What textile and detergent grade salt is

Textile and detergent grade salt is sodium chloride selected or refined for low calcium and magnesium (hardness), low iron and low insolubles, supplied at a consistent particle size that dissolves quickly and cleanly. It can be washed and refined solar salt or vacuum salt. What separates it from ordinary industrial salt is not a higher NaCl percentage on the certificate. It is the impurities that the salt brings into the process, because in a dye bath or a detergent batch, salt is used at concentrations high enough for small impurity percentages to matter.

Raw solar salt contains insoluble dirt and clay, soluble calcium and magnesium salts and typically 4–6% moisture. Washing removes much of the surface load; refining and vacuum crystallisation remove more. India produces all three grades, most of them in Gujarat, which made about 85% of India’s salt in 2021-22, according to the Indian Bureau of Mines.

You soften your water — then the salt puts the hardness back

This is the most important section of this page.

Dye houses invest in softening their process water, because calcium and magnesium can form insoluble precipitates with dyestuffs and soaps. Then they add salt at tens of grams per litre. A comparative study of reactive dyeing published by Textile Learner measured what that salt does to the bath:

Salt in reactive dyeing

Cotton carries a negative surface charge in water, which repels anionic reactive dyes. Salt supplies sodium ions that neutralise that charge and let the dye approach and exhaust onto the fibre. The effect depends on concentration in the bath (grams per litre), not on the weight of fabric. Dyers typically allow 30–45 minutes for salt and dye to distribute evenly before fixation.

Common salt, vacuum salt or Glauber’s salt?

We supply sodium chloride, so it would be convenient to tell you Glauber’s salt is unnecessary. It is not. Here is the honest comparison:

The mass column is arithmetic on molecular weights (NaCl 58.4; Na₂SO₄ 142.0; Na₂SO₄·10H₂O 322.2, each per sodium ion). It is not a dyeing equivalence, which depends on the dye and the recipe.

The practical conclusion: for many mills the best value is not the cheapest common salt and not necessarily Glauber’s salt, but low-hardness refined or vacuum salt, bought against a hardness-at-dosing specification. That is the product we recommend first to dye houses.

Salt in detergents and soap

Liquid detergents, dishwash liquids and shampoos

In formulations built on anionic surfactants such as SLES, sodium chloride is the standard thickener. Salt causes the surfactant heads to pack more closely, building a denser micelle network. In a laboratory series published by Rheology Lab on a base of 26% SLES and 6% cocamidopropyl betaine, adding 0.2% to 2% sodium chloride raised viscosity by about two orders of magnitude. Past a peak, more salt lowers viscosity again — the “salt curve” — so formulators dose salt to a target, and an impure or inconsistent salt moves the target. For clear products, insolubles show as sediment and iron as discolouration.

Detergent powders

In spray-dried and dry-mixed powders, salt is used in some formulations and markets as a lower-cost bulk component, alongside or instead of sodium sulphate. Here moisture and particle size matter as much as purity, because they decide flowability and caking in the pack.

Soap making

In kettle soap making, brine is used to “salt out” soap from glycerine and excess lye. Hardness here reacts with soap to form insoluble calcium and magnesium soaps — the same chemistry as scum in hard water — so the same low-hardness requirement applies.

Specification: what should be in the contract

Where the buyers are

Trade statistics for salt (HS 2501) do not separate textile and detergent grades from other salt, so no one can give you a precise market share for these grades and we will not invent one. What the data do show is where India already ships salt: in 2023, by value, Vietnam (5.01%), Indonesia (5.05%) and Bangladesh (4.82%) were among India’s main salt markets, according to UN Comtrade data reported by TrendEconomy. All three have large cotton dyeing industries. The Gulf, Egypt and North Africa have significant detergent and textile finishing capacity on short sea routes from Gujarat. That is why this guide is published in English, Vietnamese, Indonesian, Arabic and French.

Packing: private labelling from 1 kg to 50 kg, and bulk shipments

RNG Agro Exports offers private labelling from 1 kg to 50 kg pack sizes, and we also handle bulk shipments. Salt is hygroscopic, and dye houses and detergent plants are often humid, so packaging is part of the specification.

Working with RNG Agro Exports

We are based in Rajkot, in the state that makes about 85% of India’s salt, and we supply refined and vacuum salt from qualified producers in Gujarat. For textile and detergent buyers, our approach is simple: we will tell you the hardness our salt adds at your dosing rate before you buy, we will send a pre-shipment sample you can test in your own lab, and we will hold each lot to the hardness and iron limits we agreed. If your shades need Glauber’s salt, we will say so.

Frequently asked questions

What makes salt “textile grade”?

Low hardness, low iron, low insolubles and consistent dissolution, more than a high NaCl figure. In reactive dyeing, salt is added at tens of grams per litre, so impurities that look small on a certificate become significant in the bath. Calcium and magnesium can form insoluble precipitates with dyes and soaps, contributing to spots and uneven shades; iron and insolubles are associated with dull shades and specks. In a comparative study published by Textile Learner, common salt added about 275, 445 and 520 ppm of hardness as CaCO3 at 40, 50 and 60 g/L, while vacuum salt added 165, 235 and 240 ppm. The best way to specify textile salt is to state separate calcium, magnesium and iron limits and the hardness the salt adds at your own dosing rate.

Should a dye house use common salt, vacuum salt or Glauber’s salt?

It depends on the shades and on what the mill controls elsewhere. Glauber’s salt (sodium sulphate) added almost no hardness in the Textile Learner study and is favoured for brilliant and sensitive shades, but per sodium ion supplied, anhydrous sodium sulphate weighs about 1.2 times as much as sodium chloride and the decahydrate about 2.8 times, by simple molecular-weight arithmetic. Common salt is cheapest but brings the most hardness. Vacuum salt roughly halved the hardness of common salt in that study while keeping sodium chloride’s economics. For many mills, low-hardness refined or vacuum salt bought against a hardness-at-dosing specification is the best value; where shade reproducibility is critical, Glauber’s salt may still be the right answer.

How much salt is used in reactive dyeing?

It varies with shade depth, dye and recipe. Pale shades on cotton and viscose may use about 10–15 g/L, and deeper shades considerably more, with comparisons commonly run at 40–60 g/L. Salt works by neutralising the negative surface charge of cotton so that anionic reactive dyes can exhaust onto the fibre, and the effect depends on concentration in the bath rather than on fabric weight. More is not always better: a study in Agriculture and Natural Resources found that higher salt concentrations increased dye aggregation and that visual colour yield fell significantly at 300 g/L. Follow the dye maker’s recipe and control the hardness the salt brings with it.

Why is salt used in liquid detergents?

As a thickener. In formulations based on anionic surfactants such as SLES, sodium chloride makes surfactant molecules pack more closely and builds a denser micelle network, which raises viscosity. In a laboratory series published by Rheology Lab on a base of 26% SLES and 6% cocamidopropyl betaine, adding 0.2% to 2% sodium chloride raised viscosity by about two orders of magnitude. Beyond a peak, further salt lowers viscosity again, which is known as the salt curve. Because formulators dose salt to hit a viscosity target, an inconsistent salt moves the target from batch to batch, and in clear products insolubles appear as sediment and iron as discolouration. Detergent-grade salt should therefore be specified for consistency, insolubles and iron.

Do you offer private labelling and bulk shipments for textile and detergent salt?

Yes. RNG Agro Exports offers private labelling from 1 kg to 50 kg pack sizes and also handles bulk shipments. Packs of 1 kg to 5 kg suit laboratory dyeing, craft dyers and distributors; 10 kg to 25 kg bags suit small and medium mills and detergent formulators; 50 kg woven polypropylene bags with liners suit large mills and detergent plants; jumbo bags of about one tonne suit mills with discharge stations; and loose bulk in containers is quoted on enquiry for large users. Because salt is hygroscopic and dye houses are humid, we treat packaging as part of the specification. Tell us your end use, dosing rate, hardness limit and destination, and we will propose the grade and pack together.

• Low hardness, low iron, low insolubles and consistent dissolution, more than a high NaCl figure. In reactive dyeing, salt is added at tens of grams per litre, so impurities that look small on a certificate become significant in the bath. Calcium and magnesium can form insoluble precipitates with dyes and soaps, contributing to spots and uneven shades; iron and insolubles are associated with dull shades and specks. In a comparative study published by Textile Learner, common salt added about 275, 445 and 520 ppm of hardness as CaCO3 at 40, 50 and 60 g/L, while vacuum salt added 165, 235 and 240 ppm. The best way to specify textile salt is to state separate calcium, magnesium and iron limits and the hardness the salt adds at your own dosing rate.
• It depends on the shades and on what the mill controls elsewhere. Glauber’s salt (sodium sulphate) added almost no hardness in the Textile Learner study and is favoured for brilliant and sensitive shades, but per sodium ion supplied, anhydrous sodium sulphate weighs about 1.2 times as much as sodium chloride and the decahydrate about 2.8 times, by simple molecular-weight arithmetic. Common salt is cheapest but brings the most hardness. Vacuum salt roughly halved the hardness of common salt in that study while keeping sodium chloride’s economics. For many mills, low-hardness refined or vacuum salt bought against a hardness-at-dosing specification is the best value; where shade reproducibility is critical, Glauber’s salt may still be the right answer.
• It varies with shade depth, dye and recipe. Pale shades on cotton and viscose may use about 10–15 g/L, and deeper shades considerably more, with comparisons commonly run at 40–60 g/L. Salt works by neutralising the negative surface charge of cotton so that anionic reactive dyes can exhaust onto the fibre, and the effect depends on concentration in the bath rather than on fabric weight. More is not always better: a study in Agriculture and Natural Resources found that higher salt concentrations increased dye aggregation and that visual colour yield fell significantly at 300 g/L. Follow the dye maker’s recipe and control the hardness the salt brings with it.
• As a thickener. In formulations based on anionic surfactants such as SLES, sodium chloride makes surfactant molecules pack more closely and builds a denser micelle network, which raises viscosity. In a laboratory series published by Rheology Lab on a base of 26% SLES and 6% cocamidopropyl betaine, adding 0.2% to 2% sodium chloride raised viscosity by about two orders of magnitude. Beyond a peak, further salt lowers viscosity again, which is known as the salt curve. Because formulators dose salt to hit a viscosity target, an inconsistent salt moves the target from batch to batch, and in clear products insolubles appear as sediment and iron as discolouration. Detergent-grade salt should therefore be specified for consistency, insolubles and iron.

What this means. At 60 g/L, the common salt in that study added about 520 ppm of hardness to the bath — far more than any softened process water specification. Vacuum salt roughly halved it. In other words, a mill that pays to soften its water and then buys the cheapest salt has put the hardness back into the dyebath through a different door. Read the study for what it is: a single comparison at one shade without statistics, and one test at 50 g/L rated a fail while 60 g/L did not, which tells you that consistency between lots matters as much as the average. But the direction is unambiguous, and it gives you the right question to ask any salt supplier: how much hardness does your salt add at my dosing rate? That is a number you can test in a beaker before you buy a container.