I mentioned before that the reason I have moved away from working with plant dyes and stains for the most part is due to poor lightfastness. It all fades. Everything. Some last much longer than others, of course, and there are things you can do to help it last longer, but organic (plant based) pigments will never retain color like inorganic (earth/mineral based) pigments do, which is what I primarily use now - with a few exceptions.
Over the last several months, I have tested many different botanical wood dyes and stains as well as methods for getting the deepest, most lightfast color.
First up is a test I did with a plant material that I already knew is not very lightfast based on my prior tests on wool. I was primarily testing to see which method could increase lightfastness. Dye stuff used was painted mountain corn husks heated in water. It dyes a lovely pink on wool or wood.
Samples are as follows:
- None - wood was soaked in concentrated dye bath for 6 hours
- Alum - wood was first soaked in alum, allowed to dry and then soaked in concentrated dye bath for 6 hours
- Soy - wood was first soaked in soy milk, allowed to dry and then soaked in concentrated dye bath for 6 hours
- Lake - a botanical lake pigment was made from the concentrated dye bath, filtered, dried, and then pigment used to make a watercolor paint which was painted on the wood
The soy and lake gives the deepest color, however, the lake pigment was just painted once. Layers of color could have been added, making it even more saturated.
These four samples were half covered in card stock (I use inside out cereal boxes, they are perfect for this) and left in a sunny south facing window for just a mere three weeks.
The none and alum samples faded to nothing. The exposed soy faded to brown, while the lake pigment paint retained the most color, with very little fading. Make no mistake though, another few weeks and the lake pigment would have faded considerably! This dye material is not lightfast, which as I mentioned, I knew going in - that was to test to see which method would help. Lake pigments for the win!
After another few weeks just sitting on my shelf, out of direct sun (image above) they have continued to fade.
I have since tested this with a number of other plant dye materials and the lakes always improve both the saturation and the lightfastness of the color. Soy always fades to a brownish version of itself.
Here is another lightfast test, this time with a dye material that is much, much more lightfast. I also wanted to test these four methods using a dye that I know lasts a long time. Walnut hulls heated in water.
Note that unlike the three weeks in the sun for the pink corn husks, these were left for over three months. There is a reason walnut stain is a thing. It works. Once again, the lake pigment was the most saturated but all four methods show very little fading.
By doing these tests over the last many months I have a palette that only includes the most lightfast organic pigments and only using them in the form of lakes. Honestly, though, there aren't too many. Indigo is one, although it is treated in a special way by extracting the pigment and creating maya blue for paint.
PS - Yes, the type of wood used may affect the result. Oak is much higher in tannins than pine, for example, and a higher tannin content has a tendency to turn colors dingy and brown, rather like what happens in my soy samples. Samples above are pine. I have had similar results on poplar, aspen and birch but I have not tested other wood types since I do not work with them as often.