Berry Dyes, Wash and Light Fastness Tested

"I can't remember a year when the blackberries ripened so early. And there are still plenty more to come. Lovely ones, too." 
My companion barely spared them a glance, having other fruit in mind. I watched her pick her way up a branch of blackthorn, sheer madness, but you have to admire that kind of commitment to sloe gin. 
"Mind your fleece on those thorns, Elinor."
She waved a hoof and chucked a ripe sloe into the basket.
"Who dares, wins, Beaut."
I suppose I'm just as fanatical about plant dyeing, though I decided long ago that the only purpose for picking fruit should be with a view to eating it.

Early experience of berry dyes left me soured with the bitterness of pretty pink knitting gone beige by Christmas. At this time of year, Pinterest is simply laden down with fabulous pictures of berry dyed yarn. Planning to make some berry robb, I went back to check the recipe on a blog I wrote five years ago, when the disappointment was still fresh. My companion joined me and we were soon scanning the latest berry dye images to arrive on the computer. 
"It's such a shame. Those colours are going to fade, no matter what they say online."
Elinor looked at my purple stained fingers.
"To be fair, Beaut, most of your dyework was pretty crap, back in the day. Go on, have another go, I'll even give you some sloes, there's plenty left over."
I had to wonder, was I wrong to condemn berry dyes out of hand? Could all these people really be wasting their time? This year of all years, it wouldn't be such a big deal to do a proper trial, trying to avoid beginner's mistakes.

One thing I've learned is the most effective way to mordant fibres is by heating them for an hour in a 10% alum solution. Dyers have been using alum for several thousand years. Another way to improve colour depth and fastness is to use lots of plant material to weight of fibre. With this in mind, I simmered 200g fruit for each 10g sample, a ratio of 20:1. I decided to dye wool and silk blend fibre tops and my test subjects were blackberries, elderberries and sloes, (since Elinor was offering, though of course, sloes are stone fruit, rather than berries.)

The simmer to extract the dye was kept well below the boil, as I have found high temperatures can destroy some natural blues. Purple might be the result of a mixture of red and blue dye molecules, so a cooler dye bath ought to give berries the best chance. After mashing the stewed fruit in my three pots, leaving it to cool and sieving out the juice, I gently heated the samples for an hour and left them to cool in their pots for 24 hours. Another major error I used to make was whipping wool out of the pot pronto, just to see what colour it had gone.

I now realise that during a long soak, fibres are able take up considerably more colour than they absorb during the initial simmering phase. To avoid bleaching out fresh dye, my samples were dried out of direct sunlight and to avoid washing out any as yet unfixed colour, they were left without being rinsed. I did tease out a portion of the fibres from each sample to spin a little skein of yarn.
These are my glamour shots of the results, purple from blackberries, pink from sloes, with the elderberries giving a colour somewhere in between. All the pictures were taken a couple of days after dyeing.

To test lightfastness, I wrapped a few turns of each dyed yarn around some white card, slid half of the card inside a fold of black card to exclude light and taped it against the skylight for a week. It was a wet, grey week, with no sunny days at all. In the meantime, I tested wash fastness by wetfelting some of the dyed fibres around a soap. Here's a link to the method, it involved about fifteen minutes of rubbing the wetted fibres against a bar of Dove soap with half a dozen plunges from hot to cold water. To my surprise, I didn't see any colour wash out of the fibre, there was no pink discoloration of the lather or rinse water.

Sadly, this is how my felted soap turned out. Sloe pink had turned beige, elderberry went brownish, only blackberry held much purple.

"There you go, see, the blackberry dye is alright." My companion has become relentlessly cheerful. Suspecting the sloe gin might already be going into her tea, I sighed, smiled and added an extra stripe of blackberry round my felted soap.

Given the lousy weather we have been having, lightfastness was not by any means an extreme test. After a week, this is how the card looked, shown together with the little skeins of yarn, which had been kept in a drawer. The effect of light exposure was similar to washing.

"I'll have to use that soap up quickly, Elinor. Now the sun is shining through the bathroom window, it will soon go completely beige."
"Oh, don't be so negative, just bathe by candlelight. Anyway, it's all your own fault for not adding any vinegar to the dye bath. Everybody says that fixes berry dyes." 
"Now I know you've been on the gin. VINEGAR IS NOT A MORDANT!!!!!"
"Chill out, Beaut, my body is a temple. While I'm waiting for those sloes to ferment, I've taken up yoga again. Don't stress over lightfastness, rejoice in nature, join me in a sun salutation. Ooo, you've gone all red in the face."

I took the dog for a walk and had a think about things. Acidity does change some plant dye colours, quite a few of them are sensitive to pH.  I do know vinegar isn't going to fix natural dyes onto fibres, but it might affect how they look. I put vinegar and water into one jam jar and dissolved a little soda ash in another, to make an alkaline modifier.

Small samples of the dyed fibres were left to soak for twenty minutes in each jar. Once they had dried, I laid them out, vinegar acidic soak on the left, unmodified fibres in the middle and soda ash alkaline soak on the right. I don't think the vinegar deepened the colour perceptibly. Berries are naturally acidic, it gives them flavour. On a guess, the berry dye bath was already acidic. Washing the fibres with soap while wet felting probably reduced the pH toward neutral and that was why the colours dimmed so quickly, even though no dye appeared to rinse out. Alkali did indeed shift the colour, look at that green, much the same modification as with pink hollyhock dye.

"See, Elinor. More acidity didn't even alter the berry dye colours. All those people putting instructions online about adding vinegar really are sending each other on a hiding to nowhere."
I got out my camera and showed her a couple of photos. "It's all a matter of what you choose to share, a well staged first impression or an evaluation under test conditions."

"Life's an illusion, Beaut. Live the dream. By the way, did you remember to add salt to the dye bath?"