Should You Block Your Swatch?
Don't “Block” Your Swatch. It Doesn't Matter What Gauge You Can Pin Your Swatch To. What Matters Is the Gauge Your Swatch Has When It's Been Washed and Laid...
How does blocking affect gauge?
And since blocking knitted fabric can significantly affect your final gauge measurement (as well as the hand of your fabric), be sure to employ the same blocking techniques (steaming, wet-blocking, etc.) that you'll use on your finished garment. ... Resist the urge to measure your gauge before your swatch is bound off.
Does gauge change after blocking?
The gauge changed very little after steam blocking (mostly no change in stitch gauge, though some showed shrinkage in row gauge) but they all grew after wet-blocking (between 2% and 7%).