Cream of Tartar

Cream of Tartar, known by its INCI name Potassium Bitartrate, is a naturally occurring acid salt that forms as a byproduct of wine fermentation. As wine settles, crystals of this compound form on the inside of casks and bottles, which are then collected, purified and ground into the fine white powder used in cosmetic and food applications.

In cosmetic formulation, Cream of Tartar is classed primarily as a stabiliser and texturising agent. It is most widely recognised for its role in bath bomb and bubble bar recipes, where it works alongside other ingredients to control the fizzing reaction and improve the final texture and hardness of the product. It is fully water soluble and mildly acidic, with a pH typically in the range of 3.5 to 5.

Unlike many ingredients on this site, Cream of Tartar is not primarily used as a skin conditioning or active ingredient in leave on skincare or haircare formulations. Its role sits firmly within bath product formulation, where its binding and stabilising properties are the main reason formulators reach for it. For anyone building a bath bomb or bubble bar range, it is considered a foundational ingredient alongside citric acid and sodium bicarbonate.

Cream of Tartar is used in bath bomb and bubble bar formulation because of the specific effect it has on texture and structure. When added to a bath bomb recipe, it helps harden the finished product and reduces crumbling, which matters both for the look of the product and for how well it survives shipping and handling before use.

In bubble bars and bath cookies, Cream of Tartar contributes a lighter, airier texture, helping the mixture bind together while giving the finished bar a fluffier consistency than it would have without it. This binding effect is a common reason formulators include it even in recipes where fizzing is not the main goal.

Its mild acidity also plays a role in the classic bath bomb reaction, working alongside citric acid to interact with sodium bicarbonate once the product meets water, contributing to a more controlled and longer lasting fizz. For a new brand formulating bath bombs or bubble bars, Cream of Tartar is a well established, low cost ingredient that directly improves the performance and durability of the finished product, rather than one added purely for a marketing claim.

Cream of Tartar is added as a dry powder during the mixing stage of bath bomb or bubble bar production, blended in with the other dry ingredients before any liquid or oil components are introduced. It is fully water soluble, so it is important to keep it away from moisture during storage and mixing until the formulation is ready to be moulded.

In bath bombs, Cream of Tartar is typically used at around 2 to 5 percent of the total formulation, usually alongside citric acid and sodium bicarbonate in a ratio that controls both the hardness of the bomb and the strength of the fizzing reaction. In bubble bars and bath cookies, it can be used at similar levels, primarily for its binding and texturising effect rather than for fizz.

Because Cream of Tartar reacts with moisture, it should be stored in a cool, dry place in an airtight container away from humidity. When formulating, it is worth testing different ratios of Cream of Tartar to citric acid and bicarbonate in small batches, since small changes in this balance can noticeably affect how hard the finished bomb is and how it behaves in water.

The main benefit of Cream of Tartar in cosmetic formulation is the improvement it brings to the structure and durability of bath bombs and bubble bars. It helps the finished product hold together and resist crumbling, which is a common issue in bath bomb formulation, particularly during shipping or handling before use.

It also contributes to a better fizzing performance when used alongside citric acid and sodium bicarbonate, helping to produce a more controlled reaction once the product hits water, rather than a fizz that is too fast or too weak.

In bubble bars and bath cookies, Cream of Tartar helps create a lighter, fluffier texture, which affects both the tactile feel of the product and how easily it breaks apart or dissolves when used.

Cream of Tartar is also a naturally derived ingredient, being a byproduct of winemaking rather than a synthetically manufactured additive, which supports formulations positioned around natural or minimally processed sourcing. It is widely recognised as safe for cosmetic use and is generally well tolerated on skin, though as with any new raw material, patch testing is advisable for sensitive skin types.

Cream of Tartar is almost always used alongside other core bath bomb and bubble bar ingredients. Consider pairing it with:

• Citric Acid, the key acid component that reacts with sodium bicarbonate to create the fizzing effect in bath bombs
• Sodium Bicarbonate, the alkaline base that reacts with citric acid and Cream of Tartar to produce fizz
• Kaolin Clay, often added to bath bombs for a smoother, silkier finish on the skin
• Witch Hazel, sometimes used as a light binding liquid in bath bomb moulding