For Reactive Black 5 and Reactive Red 195, specify the dye by its Colour Index name, its strength against an agreed standard, its shade tolerance, solubility, physical form and the fastness it must reach on your fabric. A purity percentage alone does not describe a reactive dye.
Both are high-volume reactive dyes for dyeing cotton and other cellulosic fibres. Reactive Black 5 is a vinyl sulphone type, while Reactive Red 195 is a bifunctional dye with two different reactive groups. Because the makers' versions differ, the specification is what keeps your dyehouse results repeatable.
Identify the product exactly
Start with the Colour Index generic name, such as C.I. Reactive Black 5 or C.I. Reactive Red 195, and add the CAS number from the supplier's SDS. Many sellers offer different commercial products under the same name, so the C.I. name is a starting point, not a full description.
Our guide on the Colour Index and C.I. numbers explains what the name does and does not tell you.
The points to put in the specification
Write each of these as a measurable requirement, with the test method and tolerance:
- Strength: relative colour strength against a named standard sample, measured by spectrophotometer under set dyeing conditions. See dye strength and how it is measured.
- Shade: a tolerance on colour difference to the standard, stated as a DE value and the method used. See shade matching tolerance.
- Physical form: powder, granule or liquid, with dust level for powders and a stable concentration for liquids.
- Solubility: how much dissolves in water at the dyeing temperature, with no residue on a filter test.
- Moisture and inorganic salt content, because they change the real dye content of the lot.
- Fastness to washing, light and rubbing on your fabric, at the depth you dye.
Why black and red behave differently
Blacks are usually deep shades, so a small strength difference changes how much dye each kilo of fabric needs. Ask the supplier for fastness at the depth you use, not only at a pale shade. Reds are less forgiving of shade drift, because buyers see a small change in hue easily.
With either dye, run a laboratory dyeing against your standard before you approve a lot, and again on each shipment. Our guide on batch consistency in dyes shows how to set up the comparison.
Compliance and paperwork
If your customers follow restricted-substance lists, ask for test evidence against them. Read banned amines and dye testing and ZDHC MRSL and Indian dyes. Ask the supplier for the TDS, the SDS and a certificate of analysis for each batch.
Check that each document names the same product, the same lot and the same manufacturer. Details are in what to put in a reactive dye specification, which this article builds on.
Next step
Once the specification is written, send it to several plants and compare the results of laboratory dyeings, not only the paper. We find and audit dye makers, check samples and documents, and have lots tested. To compare suppliers for these dyes, book a free sourcing review.