I signed up for the Free Craftsy 2015 Summer Block of the Month.  The pattern is Night Stars, by Kimberly Einmo, and has a large star in the middle surrounded by a variety of different traditional stars.  July’s class focused on sawtooth star variations.   I had lots of practice with these on my last QOV quilt!

They look nice, but I was frustrated since all of my blocks came out about 1/8″ too small.  This isn’t usually an issue for me using a scant 1/4″ foot.  My theory is that the batik fabric (new for me), plus the thread thickness I was using was the culprit.

This table I found online supports my theory.
*  Remember, higher numbers represent finer threads.
** Some of these threads are 2 ply, some 3

Equivalent Thread sizes… 
Aurifil 50/2 – 25
Aurifil 40/2 – 20
Gutermann 50/3 – 17
Connecting Threads 50/3 – 17
Coats & Clark/Star 50/3 – 17
Mettler 50/3 – 17
King Tut 40/3 – 13 “

I have ordered some 40 wt. and 50 wt. Aurifil thread to see if it makes a difference.  All of my July blocks were stitched using 100% cotton, Gutermann 50 weight.  If the chart below is correct, the Aurifil thread may be a little finer.  A fellow class member used the Aurifil 50 wt, and her blocks were slightly large, so my first test will be with Aurifil 40 weight thread.

After I see the results in practice for August, I might have to put some of these under a microscope and rap get some photographs (just for fun).  Stay tuned!