I originally tried extracting from 240g of husks. After smashing up they were simmered for about 2 hours than left overnight before another 30min simmer. The resulting dye liquid was a rather disappointing pale brown.
Undaunted I then carried out a test dye using 4x15g alum mordanted and 4x15g unmordanted Shetland fibre. After a couple of hours simmering the results were somewhat underwhelming so I left to soak overnight.
Sadly there seemed little difference the following day so I split the dye solution and tried alkali, copper and iron modifiers. After rinsing and drying the results were:
(left-unmordnted, right-mordanted, top-bottom, no modifier, alkali, copper, iron)
The results are that most samples are an unremarkable tan with slightly stronger colours on the alum-mordanted fibre. Only iron significantly altered the colour giving a pale grey suggesting that the brown was down to tannin.
Given the effort to recover this colour I have to say that these husks weren’t worth the effort, given the stronger tannins you can get from oak galls and bramble which are also available throughout the year.