Originally Posted by
brushandthimble
My guess would be would not enough seam allowance width on both pieces of fabric.
That's exactly what happened. I made the HSTs by placing the colored fabric on top of the white, sewing them together then cutting them apart and I cut the seam allowance on this piece shorter than 1/4". It is also the bias edge so it isn't as strong as the other edges. When I washed it, there was pulling on this seam and it gave way by fraying.