Coreopsis Tinctoria Dye, Modifying pH, Adding Iron and Copper

I first grew Coreopsis tinctoria plants and started dyeing with them in 2013 and I've been saving seed to grow them again every year since. I'm sure that when I started, the flowers were mostly yellow with deep red centres, just a few plants having petals entirely dark red. I tended to ear mark those to save seeds from, after discovering in 2014 that their dye seemed deeper. 

This summer's flowers appear to have larger red centres, with more raggedy edges and some have tiger spotting or little extra petals twisting out of their centres. I think these changes look rather fabulous and guess the plants have hybridised somehow. Botany is not my subject. There can be no reason to think their dye properties might have changed, though I have been half tempted to blame the flowers for some recent unplanned results.

Coreopsis tinctoria is a lovely annual dye plant. Buds bulge and burst open so profusely, it is hard to pick often enough to keep the plants from going to seed. Simmer an equal weight of fresh flowers with mordanted wool, silk or cotton to get orange/bronze colours. Fill a solar jar with flowers and mordanted wool and it will only take a few weeks warmth for the dye to be taken up.

Rediscovering a jar of coreopsis and merino which had been brewing rather longer, in fact, forgotten since last summer, I emptied it out onto the lawn.
"Ych y fi! Has the dog been sick?" My companion, Elinor Gotland, gave the contents of the jar a wide berth. Though the flowers had disintegrated, they hadn't gone smelly and the merino was absolutely fine after a couple of rinses.

Spinning along with the DIY and Dye team on Ravelry for this year's Tour de Fleece I thought dyeing my Beulah yarn a glorious orange like this would be a splendid result to show off. Hoping to impress, I used twice the weight of flowers to wool and knowing coreopsis dye is pH sensitive, I added enough dissolved soda ash to make the dye bath alkaline, about pH 8. 

"That yarn looks less of an orange, more of a raspberry and you look like you've been sucking a lemon, Beaut." 
"I must have overdone it with the alkali. "
"I'd say sour beats sweet with coreopsis dye." Elinor strolled blithely past the heaps of wool, leaving me sighing bitterly and soaking a length of the yarn in vinegar. It had little effect. 

Might as well pursue my original plan to modify one skein with a brief heating in iron solution - top of photo, and another in copper - middle of photo. I tested a pinch of the merino at the same time. None of the modified versions are a patch on the classic orange - bottom right.

Ah well, I thought, at least I have been spinning a steady ten rolags of Beulah wool every night and the coreopsis will have more flowers tomorrow. Simmering another two skeins in a new bath - AAAGGH .... NO - the result was worse still - greenish brown?? (see right of photo) Presumably I didn't scrub the pot well enough and it still had traces of iron in it. Enough to spoil the orange, at any rate. The pink skein in the photo had been dyed with birch bark and while I was modifying that to purple in a copper solution - far left of photo, I modified the second greenish coreopsis skein, turning it chestnut brown. What no fruity or nutty remarks? Where had Elinor got to? 

We didn't meet again til the evening. Coming in with my watering can, I found her sunning herself in the greenhouse.
"I noticed you'd taken another fall in your Tour de Fleece, Beaut, still, no bones broken are there? I've put some of the Beulah locks in this jar, mixed up with the latest coreopsis flowers. You can spin them another time. Come on, pick yourself up, pedal that wheel, get back on your bike. It's a rather fine view from arriere du peloton."
"Thanks, Elinor, you're a pal."
"Hmmm. Press on with the next stage and you might even win the beige jersey."