Dyeing Cotton Black with Logwood

One of our dyeing projects this week has been working on a really good, consistent recipe for dyeing cotton black. Black was, historically, one of the most difficult colors to produce using natural dyes. One route to black is to dye something to a really dark midnight blue in an indigo vat, then overdye it with saddened yellow and red (weld and madder are the most likely candidates) to approximate black. However, the most direct route is logwood + iron, since iron will “sadden” logwood to a gray or near-black. This combination is still used today to dye silk medical sutures black, since it is considered safer on a wound than a synthetic black color. However, getting a really deep black on cotton is much harder than on wool and silk.

We’ve been experimenting with recipes from two older dyeing manuals, Hummel’s 1885 “The Dyeing of Textile Fabrics” (pp. 319-322) and Knecht’s 1917 “A Manual of Dyeing.” (pp. 334-340). They are very helpful on many points, but frustratingly vague on others. For example, they advise “passing through” a weak lime-water bath before mordanting the cotton with iron. But for how long? At what temperature? What PH should the lime bath be? We’ve been experimenting with different variables this week and are pretty happy with the results. The next step is to standardize the recipe based on what worked best, then we’ll dye a full cotton scarf to make sure the recipe works consistently. Afterwards, we’ll post the full recipe on our Guide to Dyeing with Logwood and Guide to Dyeing with Royal Logwood Extract so other dyers can reproduce the same shade with a minimum of fuss.