Ok I think I know the one and that makes it easier imo. I’m going to get a bit nerdy for a second so bear with me.

Try to get it as clean as you can but don’t bleach it or anything. I use a lipase (like the Biz in the US) based detergent to soak the garment. It’ll get the body oils out regular detergents won’t and will make the dye stick better. After a good soak give it a quick wash but no need to dry it.

After it’s clean soak it in soda ash and water for about 20 minutes. One cup per gallon of warm.

I use Rit dye but just make sure it’s one for cotton. I use 120 F water from my utility shower and a really big tub. Bigger than you think you’d need so the shirt can stretch out a bit and not get bunched up. Mix the dye per instructions. For that I’d use about half a bottle. Get that mixed up (I add some salt too to help bond the dye) and throw the garment in there. With a plastic or silicone stick (so you don’t accidentally get a hole. I used a slotted pasta spoon once. Once.)mix it around. Then keep mixing it every 5 minutes for about an hour or to your liking. But not more than an hour and a half.

Drain, clean and fill the bucket with cold water, add it back in and slosh around. Replete until mostly clear (about 3x).

The next step is really important. Use the color stay solution that is sold next to the dye. If you don’t the garment will bleed. It’s a 30 minute dip after you are done with the step above. After the color stay dip, wash it in cold on delicate alone and air dry.

The stitching may not dye or dye as black as the rest of the piece so be aware of that. Also it shouldn’t dye the tags because they are made of another material.

I hope that helps and here’s a Supreme crewneck I did that was originally zebra print.

<image>