In this case "heat distress" does not refer to the way everybody in Austin feels about the arrival of summer both with a bang (the sun) and a whimper (the rest of us). It's the fabric that we're going to make seriously unhappy.
Start by laying down a base of sheer synthetic fabrics. (You can use solid synthetics too, as long as they're something that melts under the heat gun; but I prefer to stick to sheers here.) It's best if you choose analogous colors here that will layer well, since you do want to let the pieces overlap and blend. When the sandwich is made, stitch, rinse, and dry as usual.
Here's the starting point. Kind of boring, isn't it?
I've stitched a larger grid than usual - lines about 3/4" apart - to give the fabrics plenty of room to move and crinkle while they're being zapped.
Next step: Put the fabric on a heat-resistant surface like a ceramic tile or a concrete driveway and zap it lightly with the heat gun. (NOT a paint stripping heat gun from the hardware store - the kind of heat tool you find in crafts stores for melting embossing powder. We want to distress the fabric, not incinerate it.)
Even with the lower-power heat tool it's easy to go to far and wind up with a shriveled, plastic-hard blob. So work slowly, moving the heat gun to a new area every time the fabric you're heating begins to react, and maybe stop after the first few passes to evaluate how it's going.
This is more interesting than the original, but it still has a way to go. Back to the ceramic tile and heat gun!
Now this is a nice lacy fabric. Two of the synthetics reacted in particularly interesting ways, and I look forward to playing with them more after this project of samples and variations is done.
One fabric I used was a very sheer synthetic overprinted with a gold metallic grid. The sheer parts vanished almost completely and the grid remained.
Another fabric was snipped from one of the super-cheap, three-dollar saris I bought in India. This stuff melted in a very lacy way, which not all synthetics do; some of them just curl up and shrivel into hard beads.