Prism99

You spray starch after cutting the fabric? It's a risk. A lot depends on the fabric; some will not shrink, but some will and there's probably no good way to tell in advance. This is why it is not recommended to wash or spray starch pre-cuts (which are always unwashed fabrics).

Also, half square triangles are one of the worst cuts in terms of distortion problems. Shrinkage of 1/32" might not show up in cuts of 5" squares when put together, but that same shrinkage in cuts of small half-square triangles could well be disastrous.