Always prewash your items. Then start with a wet shirt (or article of clothing), then tie it, then soak it in soda ash before dyeing. Use dye with water mixed with urea.
Fold your shirt in half first for a double spiral variation:
This is my first double spiral. I used turquoise base and the spirals have black and bit of purple. But I didn't use the technique in the diagram above. I did two, side by side spirals when I folded it.
Double Spiral using the technique above.
Shirt had some polyester, so it's not very vivid.
Do NOT remove the rubber bands or string until AFTER you've put the garment through the rinse in the washing machine. When you're all done and the shirt is dry, iron with a hot IRON.