I'm not an experienced dyer, but I must say that I have been very pleasantly surprised by the bright colours I have managed to achieve with natural(ie vegetable dyes). Brazilwood on silk is a lovely bright pink, and broom can achieve lovely bright, and even golden yellows. (I must admit my few attempt with woad and madder still require practice though!)What was even more 'surprising' was seeing textiles in the V&A which haven't been exposed to excessive light/washing - the colours are all bright, deep, and really beautiful. Having not had much success in dyeing deep colours, it was lovely to see blues and reds and greens as dark and bright as I would expect to see in any modern shop.
Yes, vegetable dyes can fade faster - but, to be fair, medieval clothes weren't subjected to high spin washing cycles and chemical detergents either. Items which were in the home, or church (as many of the V&A items) would not have been subjected to excessive daylight either. The few items I have made from hand dyed silk have so far lasted well (girdles, purses etc) three years on from my first attempt. Gentle hand washing ensures colours stay, and correct dyeing 'should' mean that colours do not run when wet.
Likewise, as a comparison, I have seen many Victorian items which used the 'new' chemical dyes, which are faded. I have also seen some which haven't been over exposed to light, or excessive washing - showing bright and intense colours. The contrast is just as great in these items, so perhaps it is simply the age of the items which cause us to assume that colours were so different then as now.
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Gina-b Silkwork & Passementerie
Tak v Bowes Departed
Soper Lane