The protein fibers in the fabric took much more color than expected, especially given that lac is not known to be a direct/substantive dye (i.e., a dye that does not require a mordant for protein fibers). The specks of white are the hemp fibers, which took no color as expected. However, the silk yarns turned dusty pink and the wool fibers maroon, and the color faded only somewhat after rinsing and washing. We anticipate that the dye will fade much faster when washed and exposed to ultraviolet light than if it’d been mordanted.

The principal method for mordanting wool requires simmering the fibers in a solution of alum and cream of tartar, an acid salt that protects the wool fibers and increases uniformity of mordant absorption. Wool may be mordanted without the use of cream of tartar, but those methods take much longer, between one to four days.

Again, the hemp fibers did not take any dye, an expected outcome as cream of tartar’s acidity will prevent the alum from attaching to cellulose fibers. And while alum is generally not used by itself to mordant cellulose fibers, it will still increase dye uptake on cellulose fibers (as seen in Method 4 – Silk).

On this swatch, the wool and silk fibers are considerably saturated and burgundy in color. The silk, however, remains lighter than the wool since the acidity from the cream of tartar slows the absorption of the mordant on silk fibers. Also problematic for silk is the heated dye bath, which may damage the fibers.   

Mordanting cellulose requires an additional step, which you can learn more about on our Info & Process page. For this method and the following two, we explored three varieties of aluminum acetate, our preferred mordant for cellulose fibers. One way to create aluminum acetate is by creating a solution of alum and sodium acetate. This creates aluminum acetate at 8% WOF, as well as by-products of sodium sulfate and potassium sulfate.

The results here are rather surprising. The hemp fibers and silk fibers seem to dye the same hue and saturation. Generally, silk can be mordanted the same way as cellulose fibers, so perhaps unsurprising that the two fibers similarly dyed. The wool took some dye as well, but much less saturated than in any of the above methods.

One explanation may be that the by-products of alum and sodium acetate are interfering with the mordant uptake, although this seems unlikely. Perhaps it’s a combination of the by-products with insect dyes, as we’ve noticed this same issue with cochineal. Perhaps something to explore in the future.

This method is the same as above, but we obtained pure aluminum acetate from a different supplier. The swatch here is quite pleasing but highlights how raw materials from different suppliers can materially alter the results.