Ok so here is my example of overdying yarn. What’s overdying? Basically, it’s dying yarn that’s been dyed before. 

On the left is how the yarn originally looked, and on the right is after I dyed it over with black at 80%. 

Now, two things to consider: that type of yarn you’re working with, and the color you want to achieve. 

The yarn I had was 100% alpaca, which doesnt dye at well as, say, 100% wool. When dyeing alpaca it tends to be a little more pastel and undertoned than 100% pure color, even when using strong dyes. Which is fine by me most of the time. In this case though, the first time I dyed this yarn it turned out way too bright for my tastes, and I wanted to try overdying it to see what happens. 

The other thing to consider is color theory. You cant go from a dark color to a light color. That’s just not gonna happen. And you have to consider how colors work together as well so if you overdye a yellow with a blue, your end result will be a shade of green. 

My end result looks kinda like an oil slick in the dark when knitted up, which I really like!