I've tried acorns to get black before , but so far my experience, it has almost always been more like grey. I never get the intensity. But grey is ok.
You can find tutorials on the web by searching for dyeing black with acorns. Here is one. And another. There are varying approaches but all basically rely on the tannin/ iron chemical reaction. That's the idea. The concept.
There are usually 3 pots on the stove during the colder months. Walnut, acorn, pomegranate. All tannin rich liquids to play with. So, I asked myself what if I tried all 3, using the same concept. A dip in the dye. A dip in the iron water. Silk this time.
Oh yeah! These were washed and dried. Honestly I like the pomegranate. But they are all different which offers a range. These were short dips. Still playing .
The pomegranate is still giving me that "slate" black. Glorious.
On linen below:
A lot of times, when I "dye black", I am really talking about darkening. I often use the over dye concept. Darkening or what I call Blackening a color to suit my needs. Any very deep color looks black in contrast to white or a very light shade. And by over-dyeing, you get what I see as a full spectrum of blacks. (darks)
I do get black marks on cloth from a tin can. So I think this is an alternative, blackening my threads and scraps by repeating the process until it is dark enough. Full contact with the can in a tannin solution , will get very black of left long enough. I tend to do it over and over, layering, gradually building with the can and with dye. One over the other.
Below, just white thread pressed to a can, soaked in acorn liquid. About 15 minutes. I have others sitting and waiting.
Some brights dipped in the indigo vat about 10 times.
But then, as one thing always leads to another, I asked myslef, what if the tannin /iron reaction would work as an over dye. And indeed it did.
I wonder if very strong tea would work?