Pigment lithopone: what it is, how it works, and a buyer's guide

What is pigment lithopone?

Pigment lithopone is a white inorganic composite pigment made by co-precipitating zinc sulfide (ZnS) and barium sulfate (BaSO₄), classified under the Colour Index as Pigment White 5. It delivers a combination of acceptable hiding power, excellent dispersibility, and significantly lower cost compared with titanium dioxide — making it a practical white pigment filler in mass-market industrial formulations.

Within the broader family of inorganic white pigments, lithopone occupies a distinct middle tier. Basic extenders such as calcium carbonate offer little optical contribution; titanium dioxide (TiO₂) sits at the premium end with unmatched refractive index. Lithopone powder bridges the two — providing genuine whitening and opacity at roughly 30–40% of the cost of TiO₂. That economic argument alone explains why global demand for lithopone continues to hold steady despite the dominance of titanium dioxide in high-specification coatings.

Pigment lithopone is defined as: a zinc-based white pigment in which the active component (ZnS) delivers whiteness and hiding power, while the co-precipitated barium sulfate acts as an internal extender that controls dispersion, gloss, and rheology. The two phases are inseparable — formed simultaneously during the precipitation reaction — which distinguishes lithopone from simple physical blends of ZnS and BaSO₄.

Why do so many formulators still overlook its nuances? The short answer is that not all lithopone grades are equal, and selecting the wrong type for your application is a common and costly mistake. Grades are defined primarily by their ZnS content — B28 contains 28%, B30 contains 30%, and B35 contains 35% — and that single variable drives substantial differences in opacity, cost, and UV stability.

Key physical and chemical properties

Lithopone presents as a fine white-to-off-white powder with a density of approximately 4.2–4.3 g/cm³. Oil absorption typically ranges from 12 to 18 g/100 g, which keeps formulation costs manageable. The refractive index of the ZnS component (~2.37) is meaningfully higher than calcium carbonate (~1.58) but lower than TiO₂ (~2.70), which explains the intermediate hiding power. Brightness (CIE L*) for a well-calcined B30 product routinely exceeds 95, making it a viable paint whitening agent for interior applications.

The calcination step: why it matters

Calcination is not optional — it is the process step that transforms raw co-precipitate into a usable zinc sulfide pigment. Actual testing shows that under-calcined material produces poor gloss and unacceptable yellowing in finished coatings. Well-calcined lithopone L grade products, by contrast, achieve fine particle size uniformity and the dispersibility that formulators depend on. The calcination temperature and duration directly govern crystal structure, and therefore the final optical performance of the permanent white pigment.

How lithopone is manufactured: the co-precipitation process

Lithopone is produced through a well-established aqueous co-precipitation route. The process begins with two primary feedstocks — zinc sulfate solution and barium sulfide solution — which are reacted together under controlled temperature and pH conditions. The resulting precipitate contains both ZnS and BaSO₄ in an intimately mixed, nano-scale composite structure.

The key production steps are:

1. Feedstock preparation: Zinc sulfate (ZnSO₄) is dissolved in water; barium sulfide (BaS) is prepared by reducing barite (BaSO₄) with carbon at high temperature.
2. Co-precipitation reaction: The two solutions are mixed in a reaction vessel. The simultaneous precipitation of ZnS and BaSO₄ forms the composite pigment precursor.
3. Filtration and washing: The precipitate is filtered and washed to remove soluble salts, particularly sodium and sulfate ions that would otherwise cause viscosity problems in downstream formulations.
4. Calcination: Dried material is calcined at 600–800 °C. This step determines final particle size, gloss response, and UV stability. Higher calcination temperatures generally yield larger particles with improved hiding power but reduced tinting strength.
5. Quenching and milling: The calcined clinker is quenched in dilute acid solution, then wet-milled and classified to achieve the target particle size distribution.
6. Surface treatment (optional): Modified grades receive organic or inorganic surface treatment to improve weather resistance and dispersibility in non-aqueous systems.
7. Drying and packaging: Final product is spray- or flash-dried, then packaged — typically in 25 kg HDPE bags or 500 kg jumbo bags for bulk shipment.

For a comprehensive background on the chemistry and historical development of this pigment, the lithopone pigment overview on Wikipedia provides a well-structured starting point. That said, commercial grade specifications vary considerably from the textbook description, which is why working directly with certified suppliers remains essential.

How calcination controls grade designation

The B28/B30/B35 designations correspond directly to the ZnS content achieved through process control — primarily reaction stoichiometry and calcination conditions. B35, with its higher ZnS content, requires tighter process control and more energy input, which is why it commands a price premium. Manufacturers in Gujarat and other Indian production hubs have invested in continuous calcination kilns to improve yield consistency, a factor buyers should verify during supplier audits.

Quality indicators to request from any supplier

When evaluating any lithopone manufacturer, request the following test certificates: ZnS content (%), BaSO₄ content (%), water-soluble matter (max 0.3%), residue on 45 µm sieve (max 0.1%), tinting strength relative to standard (min 95%), and oil absorption value. These parameters, aligned with IS 37:1976 requirements (discussed in Section 4), allow meaningful cross-supplier comparison.

Grade comparison: B28, B30, B35 vs titanium dioxide

Choosing the wrong grade is one of the most common and expensive mistakes in white pigment procurement. The table below provides a direct, data-driven comparison across the three main commercial lithopone grades and rutile TiO₂ — the benchmark coating opacity agent for the Indian market.

"TiO₂'s hiding power is approximately 2 to 3 times that of lithopone, and the two cannot be used as simple drop-in substitutes. Lithopone's economic advantage is most compelling in interior and semi-exposed applications where opacity requirements are moderate and cost sensitivity is high." — Industry consensus among Indian paint technologists, 2026

When to use lithopone instead of TiO₂

The titanium dioxide alternative argument is strongest in three scenarios: interior emulsion paints where film thickness can compensate for lower opacity; rubber compounding where whiteness rather than hiding power is the functional requirement; and PVC or plastic white pigment applications where a combination of lithopone and a small TiO₂ boost delivers the target colour at lowest formulation cost. According to 2026 data, EU regulatory pressure on TiO₂ (under the revised EC 1272/2008 classification) is also nudging European-specification export products toward higher lithopone content — a trend Indian manufacturers supplying global brands should factor into their R&D roadmap.

The yellowing misconception

A persistent industry misconception is that all lithopone yellows outdoors. The reality is more nuanced. Under-calcined or improperly quenched material is the culprit — not the chemistry itself. Well-processed B35 with surface treatment passes 500-hour QUV accelerated weathering with ΔE under 2 in many interior formulations. Of course, for genuinely exposed exterior applications, no grade of lithopone matches rutile TiO₂'s UV durability, and that limitation should be acknowledged honestly.

Pigment lithopone in India: pricing, suppliers, and BIS compliance

India's lithopone market is concentrated primarily in Gujarat and Maharashtra — the two states that together account for the majority of domestic production and import-distribution activity. Gujarat-based manufacturers, clustered around Ahmedabad, Vadodara, and Vapi, supply both domestic consumers and export markets across Southeast Asia and the Middle East.

BIS / IS 37:1976 compliance: what buyers must verify

The Bureau of Indian Standards governs lithopone quality under IS 37:1976 — the Indian Standard specification for lithopone. Buyers specifying material for government contracts, defence supply chains, or export to regulated markets must confirm that suppliers hold a valid BIS licence and can provide product certified against IS 37:1976 parameters. Key IS 37:1976 requirements include: minimum ZnS content per declared grade, maximum water-soluble matter of 0.3%, residue on 45 µm sieve not exceeding 0.1%, and minimum tinting strength of 95 relative to standard. Failure to request IS 37:1976 test certificates at the procurement stage is one of the most common compliance gaps found during supplier audits — and one that competitors' content routinely fails to flag. Always request a fresh certificate dated within 12 months; IS 37:1976 certification is not permanent.

Application guide: paint, rubber, plastics, and paper

Lithopone's versatility is one of its underappreciated strengths. Based on real-world formulation data from Indian processing plants, the following recommendations provide a practical starting point for each major downstream industry.

Paint and coatings: interior emulsion and distemper

In interior emulsion formulations, B30 or B35 lithopone is typically used at 10–20% by weight of total pigment+filler package, replacing an equivalent portion of TiO₂. 

Rubber compounding: recommended filler levels

Lithopone is a well-established rubber compounding filler, particularly in white and light-coloured rubber goods — footwear soles, hoses, conveyor belts, and flooring. B28 grade is the standard choice for rubber, used at 20–50 phr (parts per hundred rubber) depending on the whiteness requirement and compound hardness target. Its low oil absorption limits plasticiser demand, an important economic factor in large-batch rubber mixing. The inert barium sulfate phase also improves compound flow and reduces die swell during extrusion — a practical benefit confirmed in case studies from rubber goods manufacturers in Tamil Nadu and Maharashtra.

Plastics: PVC, PP, and masterbatch

As a plastic white pigment, lithopone performs well in rigid and semi-rigid PVC — window profiles, pipes, sheets — where it is used at 3–8 phr alongside a TiO₂ top-up. The synergistic combination is formulated as a "lithopone-extend" approach: lithopone provides body and base opacity; TiO₂ delivers surface brightness and UV protection. In polypropylene and masterbatch applications, B35 is preferred for its higher ZnS content and finer particle distribution, which minimises streaking during thin-film extrusion. Processing temperatures in PVC applications are manageable — lithopone remains thermally stable up to approximately 500 °C — making it compatible with standard PVC processing conditions.

Paper and board: brightness and filler efficiency

In paper coating and filling, lithopone contributes brightness and opacity at lower loading rates than calcium carbonate. The low abrasivity of lithopone also reduces blade wear in high-speed coating operations — an operational benefit that justifies a modest premium over pure carbonate systems.

Storage, transport, and monsoon-season handling

Moisture is lithopone's primary adversary in storage and transit. This is not a trivial concern in India — the southwest monsoon brings weeks of sustained humidity exceeding 85% RH across coastal and central production zones, and that creates real risk of caking, agglomeration, and ZnS oxidation in improperly stored stock.

Storage best practices

Store lithopone powder in sealed HDPE bags within a dry, covered warehouse. Recommended storage conditions: relative humidity below 65%, temperature below 40 °C, away from direct sunlight. Palletised bags should be elevated at least 15 cm off the floor on wooden or plastic pallets to prevent ground moisture migration. First-in-first-out (FIFO) rotation is essential — shelf life under correct conditions is 12 months from manufacture date, but moisture ingress can degrade quality within weeks during peak monsoon season. In Mumbai and Chennai warehouses, silica gel desiccant packs placed within pallet wrapping have shown measurable benefit in maintaining free-flow powder quality through the June–September monsoon period.

Transport and packaging specifications

For inland transport within India, 25 kg double-lined kraft/PE bags remain standard. Jumbo bags (500 kg FIBC) are cost-effective for large buyers but require covered truck transport during monsoon months — open-top trucks are not acceptable for moisture-sensitive pigment. Rail freight is feasible for Gujarat-to-south India routes but demands hermetically sealed container cars. For import shipments from China, insist on 20-ft dry containers with desiccant panels — independent moisture testing at the port of entry (Mumbai JNPT or Chennai) should be standard practice. Lithopone is not classified as a hazardous material under IMDG/GHS for transport purposes, which simplifies documentation.

How to evaluate and select a lithopone supplier

Selecting a reliable lithopone supplier in India involves more than comparing price lists. Think of it like choosing a long-term ingredient partner rather than a commodity trader — quality consistency, regulatory compliance, and supply reliability matter as much as the lithopone price per kg quoted on day one.

A structured supplier evaluation checklist

The following checklist reflects industry best practice for B2B pigment procurement in the Indian market:

1. BIS licence and IS 37:1976 certification: Request the current BIS licence number and a product-specific IS 37:1976 test report issued within the last 12 months.
2. Technical data sheet (TDS): Verify ZnS content, BaSO₄ content, whiteness (CIE L*), tinting strength, oil absorption, sieve residue, and moisture content. Values must align with the declared grade.
3. Production facility audit or third-party inspection report: For first-time suppliers, request a recent SGS or Bureau Veritas plant audit report. Gujarat-based manufacturers typically maintain these for export customers.
4. Batch-to-batch consistency data: Ask for 6-month QC trend data for ZnS content and tinting strength. Coefficient of variation above 3% on ZnS content is a red flag.
5. Packaging and moisture protection: Confirm double-lined bags, lot number labelling, and manufacture date. Reject any supplier who cannot confirm bag specification.
6. References from existing Indian customers: Request two verifiable references from customers in your own industry segment — paint, rubber, or plastics. This step is frequently skipped and frequently regretted.

Conclusion: making the right lithopone procurement decision

Pigment lithopone remains a commercially relevant and economically compelling white pigment for Indian manufacturers in paint, rubber, plastics, and paper — particularly as input cost pressure intensifies in 2026. The grade you select, the supplier compliance you verify, and the storage discipline you maintain collectively determine whether lithopone delivers its promised value or creates downstream quality problems. B30 represents the best all-round entry point for most applications; step up to B35 where opacity matters; and never compromise on IS 37:1976 certification regardless of the price advantage a non-certified supplier offers.

The competitive advantage in sourcing this material comes not from finding the lowest lithopone price per kg, but from finding a supplier with consistent ZnS content, reliable certification, and the operational capacity to maintain supply through India's challenging monsoon season. That combination is what separates a reliable raw material partner from a one-time transactional vendor — and it is worth the additional diligence during the initial qualification process.

Frequently asked questions

Q: What is pigment lithopone and what is it used for?

A: Pigment lithopone is a white inorganic composite pigment (Pigment White 5) made from co-precipitated zinc sulfide and barium sulfate. It is used as a white pigment filler and coating opacity agent in interior paints, rubber compounding, PVC, plastics, and paper where moderate hiding power and low cost are priorities.

Q: What is the difference between lithopone B28, B30, and B35?

A: The designations refer to zinc sulfide content — 28%, 30%, and 35% respectively. Higher ZnS content means greater hiding power, better tinting strength, and higher cost. B30 is the standard industrial grade for interior paint; B28 is preferred for rubber and paper; B35 suits premium plastic and coating applications requiring maximum whiteness.

Q: Can lithopone replace titanium dioxide completely?

A: No — TiO₂ has 2 to 3 times the hiding power of lithopone and far superior UV stability for outdoor applications. Lithopone works best as a partial TiO₂ replacement in interior formulations or as a standalone white pigment in rubber and paper, where cost efficiency matters more than maximum opacity. A partial substitution of 10–20% TiO₂ by lithopone in interior paint is a well-established and cost-effective strategy.

The pricing information contained herein is based on third-party market research data and is intended solely for reference; it does not constitute a formal price quotation from our company. Actual pricing is subject to our official quotation.