FEEDBACK FRIDAY: This Week in Natural Dye Questions

This week: Storing mordanted wool and getting logwood’s rich purple to stay.

Each week, we are emailed with questions from our natural dye community asking simple and complex questions that we thought might be worth sharing. Here are a handful from this week answered by natural dyer in chief, Kathy Hattori, Founder of Botanical Colors:

How long can wool yarn mordanted with alum & cream of tartar be stored? I have ‘rediscovered’ some handspun that I mordanted over 3 years ago and then stored dry in a sealed container. Does the mordant stay with the yarn or should it be re-mordanted (with the same mordants) before using it? I want to use it to dye with cochineal.

Usually the mordant is still usable on wool, even after several years. You can try a test skein and see how the color reacts. Re-wet the skein first and then immerse it in the cochineal bath. If you like the results, then you can dye the rest of your yarn. If it seems pale, then you can try re-mordanting your yarn.

How do you get Logwood color to stay? I get beautiful deep and bright purples with alum mordant on wool, but all are grey within a few days of being in daylight.

Logwood is considered one of the least lightfast dyes. My experience is that logwood fades if I use very low percentages of alum, or if my fiber is not super clean. If you are diligent about scouring, and I mean scouring, not just washing wool, and also mordant with aluminum potassium sulfate, it is possible to get more lasting results. It’s also important to process the wool for the minimum recommendation of 45 minutes after the dye bath comes to temperature, and it’s possible that longer processing may help prevent fading. Finally, the addition of a small amount of iron to logwood will help with lightfastness but the purple shade will be much darker and nearly black in appearance.