Prism99

I will test a suspicious fabric (batik or not), but typically I do not prewash batiks. However, for the first wash of a quilt I take it to the laundromat and use their largest front-loader and Synthrapol. The large washer uses enough water to dilute any dye bleeds, and the Synthrapol suspends loose dye particles in the water so they go down the drain instead of settling into other quilt fabrics.

Color catchers are fine for catching small dye bleeds, but they are insufficient if you happen to have a fabric that bleeds a lot of dye into the water -- especially if you are using a domestic front-loader which does not use enough water to dilute a big dye bleed.

In my experience, batiks are no more or less likely to bleed than many other cotton fabrics. I think many years ago, when batiks first came on the market, the manufacturers were not as good about completely rinsing out excess dyes -- especially since those batiks probably originated in the native markets of Indonesia and Malaysia. Over the years, I think the process for making batik fabrics has become standardized to the same specifications used for other colored fabrics.

Edit: I should add that I prewash a fabric that seems to have excess dye, in part because I want to make sure that the problem is only excess dye that has not been rinsed out. Some "bleeders" were never properly set by the manufacturer and will never stop bleeding. Those I don't want to use in my quilts.

The main reason I choose to prewash a fabric is when it is a cheaper quality fabric, in order to tighten up the weave. I recently bought some wonderful solid red fabric at JoAnn's on sale for about $2.50/yard, along with some novelty children's fabric that was really cute. I prewashed both fabrics separately. Neither fabric bled, but I liked the way that prewashing tightened up the weave so they looked like much better quality fabrics.