Tetrahexyldecyl Ascorbate (vitamin C)

What is it? Tetrahexyldecyl Ascorbate is a stable, oil-soluble form of vitamin C, offering the benefits of L-ascorbic acid without the formulation challenge.

Mine is from Simply Ingredients and their product page has lots of great information; check it out to learn more.

INCI Tetrahexyldecyl Ascorbate
Appearance Clear oily liquid
Usage rate 0.5–20% (I’ve found upper limits ranging from 2 to 20%; the listed range is from Simply Ingredients)
Scent Nothing noticeable
Approximate Melting Point Liquid at room temperature
Solubility Oil
Why do we use it in formulations? Like L-ascorbic acid, Tetrahexyldecyl Ascorbate can help reduce pigmentation and age spots, increase collagen synthesis, and is a powerful antioxidant.

Unlike L-ascorbic acid, Tetrahexyldecyl Ascorbate is oil soluble (so it can be used seamless in anhydrous formulations) and it’s stable, so you don’t have to worry about pH and oxidization when formulating with it. It’s also less irritating than L-ascorbic acid.

Do you need it? No, but I’d consider it a great luxury ingredient.
Refined or unrefined? Tetrahexyldecyl Ascorbate only exists as a refined ingredient.
Strengths It works and it’s easy to work with!
Weaknesses It’s really expensive.
Alternatives & Substitutions A different oil-soluble format of vitamin C like L-Ascorbyl Palmitate would be a good place to start.

Depending on the formulation you could look at other forms of vitamin C, like Sodium Ascorbyl Phosphate, Magnesium Ascorbyl Phosphate, or L-ascorbic acid.

Different formats of vitamin C will have different formulation requirements and usage rates, so make sure you are doing your research to ensure compatibility, safety, and success.

Depending on the formulation and role Tetrahexyldecyl Ascorbate is meant to play in it, you could also try replacing it with a different ingredient (or ingredients) that offer similar benefits. For example, Niacinamide (Vitamin B3) also has skin brightening benefits, and Tocopherol (Vitamin E) is a great antioxidant.

How to Work with It A pH of 3–6 is recommended for hydrous formulations. Avoid prolonged heat, Sandream Impact recommends 80°C as the maximum temperature.
Storage & Shelf Life Stored somewhere cool, dark, and dry, Tetrahexyldecyl Ascorbate should last 3 years.
Tips, Tricks, and Quirks According to Sandream Impact, “THDA [Tetrahexyldecyl Ascorbate] is approved as a quasi-drug in Korea at 2%, and in Japan at 3%.”
Recommended starter amount 30g (1.06oz)
Where to Buy it  Buy it from an online DIY ingredient supplier; mine was a gift from Simply Ingredients.

Some Formulations that Use Tetrahexyldecyl Ascorbate

Ascorbic acid (vitamin C)

What is it? Ascorbic acid is also known as vitamin C; it’s a potent antioxidant with fabulous brightening + collagen-boosting skincare benefits.
INCI Ascorbic acid
Appearance Crystalline white powder; much like table salt or sugar.
Usage rate 3–25% (source)
pH 2.2–2.5 (5% solution in water) (source)
Solubility Water soluble
Why do we use it in formulations? Vitamin C helps increase collagen production, reduce excess pigment/brighten the complexion, boost healing, and counter UV damage. It’s an amazing, well-studied skincare active. Learn more about it with this great post from LabMuffin!
Do you need it? No, but if you’re interested in formulating high-performance skincare products it’s definitely something to consider.
Refined or unrefined? Pure ascorbic acid only exists as a refined ingredient.
Strengths Ascorbic acid is a well studied, highly effective skincare active. It’s also pretty inexpensive!
Weaknesses Ascorbic acid is very unstable in water, breaking down in less than a month.

Ascorbic acid can also be irritating to the skin, with higher concentrations having a higher irritation potential. More isn’t necessarily better; start with a lower concentration and work your way up if desired/required.

Alternatives & Substitutions Vitamin C derivatives like Tetrahexyldecyl Ascorbate, Ascorbyl Palmitate, magnesium ascorbyl phosphate, sodium ascorbyl phosphate, and L-ascorbyl palmitate can be good alternatives. These derivatives can be oil or water soluble, so make sure the solubility is compatible with your formulation. These derivatives are typically more stable than ascorbic acid and less irritating, but they’re generally not as effective and they’re usually more expensive ($7/oz vs $20/oz).

You can also look at using other ingredients that also offer similar skincare benefits (you may want to blend two or three ingredients). Niacinamide (Vitamin B3) would be my top choice as it has both skin-brightening and collagen-boosting effects. N-Acetyl Glucosamine (NAG) also offer skin-brightening benefits. Vitamin E is a great antioxidant.

How to Work with It When formulating with ascorbic acid and water you’ll need to include ingredients that stabilize it and/or plan to use it within a week or two. For a formulation including stabilizers, check out this Skinceuticals-Dupe Vitamin C serum from The Acid Queen. For an easier, use-it-up fast formulation, Lab Muffin has shared a 5-minute DIY Vitamin C Serum formulation.

As ascorbic acid is very acidic you’ll need to raise the pH of your formulation to around 3.5 using something basic; a 10% sodium hydroxide solution works well for this job.

You can also use ascorbic acid in anhydrous formulations, like ones sold by The Ordinary and Paula’s Choice. Since ascorbic acid won’t dissolve in an anhydrous base you’ll want to use a finely powdered version for a smooth finished product; you can purchase extra-fine versions or use a coffee grinder/mortar & pestle.

Storage & Shelf Life Lotion Crafter recommends purchasing ascorbic acid in amounts you can use up in 3–4 months. Learn more here.
Tips, Tricks, and Quirks Don’t use ascorbic acid products with copper ions or benzoyl peroxide as those ingredients will deactivate the vitamin C (source: LabMuffin).
Recommended starter amount 30g (1.06oz)
Where to Buy it Buy it from an online DIY ingredient supplier or Amazon. This is an ingredient that you can purchase as a supplement, just be sure to choose a pure powdered version rather than pressed tablets (those will have some other ingredients in them to bind the tablet together). The powdered L-ascorbic acid that The Ordinary sells will also work, and is reasonably priced for a small amount.

Some Formulations that Use Ascorbic Acid

Lactic acid

What is it? Lactic acid is an alpha hydroxy acid that is used for pH adjusting and for creating skincare formulations that chemically exfoliate the skin. Humans have been embracing lactic acid in skincare for centuries—lactic acid is part of the magic of a milk bath! Lactic acid is considered to be more gentle than its sister AHA, glycolic acid.

Health Canada regulations stipulate that all formulations that contain 3% or more lactic acid must bear these warnings:

  • “Use only as directed.”,
  • “Avoid contact with the eyes.”,
  • “If irritation persists, discontinue use and consult a physician.”,
  • “It is recommended that prior to exposure to the sun, users cover areas where AHAs have been applied with sunscreen.”,
  • “Contact of the product with the skin must be of limited frequency or duration.”

Lactic acid is part of the skin’s natural moisturizing factor (NMF), compromising 10–12%.

INCI Lactic acid
Appearance It is often sold as an 88% or 90% liquid solution; this is is a clear, slightly viscous fluid.
Usage rate For pH adjusting, generally less than 1% (though usually less than 0.5%). For chemical exfoliation, no more than 10%, though I’d recommend starting with less.

Health Canada regulations limit non-professional use of lactic acid to 10%, with a pH equal to or greater than 3.5. Any concentrations higher than 10% are limited to professional use.

“The CIR Expert Panel evaluated the scientific data and concluded that … Lactic Acid… [was] safe for use in cosmetics and personal care products at concentrations of 10% or less, at final formulation pH of 3.5 or greater, when formulated to avoid increasing sun sensitivity or when directions for use include the daily use of sun protection.” (Source)

Scent Sour, tangy
pH 0.6
Solubility Lactic acid is water soluble.
Why do we use it in formulations? Lactic acid lowers the pH of our formulations; it is often used at very low concentrations to adjust pH.

In higher concentrations lactic acid acts as a chemical exfoliant and skin care active.

Some skincare benefits from using lactic acid include:

Do you need it? No, but it is very useful if you are interested in making high-performance skin care.
Refined or unrefined? The lactic acid used in cosmetics and skin care is always a refined product.
Strengths Potent pH adjustor, occurs naturally in the skin, mild as far as acids go.
Weaknesses Like all potent ingredients, it requires care when formulating with it.
Alternatives & Substitutions Other pure acids (citric acid is typically the most readily available) will work for pH adjusting, though it won’t be a 1-for-1 swap; you’ll need to test and adjust the formulation using the new acid.

Other alpha hydroxy acids like mandelic acid and glycolic acid can also be used to create exfoliating products. As with pH adjusting, this will not be a 1-for-1 swap; you will need to test and adjust the pH of the formulation to ensure it is safe.

How to Work with It Wear gloves; concentrated lactic acid is very acidic.

I’d say you need a digital pH meter to formulate products where lactic acid is a feature ingredient. The precise pH of the formulation is very important for safety, and strips aren’t very precise.

Lactic acid can be hot or cold processed.

Ensure the final pH of the product is 3.5 or greater: if you are creating an exfoliating product you will almost certainly need to raise the pH of your formulation (I use a 10% sodium hydroxide solution). As lactic acid has a pKa of 3.86, I recommend aiming for a pH close to 3.86 for optimal performance. Learn more about pKa with this fabulous article from Lab Muffin!

If following a formulation that calls for lactic acid, make sure you pay attention to the concentration called for in the formulation. If yours is a different concentration, adjust the lactic acid and water content of the formulation if required to end up with the same final percentage of lactic acid.

Storage & Shelf Life Stored somewhere cool, dark, and dry, lactic acid should last at least 2 years.
Tips, Tricks, and Quirks I recommend re-packaging your lactic acid in a glass bottle with a dropper top lid for easy dispensing.

You can create a buffer with lactic acid and sodium lactate in a 1:2 ratio, which should hold a formulation around a pH of 4. Learn more here.

Lactic acid does occur in milk, but cosmetic grade lactic acid is synthesized (and vegan).

Do not use lactic acid (or other AHAs) together with retinol. Do not apply to irritated skin.

Recommended starter amount 30mL (1fl oz) for pH adjusting; 60mL if you intend to use it as a chemical exfoliant.
Where to Buy it  Buy it from an online DIY ingredient supplier or Amazon.

Some Formulations that Use Lactic acid

Salicylic acid

What is it? Salicylic acid is a beta hydroxy acid that is primarily used as a chemical exfoliant in skincare. It’s very common in anti-acne products as its oil-soluble-ness means it is able to get into pores and break down clogs and other gunk that can lead to pimples and congestion.

Learn heaps more about salicylic acid with this fantastic post from Simple Skincare Science: Salicylic Acid for Skin Explained (34 Studies): Everything You Need to Know! Some key, interesting points from the post:

  • Salicylic acid is not pH dependent.
  • A 2% solution used for 3.5 weeks did not increase susceptibility to sunburn.
  • Start low and go slow!
INCI Salicylic acid
Appearance Fine white crystalline powder
Usage rate 0.1–2%.

Salicylic acid is a restricted ingredient in Canada with a maximum usage rate of 2% in cosmetic products.

Scent Nothing noticeable
Approximate Melting Point 159°C (318°F)
pH 2.4
Solubility Salicylic acid isn’t terribly soluble:

Source: Making Cosmetics

Why do we use it in formulations? Salicylic acid is anti-inflammatory, prevents & addresses clogged pores, improves skin cell turnover, chemically exfoliates, and has anti-bacterial properties.
Do you need it? No, but if you are interested in anti-acne skincare it’s a good ingredient to have.
Refined or unrefined? Salicylic acid only exists as a refined ingredient. You can purchase less potent white willow bark solutions and extracts; refer to supplier documentation for usage (here’s an example).
Strengths Effective, proven anti-acne active ingredient.
Weaknesses Salicylic acid can be irritating if over-used. Start with low concentrations and infrequent (2–3x/week) use. Increase usage slowly.
Alternatives & Substitutions Allantoin is also anti-inflammatory and keratolytic, so that could be a potential option.

Alpha hydroxy acids like lactic acid and glycolic acid are also chemical exfoliants, though they are water soluble.

How to Work with It Wear a mask, eye protection, and gloves when working with pure salicylic acid as it is both potent and floaty.

Do not exceed 2% usage rate.

You’ll need to include an adequate amount of solvent to dissolve the salicylic acid; how much is enough will depend on what solvent you’re using.

Aim for a final pH of no less than 3.2–3.8 in hydrous formulations. Salicylic acid is not pH dependent (source).

Storage & Shelf Life Stored somewhere cool, dark, and dry, salicylic acid should last at least five years.
Tips, Tricks, and Quirks Do not use salicylic acid if you’re allergic to aspirin.
Recommended starter amount 30g (1.06oz)
Where to Buy it  Buy it from an online DIY ingredient supplier or Amazon.

Some Formulations that Use Salicylic Acid


What is it? L-Arginine is an amino acid with a basic pH—it’s useful for boosting the pH of our formulations.

It has moisturizing, skin conditioning, and barrier boosting properties, but if used at pH-adjusting amounts those benefits are unlikely to be noticeable in a finished product. The formulations I’ve found that use it as an active ingredient use it at 0.5–2%. Your mileage may vary, though! Depending on the formulation you may be able to work in enough L-Arginine to get skin benefits and a perfect pH.

INCI Arginine
Appearance White crystaline powder
Usage rate As needed to get the pH of your formulation where you want it; generally less than 1%.
Scent Nothing noticeable at pH-adjusting levels.
pH A 10% L-Arginine solution has a pH between 10.5–12.
Solubility L-Arginine is water-soluble.
Why do we use it in formulations? L-Arginine is used to raise the pH of our formulations; I find I’m most likely to need it when working with acid-based natural preservatives that dramatically lower the pH of a formulation.
Do you need it? No, but you should have something to raise the pH of your formulations and this L-Arginine is a good choice if you can get it.
Refined or unrefined? L-Arginine only exists as a refined ingredient.
Strengths An easy, gentle ingredient for raising the pH of our formulations.
Weaknesses It’s not terribly easy to find.
Alternatives & Substitutions A 10% NaOH (lye) solution or triethanolamine will work, but not in the same amounts—if you’re following a formulation that includes L-Arginine to adjust the pH you’ll have to test and adjust with the new base/pH raising ingredient.
How to Work with It L-Arginine isn’t super strong, so you can add the straight powder to some formulations, or make a dilution—whatever works for each formulation. I keep a 10% solution and the pure powder on hand.
Storage & Shelf Life Stored somewhere cool, dark, and dry,
Tips, Tricks, and Quirks Cosmetic grade L-Arginine is not the same as food, dietary supplement, or pharmaceutical grade. I’m unsure if L-Arginine purchased from the drug store would be a good workaround if you can’t purchase cosmetic grade L-Arginine.
Recommended starter amount 30g (1.06oz)
Where to Buy it I’ve only found cosmetic grade L-Arginine at Skin Chakra (Germany) and Essential Wholesale (USA).

Some Formulations that Use L-Arginine