Black Dye from Peat Bogs

I was wondering how black dyed was obtained before synthetic dyes were derived from fossil fuel.  According to dye artist India Flint,

In parts of Scandinavia, the traditional thick woollen skirts of regional costumes were dyed by extended immersion in peat bogs.  The process sometimes took up to two years, as the cloth was immersed in the bog, left to soak and occasionally aired, possibly to encourage oxidisation.  The acidic nature of the bog would have acted as a wool conditioner, helping to soften the coarse fibres as the cloth turned from a warm golden brown to (eventually) a rich black.
-India Flint, Eco Colour: Botanical Dyes for Beautiful Textiles (Loveland, CO: Interweave Press, 2010), p. 22.

It's interesting about a bog soak used to condition wool.  As a handspinner, I am concerned about getting wool that is soft before I spin it, wool from flocks bred and raised for good quality.  I assume that the qualities of the wool will stay the same once it's made into fabric.

Most fibre artists today want soft wool.  Most people who wear clothes prefer soft fabric.  And then there I am, half a year after purchase, scraping pills off a store-bought lambswool sweater.  It's a tradeoff.  Maybe bog water gets you fabric that's both durable and softened.

Two years to wait until you wear a skirt.  What a different mindset from today.