or fancy stuff).

So thank you all for the info provided on the forum and your answers to my questions, I really appreciate this.

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@grapefruit22
I am sorry if my messages look too harsh (as Perry says, it is easy to be misunderstood in text), I didn’t want to attack you in any way. English is not my native language, so I probably use wrong words sometimes and they look offensive, sorry if so.

grapefruit22 said:

You mean all the few you selected were about animals? It’s not true that all or even most of them were such kind of study

If you can provide a study from that list which is relevant - I would really love to discuss it. I found only one done on 4 pieces of human skin and it has a note that results might be irrelevant due to small number of trials.

I also checked the one with hydroquinone and have some doubts on it:
1. Only 16 women. I don’t think math would say it is statistically representative
2. These women were using Vitamin C on one part of the face and hydroquinone on other. They were covering whole face with a SUNSCREEN, So basically the comparison was Ascorbic acid + sunscreen with hydroquinone + sunscreen. How we can be sure it’s ascorbic acid helps but not the sunscreen? There should be 3rd group which is wearing ONLY sunscreen. Although it’s not included because results might be unpleasant (what if just sunscreen gives better results that combination of it with vitamin c or hydroquinone?)
3. Are we sure that brightening effect is based on Vitamin C special properties but not on pH and acidity? Are we sure that any other AHA acid with such percentage rate (15%) and pH value (around 3.5) won’t perform same, better?

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@Perry Agree, but do you think ascorbic acid could oxidize and degrade already in the skin during night or two and give the stain?

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grapefruit22 said:

You can check the mentioned studies and see if they are convincing.

As I said, I already took a quick look at some of the studies mentioned in the article and all of them are done on animals. It is not cool to throw in huge list of studies and say “the truth is somewhere there”. If you have a convincing one - show it, don’t expect people to go through each of them instead of you.

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grapefruit22 said:

The second article had 70 references to publications, none of them was convincing?

Actually, I made a quick glance at studies provided in the article and found none to be  done on humans, most of them are made on animals, which is not convincing.
Could you provide a specific study which is done on statistically meaningful number of humans with well-defined methodology?

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1. You didn’t read my questions carefully. I am not declining the fact that ascorbic acid evens skin tone. Although it seems it doesn’t do it in the way I expect. I expect it to fight hyperpigmentation and reduce dark spots, but it seems ascorbic acid just gives a small shade of fake tan which visually hides the issue rather than treating it.

2. I am talking exclusively about ascorbic acid, not derivatives.

3. I’m not surprised you get instant brightening of the face. Most serums have huge percentage of ascorbic acid, which is white powder. If you put such amount of zinc oxide you would get the same whitness. But in the long run ascorbic acid just stains the skin (IMHO)

4. You can read the same amount of feedbacks from people who say same thing as I do - Vitamin C makes skin orange and just gives a fake tan (which makes skin look even, but it’s only visual effect)