Cosmetic Grade 99%，Calcium thioglycolate CAS 814-71-1

What is calcium thioglycolate? How does it work? What are all its uses?

1. What is Calcium Thioglycolate? How does it work?

Calcium thioglycolate, also known as calcium mercaptoacetate or calcium 2-mercaptoacetate, is the calcium salt of thioglycolic acid (CAS 68-11-1). It is one of the most widely used thioglycolate salts in cosmetics, leather tanning, fine chemicals, and scientific research. Its molecular formula is:

C4H6CaO4S2 (Ca(OOCCH2SH)2, molecular weight approximately 222.30; CAS No.: 814-71-1; CAS No. for trihydrate: 14237-47-9)

It is a white or off-white crystalline powder at room temperature, with the characteristic pungent odor of thiols (mercaptoyl groups) (similar to rotten eggs/hydrogen sulfide). It is soluble in water (in appropriate amounts), and its aqueous solution is strongly alkaline (pH approximately 11-12). It is highly reactive and easily oxidized and deteriorated in air (the thiol group is oxidized to disulfide and becomes ineffective). It must be stored in a sealed, moisture-proof, and light-protected environment. Industrially, it is refined by reacting mercaptoacetic acid with calcium hydroxide to form a salt.

Structurally, calcium thioacetate consists of two thioacetate groups (-SCH2COO-) and one calcium ion (Ca2+). Each thioacetate group carries both a reducing thiol group (-SH) and a carboxylate group (-COO-): the thiol group acts as a "scissor" to break keratin disulfide bonds, the carboxylate group is responsible for forming a stable solid salt with the calcium ion, and the calcium ion provides a mild alkaline environment to the formulation. This is the structural basis for its use as an active ingredient in hair removal and perming products and as an industrial reducing agent.

Chemically, the most crucial property of calcium thioglycolate is the strong reducing power of its thiol groups: it can reduce and break the disulfide bonds (-SS-) in keratin, such as those in hair, nails, and wool, into two thiol groups (-SH), causing the keratin structure to disintegrate and the hair to soften and fall out. This reducing power is significantly enhanced under alkaline conditions (pH 10-12). Simultaneously, the thiol groups are easily oxidized by air to disulfide bonds (becoming ineffective), therefore the product requires the addition of antioxidants and sealed storage. It can also form complexes with metal ions such as iron, molybdenum, silver, and tin, exhibiting metal complexation and reduction color-developing abilities. Storage should be sealed, moisture-proof, protected from light, and kept away from oxidants.

From the perspective of its mechanism of action, calcium mercaptoacetate exerts its effects through the unique properties of "disulfide bond reduction + alkaline softening + calcium salt support + oxidative regeneration + metal complexation". The mechanisms of action in different applications are as follows:

1.Disulfide bond reduction mechanism (core mechanism)

The strength and toughness of keratin, such as hair, nails, and wool, come from a large number of disulfide bonds (-SS-) cross-linking. The thiol group (-SH) of calcium thioglycolate can reduce and break the disulfide bonds into two thiol groups (-SH), causing the originally hard and tight keratin structure to disintegrate and its mechanical strength to drop sharply. As a result, hair becomes soft and brittle and breaks easily when rubbed. This is the common chemical basis for hair removal, perming, and leather depilation (discovered by David Goddard in the 1930s).

2.Alkaline softening mechanism (keratin swelling)

Calcium thioglycolate aqueous solution is strongly alkaline (pH 11-12). The alkaline environment causes the keratin on the hair and skin surface to swell and loosen its structure, while significantly enhancing the reducing activity of thiol groups. This dual approach accelerates the softening and disintegration of keratin, which is why depilatory creams maintain a high pH and why lime-sulfide systems are used for depilation in leather tanning (cosmetic regulations limit the use of pH ≤ 12.7).

3.Calcium salt carrier mechanism (solid stability and paste formulation)

The calcium salt form allows thioglycolic acid to exist in a stable solid state, making it easy to formulate into creams and for industrial use. Calcium ions also participate in maintaining the alkaline buffer system of the formula. Compared with free acids and ammonium salts, calcium salts have relatively controllable irritation and good storage stability, making them one of the preferred salt forms for hair removal creams.

4.Oxidative regeneration mechanism (perming and styling)

Calcium thioglycolate is used in the perming process to break the disulphide bonds of the hair keratin to soften the hair before curling and shaping it. Next an oxidising agent such as hydrogen peroxide or bromate is added, which re-oxidizes the adjacent thiol groups to new disulphide bonds, locking in the curl shape, and producing a long-lasting perm or straight hair style.

5.Metal complexation and reduction colorimetric mechanism (analytical detection)

The divalent anion of mercaptoacetate can form stable complexes with metal ions such as iron, molybdenum, silver, and tin (e.g., ferrous iron reacts with mercaptoacetate to form reddish-purple ferric mercaptoacetate). This complexation colorimetric property can be used for the qualitative and quantitative detection of metal ions, which is the mechanism basis for its use as an analytical reagent.

In summary, calcium thioglycolate is a versatile thioglycolate-based fine chemical: as an active ingredient for hair removal, it softens and removes hair by breaking keratin disulfide bonds; as a hair perming reducing agent, it reshapes hair through a reduction-oxidation cycle; as an industrial reducing agent, it serves in leather tanning and fine chemical industries; and as a complexing reagent, it participates in metal analysis and detection. It is one of the most comprehensively used varieties in the thioglycolate family.

II. What are all the uses of Calcium thioglycolate?

1.Active ingredients in hair removal products (core application in the hair removal field)

Application Field: Personal care and hair removal

Corresponding Products: Hair removal creams, hair removal mousses/sprays, hair removal products for sensitive areas such as the face and bikini line, men's body hair management products

Applicability Principle: After applying hair removal products, the thiol groups of calcium thioglycolate penetrate the hair shaft, reducing and breaking keratin disulphide bonds, softening and embrittling hair from the root. After a few minutes, hair can be easily scraped off, achieving “root softening and painless hair removal”. It is the most classic active ingredient in depilatory creams, which have been used since the 1940s. Different formulations (creams/solutions/mousses/sprays) only differ in carriers. Formulators adjust concentration, pH and add soothing ingredients to control irritation for sensitive-area formulas and men’s products, while the core reduction mechanism remains unchanged. It also acts as an alkaline component in formulations, forming a buffer system with calcium hydroxide to maintain the required pH for hair removal (regulatory limits: concentration ≤5%, pH ≤12.7) and enhance thiol reduction activity.

2.Reducing agent for hair perming agents (cold perm solution) (hair industry)

Application Field: Hair styling, perming

Corresponding Products: Cold perm lotion, perm solution, curl styling products

Applicability Principle: In the first stage of cold perming, a reducing agent breaks disulphide bonds inside the hair shaft to soften hair and make it malleable. Thioglycolate (calcium/ammonium salt) acts as the active reducing agent in this step. Once hair is softened and curled, an oxidising agent rebonds and sets the curls, delivering a long-lasting curly effect.

3.Hair straightening and styling agent ingredient (hair care industry)

Application Field: Hair styling, hair straightening

Corresponding Products: Straightening cream, straightening agent, straightening treatment

Applicability Principle: The underlying principle of hair straightening is similar to perming. Calcium thioglycolate reduces and breaks disulphide bonds to relax frizzy and curly hair. After straightening, oxidants re-crosslink keratin and fix the shape, “locking” straight hair, reducing frizz and achieving long-lasting straightness. This is the fundamental principle of chemical hair straightening products.

4.Nail softening agent (hand and foot care field)

Application Field: Hand and foot care, nail care

Corresponding Products: Nail softeners, ingrown toenail correction and care products

Applicability Principle: Nails are also composed of keratin. Thioglycolic acid and its salts can soften thickened or deformed nail plates (such as ingrown toenails), facilitating correction and shaping.

5.Depilatory agent for leather processing (core application in the leather industry)

Application Field: Leather industry

Corresponding Products: Raw hide depilatories, pre-tanning depilation processes, fur processing auxiliaries

Applicability Principle: Prior to tanning, hair and hair roots need to be removed from raw hides. Thioglycolates (calcium/sodium salts) can reduce the disulphide bonds of keratin around broken hair follicles, loosening and removing hair roots. It is milder than the traditional lime-sodium sulfide method and produces higher-quality leather, making it a classic depilatory chemical in leather tanning, and one of the main applications of the TGA family in leather processing.

6.Raw materials for PVC heat stabilizer synthesis (plastics industry)

Application Field: Plastics processing and additives industry

Corresponding Products: Organotin mercaptoacetic acid ester PVC heat stabilizers (such as isooctyl mercaptoacetate), processing aids for PVC products

Applicability Principle: Mercaptoacetic acid and its organotin derivatives (general formula \(\boldsymbol{R_2Sn(SCH_2CO_2R')_2}\)) are among the most effective heat stabilizers for PVC. They can capture hydrogen chloride released at high processing temperatures and prevent PVC degradation and discoloration. Calcium mercaptoacetate serves as upstream raw material for synthesising these mercaptoacetic acid salts, supporting manufacturing of PVC pipes, profiles and sheets.

7.Raw materials for manufacturing mercaptoacetate series products (fine chemicals)

Application Field: Fine Chemicals

Corresponding Products: Raw material for the synthesis of sodium thioglycolate, ammonium thioglycolate, thioglycolate esters, and other related salts and esters

Applicability Principle: Calcium salts, sodium salts, ammonium salts and esters are suitable for different scenarios (hair removal, perming, culture media, stabilizers). Calcium thioglycolate is an important member of the thioglycolate family. Through salt formation, esterification and other reactions, it can derive a series of downstream products and acts as one of the basic raw materials in the fine chemical industry chain.

8.Metal ion complexation and detection reagents (analytical detection field)

Application Field: Industrial analysis and testing

Corresponding Products: Iron/Molybdenum/Silver/Tin ion detection reagents, colorimetric complexing reagents, industrial water quality analysis reagents

Applicability Principle: Thioglycolate ions can form characteristic complexes with various metal ions. For example, ferrous ions react with thioglycolate to form a reddish-purple ferric complex. This colour reaction enables qualitative and quantitative detection of metal ions, so it is a classic metal complexing colorimetric reagent for industrial raw material testing and water quality analysis.

9.Industrial rust removers and wheel cleaners (cleaning industry)Application Field: Industrial cleaning, automotive care

Corresponding Products: Fallout remover, industrial rust remover, metal surface treatment agent

Applicability Principle: Thioglycolate can complex and dissolve iron oxide (rust) and remove rust spots on wheel hub surfaces caused by brake dust and road metal debris, restoring wheel hub gloss. It functions as the active complexing agent in industrial rust removers and automotive wheel hub cleaning products.

10.Synthesis of sulphur sources based on nanomaterials (Field of New Materials)

Application Field: Nanomaterials, New Materials

Corresponding Products: Sulphur source for metal sulphide nanostructures (quantum dots, nanocrystals) synthesis, precursors for functional nanomaterials

Applicability Principle: Thioglycolic acid and its salts can act as a sulphur source and stabilising ligand under hydrothermal/solvothermal conditions. It supplies sulphur and controls the nucleation and growth of nanocrystals to prevent their aggregation. It is a multi-purpose reagent in nanomaterial preparation for synthesising metal sulphide nanostructures and quantum dots.

11.Thioglycollate medium (microbiology)

Application Field: Microbiology, laboratory testing

Corresponding Products: Thioglycollate broth, media for anaerobic culture and sterility testing

Applicability Principle: Thioglycolates (such as sodium salts) serve as reducing agents in culture media. They react with dissolved oxygen to maintain low redox potential and create an environment suitable for the growth of anaerobic and microaerophilic bacteria. They are typical components of sterility testing and anaerobic culture media.

12.Protein chemistry research reagents (Biochemistry Field)

Application Field: Biochemistry, Protein science

Corresponding Products: Protein disulphide bond reduction reagents, keratin/hair structure research reagents, protein denaturation research solvent systems

Applicability Principle: Thioglycolate selectively reduces disulphide bonds in proteins without damaging the peptide backbone. It is an important chemical tool for studying the structure of disulphide-rich proteins such as keratin, clarifying protein conformation and function, and acts as an auxiliary reductant in proteomics sample processing.

13.Application Field: Analytical Chemistry

Corresponding Products: Argentometric titration reagents; colorimetric reagents for metal ion determination; pretreatment reagents for thin layer chromatography / gas chromatography standards

Applicability Principle: Thioglycolic acid can be used as a standard reagent in the argentometric method (potentiometric titration with silver nitrate) for the determination of thiol compounds. Its metal complexation colorimetric property is also applied for colorimetric detection of metals such as iron. It also serves as a standard substance for chromatographic determination of thioglycolic acid in hair perming and hair removal products.

To summarise, calcium thioglycolate (CAS 814-71-1) is produced by the reaction of calcium with thioglycolic acid (CAS 68-11-1). It has wide applications in cosmetics (hair removal, perm lotions, hair straighteners), industry (leather depilation, PVC stabiliser synthesis, thioglycolate manufacturing, metal detection, rust removal and cleaning, sulphur sources for nanomaterials) and scientific research (thioglycolate culture medium, protein disulphide bond research, analytical titration and colour development). It works through five core mechanisms: disulphide bond reduction, alkaline softening, calcium salt carrier, oxidative regeneration and metal complexation. Since the 1940s, its primary function of “breaking disulphide bonds and softening keratin” has been utilised. It is one of the most widely used varieties in the thioglycolate family.