It all starts with two 8″ squares.

Bright Sisters has 320 half-square triangle (HST) units (3.5″ unfinished size) — not my favorite unit to cut and piece. Luckily for me, I discovered the Magic 8 Method (thank you, Karen Walker!) before I even bought the fabric for this quilt and I was able to plan my yardage and cutting diagrams to take advantage of this magical method. Visit Karen’s blog post or download Genius Hacks Every Quilter Should Know (thank you, Craftsy!) to get the full instructions and a few more excellent quilting tips. I’ll run through it quickly below. There’s also a Midnight Quilt Show episode where Angela Walters uses this method, if you want to see a video of it in action.

The thing that makes it a great approach for this quilt is that every matching set of HST units in Bright Sisters is a multiple of 8, so there was no waste and no units left over. It was meant to be!

You start by taking two 8″ squares, one in each color that you need for your HST unit, as shown above. Then you mark two diagonal lines across the wrong side of one of the squares.

Next, sew 1/4″ on either side of both lines, for a total of four seams.

When you have all four seams, you’re ready to cut the triangles apart. Simply cut vertically through the center where the seams cross, then without moving the fabric, cut horizontally.

When those two cuts are done, make two more cuts diagonally along the marked lines…

… and you’ll have eight half square triangles! It’s magic!

Or math. It could be math. But I prefer to think it’s magic.

Here I’m using a smaller cutting mat as a fake rotating mat, but after I did a couple of sets of these I broke down and ordered a real rotating mat. It made things easier.

I made my original 8″ squares slightly oversize for the 3″ finished size HSTs I needed — Karen Walker’s tutorial has directions for how to size your starting squares, and she recommends making them a little bigger than you need — so I still have to press and trim each one. (As we will discover in a later blog post, it’s a really good thing I did make them oversize…)

I have a nifty little June Tailor ruler that I love for this kind of trimming. You line up the unit so the diagonal seam matches the marking on the ruler, make sure the four edges extend past the horizontal marks and vertical cutting channels for the size you need, and trim the first two sides:

Then you turn the unit 90 degrees, line up the diagonal seam and the two trimmed edges, and cut again:

It made quick work of trimming 320 HST units!

One down, 319 to go! What’s your favorite method for making HST units? Any good tools you can recommend?

The previous post in this series was Bright Sisters: Drunkard’s Path Units. Next time, we’ll explore the consequences of a momentary lapse of attention I had while making these half-square triangles. Oops.