Frequently Asked Questions
Q: Which dye type is best for 100% cotton knitted garments?
A: Reactive dyes are the standard choice for 100% cotton — they form a chemical bond directly with the cellulose fibre, giving excellent wash fastness (4–4.5 rating) and a wide, vibrant colour range. For applications requiring the highest possible fastness (hospitality linen, workwear, outdoor textiles), vat dyes are superior but significantly more expensive to process.
Q: Can disperse dyes be used on cotton?
A: Disperse dyes are designed for synthetic fibres (polyester, nylon, acetate) and do not bond with cotton. If used on cotton without special finishing, the dye will wash out almost entirely. For cotton-polyester blends, a two-step dyeing process is used — reactive for the cotton portion, disperse for the polyester — requiring precise bath management to avoid cross-staining.
Q: Why do some black garments turn brown or greenish after repeated washing?
A: This usually indicates either a poor-quality reactive black dye that wasn’t properly fixed, or the wrong dye type chosen for the fibre. A true deep black on cotton requires a combination of reactive dyes (often red, blue, and yellow reactive blacks) carefully balanced. Single-component “cheap black” formulations shift colour as the weaker dye component fades first. Quality dyehouses use multi-component formulations for black and test wash fastness before bulk production.
Q: How does dye selection affect the final price of my garment?
A: Reactive dyes for cotton add approximately 3–8% to fabric cost compared to undyed greige. Vat dyes are 15–30% more expensive than reactive. The dyeing process (energy, water, chemicals, time) is often a larger cost factor than the dye itself. Requesting test certificates and high-fastness specifications will increase cost slightly but significantly reduces claims, returns, and customer complaints down the line.
Q: What should I look for in a dye certificate to verify quality?
A: A valid dye certificate should state the test standard used (e.g. ISO 105-C06 for wash fastness), the test result as a numerical grade (e.g. 4.0), the shade/colour tested, the lab that conducted the test, and the date. Be cautious of vague certificates that say “meets standard” without a specific grade number — ask for the actual test report.
Q: Does the choice of dye affect OEKO-TEX certification eligibility?
A: Yes significantly. OEKO-TEX Standard 100 maintains a list of prohibited substances including certain reactive dyes, disperse dyes, and dye intermediates. To achieve OEKO-TEX certification, only approved dye formulations may be used. Your dyehouse must test the finished fabric, not just confirm the dye type. Al Madni coordinates OEKO-TEX compliance through M.R. Garment Industries for orders requiring certification.