One strand from an embroidery floss. It makes all the difference!
I recently acquired a new domain name, and thus wanted to create a new QR code patch for the address. I’ve made some in the past that work near flawlessly; however, this weekend I stitched the patch on the left, and to my dismay, my QR code reader would not read it. At first I thought I had misspelled the address but it wasn’t even recognizing the image as a QR code. My google reader kept calling it a “Flash tag” or bringing up “similar” B&W images.
Two threads from a strand usually are enough for normal cross stitch… it can look slightly sparse but I think less threads make a cleaner image. I’ve learned through this experience that at least three are necessary for the QR code to be functional.