Overdyeing Grey Yarn with Yellow Plant Dyes

"See? Yellow and black does make green." This was the conclusion of a vexatious day, spent with me telling Elinor lots of natural dyers had said that yellow plant dyes turn grey yarn green and her insisting that everybody knows yellow and blue make green. My companion studied the saucer of acrylic paints.
"Reminds me of nappies."

"Personally, Elinor, I prefer these colours to the blue greens." I was quite intrigued to find that though the tube of 'Mars Black' acrylic paint had dried into lumps, brushing it briskly into fresh Cadmium Yellow evidently did produce shades of green, albeit of the organic variety. My companion muttered something about cow dung, or it could have been horse shit.

Last week, weld and meadowsweet dye baths both turned some synthetically dyed light and dark grey DROPS merino yarn rather green and though I'd believed this must be because of blue dye within the grey yarn, several other dyers commented that they had noticed the same phenomenon. This week, I wanted to try dyeing naturally grey wool.

Unfortunately, my yarn stash mainly contains greys that include strong shades of faun to chocolate brown.
"It's not easy to come by a pure grey fleece, Beaut." My companion ran a loving hoof over her own lustrous Gotland locks and gave me a pointed look. "Hand spinners have been known to go to desperate lengths to get hold of one."
Down the bottom of the box, I found a skein of Romney X Shetland in mottled grey with no noticeable brown. I'd spun it in the grease ages ago and been a bit disappointed at how rough it turned out.

Mordanted with 10% alum, two skeins of about 50g Romney X Shetland went into the same baths of weld and meadowsweet I made last week. In the weld bath, the last 100g of the DROPS yarn was also dyed for a direct comparison.

At the top of this picture, samples from the first use of the weld bath show the strongest colours. In the middle are skeins of white, then light and dark grey synthetically dyed DROPS yarn. At the bottom is the naturally grey Romney X Shetland. With the weaker yellow from the second use of the weld dye bath, the greening effect of overdyeing the grey yarns is even more pronounced and has proved very similar on both the synthetic and natural grey bases.

Such a qualitative shift from one colour to another hasn't happened when I've overdyed shades of grey wool to blue with indigo or red with madder.
"Soon there'll be daffodils and dandelions and new tree leaves all giving yellow dyes, but I shall have no grey handspun to experiment on."
"Well, Beaut, after last week, I wouldn't recommend you using any more of that iron."

Modifying with iron would be my usual way of saddening a yellow plant dye on a white yarn toward green. I tried using iron on two skeins of white and grey DROPS yarn that had been dyed in the first weld dye bath and made rather a hash of it. Not having used my iron solution for months, I only added a little splash in case it had dissolved a lot of rust in the interval and grown more concentrated, then after ten minutes heating, when nothing seemed to be happening, I added another slug of iron straight onto the wool in the pot, overdid it, tried to cool the bath and rinse the yarn quickly, ending up with unevenly variegated and rather dark iron modified colours. As someone suggested on Ravelry, starting with a grey base would obviate any need to modify yellow dyes with iron, which, even in better hands than mine, will tend to weaken and roughen wool fibres.

In last week's comments, Freyalyn advised on what to do if you do want the deeper tones of yellow over grey and you don't want green - start with a warmer, more orange-yellow plant dye. The skein of Romney X Shetland on the right of this picture, which went into the meadowsweet dye pot, came out quite differently to one on the left from the weld. I held up the two skeins to my face.
"I do like this darkened yellow, it's just that reliable sources of green dyes aren't so easy to find. When I resort to indigo overdyeing, my results are so unpredictable."
"Fair play, Beaut, I can see the problem. Yellow really doesn't suit you - makes you look like something the dog dragged in."
I put the dyed skeins down.
"I'd love to do more with yellow dyes on grey. It was a good grey, that Romney X Shetland fleece, shame it wasn't softer." 

"Might have come out nicer if you'd made more effort with preparing the fleece - never your strong suit, is it Beaut?"
"True enough."
"This might resolve your difficulties." Elinor showed me a photo on UK Spinners.
"What is it?"
"Someone's selling a whole grey Merino sheep fleece from Yorkshire. Bound to be soft and fine, but it's already been washed and carded by a local mill, so even you can't felt it before you try spinning."
I really shouldn't have bought it. But I'm so glad I did. 
And Elinor says she'll sleep more soundly knowing I have my own grey fleece.