Reactive Black 5 Dye Supplier: The Complete Technical Guide for Textile Buyers
Every season, millions of metres of jet-black cotton fabric move from dye houses in Tiruppur, Dhaka, and Ho Chi Minh City into garments that end up on shelves in Milan, Madrid, and São Paulo. The dye sitting at the centre of most of those supply chains is Reactive Black 5 (Reactive Black B) — a molecule so well-suited to cellulosic fibres that it has remained the dominant commercial black reactive dye for over four decades. Yet buyers who purchase it regularly — traders, buying agents, mill procurement managers — rarely have a complete picture of what they are actually buying. This guide changes that. Whether you are a dye importer in Turkey placing a first container order, a buying agent in Bangladesh specifying dyes for a new garment programme, or a procurement manager in Morocco evaluating suppliers for the season ahead, you will find everything you need here to source confidently from any Reactive Black 5 (Reactive Black B) dye supplier.
Reactive Black 5 (Reactive Black B) is a bifunctional vinyl sulphone reactive dye used primarily to dye cellulosic fibres — cotton, viscose, modal, lyocell — to deep, neutral black shades. It belongs to the azo class of dyes and reacts with the hydroxyl groups in cellulose through a covalent bond, which is why the colour does not simply wash out the way a direct dye or vat dye might under repeated laundering.
The dye was commercialised in the 1970s and quickly became the industry reference for black reactive dyeing. Its dominance comes from a combination of factors: excellent depth of shade, manageable process chemistry, broad compatibility with standard exhaust and continuous dyeing equipment, and a performance profile that satisfies the fastness requirements of most commercial garment programmes.
For buyers, "Reactive Black 5" is not just a colour. It is a specification. When a garment buyer in Europe or the United States places a fabric requirement against a particular black standard — say, a colour approval with a minimum wash fastness of 4 on the ISO scale — Reactive Black 5 (Reactive Black B) is almost always the dye behind it.
CI Number, CAS Number, and Alternate Trade Names
Knowing the correct identifiers protects buyers from substitution and ensures consistent quality across supply chains.
Colour Index (CI) Generic Name: Reactive Black 5
Common Name: Reactive Black B
CI Number: 20505
CAS Number: 17095-24-8
Molecular Formula: C₂₆H₂₁N₅Na₄O₁₉S₆
Molecular Weight: 991.82 g/mol
In trade, the dye appears under numerous commercial names depending on the manufacturer: Remazol Black B (Dystar), Remazol Black GF, Synozol Black B, Everzol Black GF, Livafix Black E-G, and others. Avi Chemicals markets the dye under its own branded grade Colactive Black B. Always cross-reference the CI number and CAS number when evaluating any commercial product — brand names vary widely by country and manufacturer, but the chemistry underneath should be identical.
Chemical Structure and Molecular Profile
Reactive Black 5 (Reactive Black B) contains two vinyl sulphone reactive groups attached through an azo linkage to a naphthalene-based chromophore. The bifunctional nature is the key structural feature that separates it from monofunctional reactive blacks in terms of dye-fibre bond durability.
The molecule carries four sulphonate groups (–SO₃Na), which confer high water solubility and good electrolyte compatibility during the dyeing process. The azo groups (–N=N–) are responsible for the deep black colour through the absorption of visible light across a broad spectrum. The vinyl sulphone groups (–SO₂–CH=CH₂) are the reactive sites that form covalent ether linkages with cellulose hydroxyl groups under alkaline conditions.
In terms of physical form, Reactive Black 5 (Reactive Black B) is supplied as a dark brown to black powder or granule with a dye content typically in the range of 50 to 60 per cent, the remainder being diluting salts and standardising agents. Shade strength — often expressed as a percentage of a reference standard — is the primary specification buyers and dyers use to compare batches and suppliers.
What Makes the Dye-Fibre Bond so Durable?
The answer lies in the covalent bond formed between the vinyl sulphone group and the cellulose hydroxyl group. Unlike ionic or van der Waals bonds (which hold direct dyes in place), a covalent bond requires actual chemical energy to break. In practical terms, this means the colour is part of the fibre, not just sitting inside it.
The bifunctionality matters because each dye molecule can theoretically bond at two separate sites on the cellulose chain. Higher fibre fixation — typically in the range of 60 to 75 per cent under well-controlled process conditions — means less hydrolysed dye in the effluent, less wash-off time required, and better build-up at heavy depths of shade. This is particularly relevant for buyers specifying deep black on denim, heavy jersey, and woven shirting.
Key Performance Characteristics of Reactive Black 5
Buyers need to understand fastness properties not as abstract laboratory scores but as commercial guarantees. When a fast fashion buyer in Dhaka commits to a 20,000-piece run on black jersey, or when a home textiles importer in Istanbul approves a black fabric swatch, the fastness data underneath that approval is almost always based on Reactive Black 5 performance benchmarks.
The following ratings are typical for well-processed Reactive Black 5 on mercerised cotton — actual results depend on dyeing conditions, after-treatment quality, and the specific commercial grade used.
Fastness Property | Test Standard | Typical Rating |
Wash Fastness (colour change) | ISO 105-C06 | 4–5 |
Wash Fastness (staining on cotton) | ISO 105-C06 | 4–5 |
Dry Rubbing Fastness | ISO 105-X12 | 4–5 |
Wet Rubbing Fastness | ISO 105-X12 | 3–4 |
Light Fastness | ISO 105-B02 | 3–4 |
Perspiration Fastness (acid/alkaline) | ISO 105-E04 | 4–5 |
Wash Fastness, Light Fastness, and Rubbing Fastness — What the Numbers Mean for Buyers
Wash Fastness (4–5): On a scale of 1 to 5, a rating of 4 to 5 means the colour shows negligible change after repeated laundering at the specified temperature. For buyers in the EU market, EN ISO 105-C06 at 40°C is the most common commercial requirement. Reactive Black 5 routinely meets this threshold when dyed and after-treated correctly.
Light Fastness (3–4): This is where buyers sometimes misread the specification. A light fastness of 3 to 4 is adequate for most indoor apparel and home textiles but may fall short for outdoor performance fabrics, awnings, or technical textiles that require ratings of 5 or above. If your end-use is outdoor or high-UV exposure, discuss this explicitly with your supplier.
Wet Rubbing Fastness (3–4): Wet rubbing fastness is the most demanding test and the one most likely to trigger complaints at garment inspection. A rating of 3 is commercially acceptable for most markets, but buyers sourcing for European fast fashion retailers should confirm their specific requirements, as some brands now specify a minimum of 3–4. Achieving the higher end consistently requires correct soaping-off procedures and an appropriate fixing treatment after dyeing.
Perspiration Fastness (4–5): This is particularly relevant for buyers specifying T-shirts, underwear, and activewear. Reactive Black 5 performs strongly here, which is one reason it dominates the cotton knitwear segment.
How to Dye Cotton and Viscose with Reactive Black 5 — Step-by-Step Application
Process knowledge matters for buyers because it gives you the ability to troubleshoot with your dye house, write better technical specifications, and evaluate supplier claims. You do not need to be a dye house chemist to understand the basics.
Exhaust Dyeing Method
Exhaust dyeing is the standard approach for yarn, loose fibre, knit fabric in rope or open-width form, and woven fabric on jet or overflow machines. The dye is absorbed from a circulating liquor onto the substrate over time.
Typical Process Parameters for Deep Black (6–8% owf) on Mercerised Cotton Jersey:
Preparation: Ensure fabric is well-scoured, bleached if required, and free of residual peroxide. Reactive dyeing is sensitive to preparation quality — uneven preparation produces unlevel dyeing.
Loading and initial temperature: Load fabric at 30–40°C. Dissolve the required quantity of Reactive Black 5 in hot water (60–70°C) and filter before adding to the bath.
Salt addition: Sodium sulphate or sodium chloride, typically 60–100 g/L for heavy depths of shade, is added in stages to promote dye migration onto the fibre. The electrolyte drives the anionic dye molecule toward the negatively charged cellulose surface.
Alkali addition: Soda ash (sodium carbonate, 20–25 g/L) or sodium hydroxide (caustic soda, 3–5 g/L) is added in stages at 60°C to activate the vinyl sulphone reactive group and initiate the covalent bonding reaction.
Dwell time: Hold at 60°C for 45–60 minutes after alkali addition to achieve maximum fixation. Do not short this step — inadequate fixation is the most common cause of poor wash fastness complaints.
Washing-off: Drain, cold rinse, hot rinse (70–80°C), soap at boil (2 g/L non-ionic detergent, 95°C, 15 minutes), hot rinse, cold rinse. The soaping-off step is critical for removing hydrolysed dye, which is unfixed and will stain if left on the fabric.
Fixing treatment (optional but recommended): A cationic fixing agent applied after soaping can improve wet rubbing fastness by 0.5 to 1 grade, which matters when specifying for European retailers.
Liquor ratio: Typically 1:6 to 1:12 depending on machine type. Lower liquor ratios improve dye exhaustion and reduce effluent volume but require more accurate dosing.
Continuous / Pad-Batch Method
The pad-batch method is preferred for large-volume open-width woven and knit fabric. It uses less water, produces more consistent levelness on large batches, and is more economical on energy per metre of fabric processed.
Process outline:
Padding: Fabric passes through a padder trough containing the dye solution (typically 20–50 g/L Reactive Black 5 depending on required depth) plus sodium hydroxide (5–8°C Baumé concentration) at ambient temperature. Wet pick-up is controlled to 65–75 per cent.
Batching: Padded fabric is batched on a roll wrapped in polyethylene film to prevent drying and stored at ambient temperature (ideally 20–25°C) for 6–24 hours. Fixation occurs during this dwell period via cold pad-batch chemistry.
Washing-off: The batched roll is washed on a continuous washing range: cold rinse → hot rinse (70°C) → boil soap → hot rinse → cold rinse → dry. The soaping step is essential and must not be shortened.
Key advantage over exhaust: Pad-batch does not require salt, significantly reducing the total dissolved solids (TDS) load in effluent — a growing consideration for mills operating under tightening environmental regulations in Bangladesh, Vietnam, and India.
Industries and End-Uses: Where Reactive Black 5 Shows Up
Understanding where Reactive Black 5 (Reactive Black B) is used commercially helps buyers anticipate demand, plan inventory, and recognise which end-use sectors are growing or contracting.
Apparel and Fashion
The apparel sector accounts for the majority of global Reactive Black 5 (Reactive Black B) consumption. Black is the single most ordered colour in most garment programmes worldwide, and it is near-universal in seasonal collections across fast fashion, value, and premium segments. Key sub-sectors include:
Cotton T-shirts and knitwear — the highest-volume application globally. Tiruppur alone produces hundreds of millions of garments per year, and black jersey is consistently one of the top three colours across buyers from Europe, the United States, and Australia.
Denim — both woven denim fabric dyed with Reactive Black 5 directly and overdyed indigo denim. Ahmedabad and Surat are significant centres for black denim production in India.
Casual and workwear shirting — woven cotton poplin, twill, and oxford weaves dyed for uniform and casualwear programmes. Buyers in Spain and Italy frequently specify black viscose blends for fashion shirting where drape and colour depth are priorities.
Activewear and athleisure on cotton and viscose — growing rapidly across all markets. The combination of Reactive Black 5's depth of shade and adequate perspiration fastness makes it suitable for the cotton-modal blends increasingly popular in this segment.
Home Textiles, Industrial Fabrics, and Beyond
Bed linen and towelling — black is a perennial hotel and spa specification. Buyers in Turkey (a major home textiles exporter) and Pakistan source significant quantities of reactive black dyes for this sector.
Upholstery and furnishing fabrics — plain-dyed cotton and viscose furnishing fabrics. Light fastness requirements here are more demanding; buyers should specify light fastness grade requirements explicitly with their supplier rather than relying on standard apparel-grade performance.
Sock and hosiery — a large-volume application in Bangladesh and Turkey. The small lot sizes and frequent shade matching required in this sector mean that consistency between dye lots is a critical purchase criterion.
Nonwovens and technical textiles — specialist applications where coloured cellulosic nonwovens are required. Growth segment, though volumes remain small relative to mainstream apparel.
Not all black reactive dyes are interchangeable. Buyers who switch supplier without checking dye chemistry compatibility risk unlevel re-dyeing, fastness failures, or incompatibility with existing dye-house recipes.
Reactive Black 5 vs. Reactive Black 8 (CI Reactive Black 8): Reactive Black 8 is a monofunctional vinyl sulphone dye with slightly different application temperature requirements and generally lower wash fastness in deep shades. It is sometimes offered as a lower-cost alternative. For buyers holding fastness specifications of 4–5 wash fastness on dark shades, the substitution risk is real.
Reactive Black 5 vs. Reactive Black B-133%: This is not a different dye but a higher-strength (133 per cent) commercial version of Reactive Black 5 (Colactive Black B). Higher strength means less product is required to achieve the same depth of shade — relevant for buyers comparing price on a cost-per-kilo basis. Always compare on a cost-per-dyed-kilogram-of-fabric basis, not raw product cost.
Reactive Black 5 vs. Cold Brand Black (low-temperature dyeing grades): Some suppliers offer modified Reactive Black 5 (Colactive Black B) grades optimised for lower fixation temperatures (around 40°C rather than 60°C). These can reduce energy costs in pad-batch processing. Confirm with your dye house before specifying.
Common buyer mistake: Purchasing on price alone without confirming dye content/shade strength. A 55 per cent dye content product priced 15 per cent below a 60 per cent product may actually cost more per depth unit of shade achieved. Always request dye content and shade strength documentation.
How to Evaluate a Reactive Black 5 Dye Supplier: A Buyer's Checklist
Sourcing dye from a new supplier — especially across international markets — involves more than price negotiation. Here is a practical evaluation framework for importers, agents, and procurement managers.
1. Technical documentation package Request and review: Certificate of Analysis (CoA) per lot, Material Safety Data Sheet (MSDS/SDS), shade strength report against a reference standard, and dyeing application note or Technical Data Sheet (TDS). A credible supplier provides all four without being asked twice.
2. Shade strength consistency Ask for the CoA from the last five to ten production batches and check the shade strength variance. Acceptable commercial variance is typically ±3 to 5 per cent. Wider variance will cause metamerism problems between lots.
3. Impurity profile and restricted substances For buyers supplying EU, UK, US, or Japanese markets, the dye must be free from restricted aromatic amines under REACH (EU Regulation 1907/2006), OEKO-TEX Standard 100, and equivalent frameworks. Request confirmation that the dye complies with the relevant restricted substance list for your target market.
4. Packing and handling specifications Confirm packing options (25 kg fibre drums, 25 kg paper bags, 500 kg bulk bags), packaging integrity, and moisture barrier protection. Reactive Black 5 is hygroscopic; improper packing leads to caking and uneven dissolution.
5. Minimum order quantity (MOQ) and lead time Standard commercial MOQ ranges from 100 kg to 500 kg for trial orders. Confirm production lead time, typical dispatch time from India, and port of loading (most Ahmedabad-based manufacturers ship from Nhava Sheva/JNPT or Mundra).
6. Quality assurance systems Does the supplier maintain in-house QC lab capability including spectrophotometric shade measurement? Can they provide dye-on-fabric confirmation samples before shipment? An in-house lab is a significant differentiator for buyers who cannot afford to receive off-standard product at destination.
Direct manufacturing means consistent pricing and supply security. You are not subject to the mark-up and availability risk that comes with buying through intermediaries. When feedstock costs shift — as they have done repeatedly since 2020 — a manufacturer can absorb or negotiate those shifts in a way that a trader cannot.
Export experience across more than ten countries. Avi Chemicals ships Reactive Black 5 (Reactive Black B) and the broader reactive, acid, and direct dye range to textile markets across Asia, the Middle East, Africa, Europe, and the Americas. Logistics, documentation (commercial invoice, packing list, CoA, MSDS), and customs compliance are routine, not exceptional.
In-house quality control laboratory. Every production lot is spectrophotometrically tested against a reference standard before release. Dye content, shade strength, and solubility are checked per batch. Buyers receive lot-specific CoA as a standard export document.
Technical support. The Avi Chemicals team can advise on process parameters, recipe adjustments, and shade matching for specific end-use requirements. For buyers who are evaluating Reactive Black 5 for the first time or switching from a current supplier, application-level technical guidance reduces trial and error time in the dye house.
FAQ: Reactive Black 5 — Common Questions from Textile Buyers
Q: What is the minimum order quantity for Reactive Black 5 from Avi Chemicals?
A: For export orders, the standard trial quantity is 100 kg, typically supplied in 25 kgs boxes. Repeat commercial orders generally start from 500 kg upward. Contact Avi Chemicals directly for your specific requirement — MOQ can be discussed based on shipping feasibility and destination port.
Q: Does Reactive Black 5 comply with REACH and OEKO-TEX?
A: Reactive Black 5 (Reactive Black B) from a reputable manufacturer does not contain restricted aromatic amines and is suitable for use in OEKO-TEX Standard 100 certified production, provided correct dyeing and washing-off procedures are followed. Avi Chemicals can supply MSDS documentation confirming compliance for your market. Note that REACH SDS (Safety Data Sheet) in the EU-specific format is a separate document from a standard MSDS — discuss your specific documentation requirements when placing an inquiry.
Q: What is the shelf life of Reactive Black 5 (Reactive Black B)?
A: Under correct storage conditions — cool, dry, away from direct sunlight, in sealed original packaging — Reactive Black 5 (Reactive Black B) has a practical shelf life of 18 to 24 months. High humidity accelerates hydrolysis of the reactive group, reducing fixation efficiency. Do not store in coastal or high-humidity environments without climate-controlled warehousing.
Q: Can Reactive Black 5 be used on polyester-cotton blends?
A: Reactive Black 5 (Reactive Black B) dyes the cotton component only. For PC blends, a separate disperse dye is required for the polyester component, applied in a separate dyeing stage or in a one-bath two-stage process. The reactive and disperse components are not applied simultaneously in standard commercial practice. Discuss blend ratio and target shade depth with your dye house to determine the correct combination.
Q: How should I compare prices from different Reactive Black 5 suppliers?
A: Always compare on a shade-strength-adjusted basis. A product at USD X per kg with 55% dye content and a product at USD Y per kg with 60% dye content are not directly comparable on raw price. Calculate the effective cost per depth unit of shade by dividing the price by the shade strength percentage. Also factor in batch-to-batch consistency variance, documentation quality, and after-sales technical support — these have a real cost when things go wrong at the dye house.
Q: What shipping terms does Avi Chemicals offer for export orders?
A: Export orders are typically quoted on FOB Nhava Sheva (JNPT) or FOB Mundra terms. CIF quotations for major destinations can be arranged on request. Standard lead time from order confirmation to cargo readiness is 7 to 14 working days for regular grades. Contact the export team for specific quotation requirements.
Q: I am a buying agent in Bangladesh specifying dyes for a garment factory. Can I approach Avi Chemicals directly?
A: Yes. Avi Chemicals works with dye importers, buying agents, and trading houses as well as directly with large-volume end users. If you are specifying dyes on behalf of manufacturers and would like to establish a technical reference and commercial relationship, reach out through the enquiry form on avichemicals.com or contact the export team directly.
Ready to source Reactive Black 5 (Reactive Black 5) for your next season's programme? Contact Avi Chemicals to request a product sample, technical data sheet, and commercial quotation. Our export team responds to all international enquiries within one business day.
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