I followed the instructions I found here. All you need is some permanent markers (we got some at the local dollar store), some rubbing alcohol (from the pharmacy), and a dropper (we got a 2-pack on sale at Michael's last week). And some plain shirts (we got ours at Joe Fresh).
Draw a circle of dots, then another circle of dots around it in a different colour, and then another around that (you could keep going as many times as you like, really).
Then use the dropper to add a squirt of rubbing alcohol in the centre. As the alcohol is absorbed into the fabric, it catches the colours and they bleed outwards in a circle.
That's it! They were so fun and simple to make, even Daddy Pea got in on the crafting action!
Tips: Put a piece of cardboard or something inside the shirt so the colours don't bleed through to the back of the shirt (we used the pieces of cardboard that came inside the onesies packaging). And hang them up to dry so that the front and backs don't touch. We hung them over lamps and the seat of the exercise bike! You could also just leave them drying flat on the table, but we needed the table space.
Then I ironed them to set the colours. I don't think I did that very well, though, and the lighter colours (yellow and, to a lesser extent, the pink) did wash out somewhat. The dark colours stayed better. The instructions we used suggested that cheap-o markers worked best for 'bleeding', but perhaps real Sharpie markers would have had better staying power? If you try it, let me know!
And here are the results - pretty darned fantastic, if I do say so myself!
For another fun way to make DIY t-shirts, check out this link!