History Boletes Itself: Purples to Dye For

This blog entry accompanies Episode 6 of the podcast. It deals directly with the content of the episode.

For those of you interested in more of the physics of color, I highly recommend PhysicsClassroom.com. The lessons are very well written and accessible, and come with legitimately fun activities to test comprehension. Find out more about the wave nature of photons or how light interacts with objects. Or just skip ahead to color mixing like I did, because colors are pretty!

Speaking of colors…

“Royal purple” now doesn’t mean the same thing it did three thousand years ago. The modern color is a much darker, bluer purple than the apparent original. Here is a swatch dyed with the snail extraction.

The image has been cropped from its original size (source).

And here’s the average “Royal Purple” from a Google Image search.


And speaking of purple…

Aden Brown (Massachusetts) sent in this picture of the Cortinarius iodes, which is the same one he talks about in the episode’s intermission.

Aden Brown (2).jpg

You know what else is pretty? Leena Riihivilla’s amazingly varied yarn.

Using different mordants like alum, iron and rhubarb, and different acidity (pH), one mushroom or lichen gives Leena amazingly different colors. Leena writes in both English and Finnish on her blog, which is an incredible read!

Here’s a brilliantly blue Sarcodon squamosus, a species Leena loves to experiment with.


By using ammonia, rhubarb, or washing soda mordants and dyeing multiple skeins (bundles) in the same bath at different times, Leena has gotten twelve colors from one batch of S. squamosus.


To see what inputs gave which color, visit Leena’s blog page for the experiment.

There’s a stark difference in how well some dyes cling to the yarn depending on how heat is applied. All the yarn in the image below was dyed with Hydnellum suaveolens. The bright turquoise was a result of boiling the yarn with the mushroom and ammonia. The pale green is the result of solar dyeing with this mushroom, essentially leaving the ammonia, mushroom, and yarn in a jar in full sun.


For more details, visit the experiment post.

The final example for this post (but not the last one Leena has, by far!) is an experiment with the Tinder Polypore, Fomes fomentarius. By varying acidity (pH), the age of the polypores used in dyeing, and use of mordant, Leena captured eight colors.


She found that higher pH gives a stronger yellow, while more acidic dyebaths give stronger browns. See her process here.

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