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This will loosen the fibers of your suit and allow the dye to be more effective. For the best results, choose a white or light colored nylon suit. Use garbage bags, old towels, or an old tablecloth to protect surfaces. Work outside if possible. Acid dye will give you the best results. Choose one color for a monochrome design, or multiple colors for a more traditional tie dye look. Use rubber gloves to protect your skin while preparing the dye and while dyeing your swimsuit. Pull up small pieces of the fabric about 1 to 2 inches (2.5 to 5.1 cm) apart and tie the material off with your rubber bands. Create interesting patterns by varying the amount of fabric you tie off and/or the spacing between each section. The longer you leave the suit in place, the darker the color will be. Rotate to a new section and a new color until the whole suit is covered with dye.  Dyeing time can be anywhere between 5 and 20 minutes depending on the base color of the suit and how dark of a shade you want. When using multiple colors, expect some of the colors to run together at the edges and create a new color. This will add more interest and color to your suit and is preferable to leaving areas without dye coverage. If you are using only one color, you can use a large dye bath and fully submerge the suit once you've tied it off with rubber bands. When the water runs clear, wrap the suit in an old towel to remove any excess water and dye. Hang to dry.  Place an old towel underneath the suit as it drys to catch any excess dye. The first few times the suit is washed, wash it alone in case it bleeds.

Summary:
Soak your pre-cleaned swimsuit in warm water. Cover your work area so the dye doesn't stain it. Prepare your dye as directed by the manufacturer. Create your tie dye pattern by gathering and twisting sections of your suit. Dip sections of the suit into the assorted colors you've selected. Take the rubber bands off and rinse the suit in hot water.