Citric Acid, Monohydrate, 1 kg

Citric acid serves primarily as a pH regulator in cosmetics. A few tenths of a percent is enough to shift a toner, shampoo or emulsion from the neutral or alkaline range into the mildly acidic range that corresponds to the skin's natural pH. In addition, it binds metal ions from water and raw materials, supporting product stability, and in bath bombs it forms a pair with baking soda that begins to fizz on contact with water.

It is supplied as a monohydrate in cosmetic and food-grade quality. It dissolves in water, so it belongs in the water phase or is added at the end of production as a diluted solution.

What it does in the formulation

• pH regulator – lowers the pH of aqueous and emulsion systems. It is used wherever the pH after combining the raw materials comes out higher than the product requires, for example after adding surfactants, extracts or certain emulsifiers.
• Buffering component – together with sodium citrate it forms a citrate buffer that keeps the product's pH at the set value even after the addition of further ingredients or during use.
• Chelating agent – binds calcium, magnesium and iron ions that enter the product with water and raw materials. Free metal ions reduce the foaming ability of surfactants, accelerate changes in fragrance and colour, and decrease the effectiveness of preservation.
• Antioxidant support – by binding metals, it slows oxidative changes in the oil phase. It is therefore often combined with tocopherol or rosemary extract, whose effects it complements.
• Exfoliation and brightening – it belongs to the fruit acids (AHA). At acidic pH it promotes gentle shedding of dead skin cells and a more even, brightened complexion. The result depends on the dose, pH and duration of skin contact.

Use in formulation

For pH adjustment, a dosage of 0.1 – 2% is recommended; an ordinary emulsion or shampoo will manage with the lower half of this range. The recommended pH range of the finished product is 3.0 – 6.0, processing up to 80 °C. The acid is added to the water phase, to the cooling phase, or additionally at the end when the product is finished and the pH is only being fine-tuned.

In bath bombs it is the main ingredient alongside baking soda, and dosing here is not governed by pH adjustment percentages. The mixture is combined dry and moistened only minimally to prevent the reaction from starting prematurely.

In cold-process soap it neutralises part of the sodium hydroxide. The resulting sodium citrate binds calcium from hard water, thereby reducing soap scum formation. The amount of lye in the recipe must therefore be increased proportionally; otherwise the soap will come out softer than planned due to a higher excess of fat.

In hair care it is used for an acidic rinse after washing or to adjust the pH of conditioners. A mildly acidic environment closes the hair cuticle, so hair combs more easily after drying and has more shine.

Suitable for products such as

• toners, facial waters and hydrating sprays, where pH is set close to the skin's value,
• creams, milks and serums as a final pH adjustment in the cooling phase,
• shampoos, shower gels and bath foams, where it also improves foaming in hard water,
• acidic hair rinses and conditioners,
• bath bombs, effervescent salts and effervescent bath tablets,
• cold-process and hot-process soaps,
• mouthwashes and toothpastes as a pH regulator,
• decorative cosmetic products with an aqueous phase.

What is good to know

Low pH affects viscosity. Some thickeners lose thickness in an acidic environment, so with gel products adjust the pH before thickening or choose a thickener that is stable in an acidic environment. Citric acid and citrates are also electrolytes; a higher dose may thin or conversely thicken a surfactant system. After adding, allow the product to stabilise and reassess the viscosity.

Preservatives based on organic acids (potassium sorbate, sodium benzoate) work only in an acidic environment. Without pH adjustment with citric acid, preservation in such formulations does not function.

For leave-on products with a pH at the lower end of the range, we recommend testing compatibility on a small area of skin. The exfoliating effect becomes more pronounced as pH decreases and dosage increases.

Citric acid and sodium citrate

Both raw materials share the same origin but behave in opposite ways. Citric acid lowers pH, while sodium citrate slightly raises it and binds metals without acidifying the product. They often work together: the acid sets the target pH and the citrate holds it in place as a buffer. Citrate is chosen for chelation without a pH shift; acid for acidifying the product.

Frequently asked questions