Blocking crochet
Shape crochet with the care process permitted by the yarn, then measure the completely dry fabric.
Work the technique
Record the current measurements. Wet or dampen as directed, support the fabric, remove water gently and arrange its edges on a flat surface. Pin motifs to equal dimensions when joining a grid.
Try it on a sample
Finish two granny squares together and measure each side after drying.
Check and recover
Do not steam heat-sensitive yarn to force it into a different size. A border that ruffles needs a corrected stitch count rather than stronger stretching.