What I’ve noticed with nearly every new pattern I attempt or create is that a patchwork alphabet is pretty much impossible to make without using half-square triangles! They are the workhorse block for making diagonal lines, and even curves become less unwieldy with two or three half-square triangles thrown in. The half-square triangle is suitable for the adventurous or confident advanced beginner, but not because it’s tricky, because it’s not tricky! It’s just a bit fiddly with the precise measuring and the stitching across those pointy bits. If you can sew a straight line and you’re not afraid to take a couple of tries thanks to wonky measuring or thread barf (both of which I’ll tell you how to avoid!), you can sew half-square triangles. Here’s how!
Materials
To make two half-square triangles, you will need:
2 fabric squares, cut to 1″ bigger than you want your finished half-square triangle block to be water-soluble or heat-erasable pen. I LOVE these Frixion heat-erasable pens (here’s another project where they come in super handy!), but be warned that they will leave a white mark on some dyes. It doesn’t matter here, but test them on any fabric that you really can’t afford the marks to show on. iron cutting and sewing supplies. I’m sewing eensy 1″ finished half-square triangles, so I’m using Microtex Sharp sewing needles. A universal needle should be fine for larger blocks, but if you’re having trouble with the needle piercing the fabric as you begin sewing that first corner, a Microtex needle would be a good idea for you, too.
Step 1: Mark and Sew.
Put two squares of fabric, each 1″ larger than you want your finished block to be, right sides together. Use a ruler, ideally a clear quilting ruler, to help you draw a line with your water-soluble or heat-erasable pen that runs precisely from one corner to another. Notice that I’m just the tiniest bit off in the photo above–this step is very fiddly! If you’re also the tiniest bit off you will have the tiniest bit of wiggle room at the end when you trim the block to size, but if you’re more than the tiniest bit off, it’s probably best to erase your mark and take another run at it. The second most fiddly bit comes next: you need to sew a straight line EXACTLY .25″ from that line on both sides. First, make sure that you know exactly how to achieve that quarter-inch seam on your sewing machine. For me, it’s moving my needle all the way to the right or left, then lining up the edge of the fabric with that outside edge of my presser foot. But for you, it might be different! The best way to verify your measurement is to put the needle down, then use your ruler to literally measure where that quarter-inch hits on your sewing machine. If it’s not in a spot that’s easy to eyeball as you sew, put down a piece of masking tape or washi tape to mark it. Second, for perfect precision in the next steps, it’s really important that your stitching line goes all the way from end to end. I don’t even backstitch my stitches when I sew these, because the backstitch adds a bit of weight to the stitching line and I think throws off the measurement, and whatever cross seam you sew later with these blocks will lock these current stitches just fine. In my experience, the best way to get that perfect line of stitching all the way from end to end is to start sewing a couple of stitches before you push the fabric through, and then sew off the edge of the fabric by a couple of stitches when you finish the line. Hold the tails of both threads as you start to sew, so that the tension won’t suck them back into the stitching and make an ugly–and wide!–thread barf on the underside of your fabric.
Step 2: Cut the square into triangles.
To free those triangles, just cut precisely along the line that you marked from end to end. Now you’ve got two identical half-square triangles! They’re probably a bit wonky, though, and if they’re absolutely perfect they’re about 1/8″ too large, so let’s fix that in the next step.
Step 3: Iron and trim your brand-new half-square triangles.
Open up the half-square triangle blocks and iron them, being very, very careful to get the iron right up to the seam. I usually do this by finger-pressing the blocks first, then ironing them. Give each one a wee tug after you’ve ironed and if that opens up the block a little more, iron it better! Set the half-square triangle block onto a cutting mat that has a 45-degree angle marked across it, like in the above photo. Line up the line where the two triangles meet on that mark, then fiddle with it until you can see where you need to trim. For instance, I started with 2″ squares, and I want finished 1″ half-square triangle blocks, which means that I want this unfinished half-square triangle block to be exactly 1.5″ square to accommodate the quarter-inch seams I’ll be sewing. Ideally using a rotary cutting tool, trim the block exactly to size. You will have a total of 1/8″ wiggle room across each measurement, which will make up for a bit of wonky measuring and sewing. In the image above, for instance, notice that I skewed my block a little bit as I was sewing it, so trimming it lets me square it back up nicely. You can do so many cute things with your half-square triangle blocks! Here are some of the patterns that you can make: And when you add it full squares or other shapes, the possibilities become endless! Check out my patchwork monograms made with just squares and half-square triangles: I’ll show you what I’m going to do with those next week!
