a tale of two batts

You probably remember this blue/green batt that I made a few weeks ago.

I dyed 50 grams of merino/bamboo top then carded the colors together to make the batts. Normally when I dye, I play mad scientist and use the colors as they appeal to me without worrying about reproducing a colorway. For this batt I decided to record the colors in case I liked how the sample turned out.

So here it is a few weeks later and I decided to dye some more to make enough yarn for socks. I started with 50 g of the same top, and prepared the dye solutions in the same way (or so I thought). This is what I got.
Not even close. Pretty but not a duplicate of the first sample at all. Several things are likely to blame. If I remember correctly (I did not write these things down in my notes), I placed half of the fiber in each of two crockpots the first time and only used one crockpot this time. I also must have warmed the dyes the first time and not the second. And I must not have waited for the dye bath to reach the same temperature when I added the dye. Now I know that to reproduce a colorway I must record EVERYTHING, not just the dye colors and dilutions.

Here are the two batts together.
Besides the obvious color difference there is also a value difference as you can see when I make the photo black and white with my photo software.
I sampled a bit of spun singles from each and plied them together. The darker yarn took over and the pale blue pretty much disappeared visually. So I carded the darker batt with an equal amount of white fiber. Here you can see the lightened result beside the dark one, in color then in black and white.
And all three together.
Hmm, now I have three different values. Hard to believe that all three came from the same colors and fiber. I'm stymied about how to proceed and I guess I will have to do more sampling. I could blend all of the darker stuff with white and then ply it with the blue. Or do a 3 ply and spin a singles with each of the batts. Or try to reproduce the first batt again and see if I can come closer.

Now I really know why you should buy all of the same dye lot before starting a knitting project. I will use a larger pot and dye all my fiber at the same time in the future.