Gauge Swatch Questions

[catwoman]

Hi.   I was wondering why some people when their done with making a swatch they pin it up and spray water on it and check the gauge again?.

Does a person have to do that?

[Granny Square]

I use acrylic most of the time, and never block it (no point with acrylic).  It does make a difference if you are using wool or some other natural fibers.  I was really shocked when I made something with wool and was trying to sew a seam, then I decided to block it and try again - whoa, what a difference.  But acrylic, nah.