Links to supplies I use:
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If you want to create geode style tie dye, I highly recommend using sinew (waxed thread). Some people use rubber bands but I found that to be tedious and time consuming. I've also been able to use zip ties but those are difficult to remove and wasteful.
I usually prefer ice dye, but when I want to use liquid dye, I love this small dye application bottles. The tips are tiny, allowing you to poke them into the folds of the fabric, making sure it's well saturated.
Soda ash is used with fiber reactive procion dye, to "fix" the color (make it permanent). When presoaking with soda ash, use 1 cup of soda ash with 1 gallon of warm water. You can skip the presoaking step and just sprinkle the powder on top of the ice, when ice dyeing.
The first link is to Jacquard's procion dye, on Amazon. I have used this brand of dye and it's works well. It's more expensive than Dharma's dye, but it can arrive faster because of prime. Dharma's fiber reactive procion dye comes in many colors and they have great customer service.