How to make disappearing half square triangles quilt blocks

DISAPPEARING TRIANGLES

I think disappearing half square triangles is one of my favorite cut up quilt blocks to make. It starts out so easy and ends up looking so intricate. These finished blocks make beautiful quilts and table toppers. If you’re a bit nervous about cutting up your good fabric, try this technique with scraps or even colored papers. Scrapbooking paper works nice. To start with, you’ll need fabric in two contrasting colors. Make sure they are highly contrasting or this doesn’t look as good once the blocks are finished.

For each block, you’ll need two squares each of two colors, all the same size. I used 4 inch blocks for this sample. You don’t want to go much smaller than that or your final cuts will be really small.

How to make disappearing half square triangles quilt blocks

How to make disappearing half square triangles quilt blocks
How to make disappearing half square triangles quilt blocks

Draw a diagonal line on the back of the lighter colored squares (or whichever ones you can see your marking on easier). I show a really bold line here, but you don’t want yours so visible. Sandwich the pieces, right sides together.


Along each side of the diagonal lines you drew, sew a seam 1/4 inch from the line, on each side of the line. Then carefully cut along the line drawn, and press squares open. You’ll have 4 triangle squares all the same.

How to make disappearing half square triangles quilt blocks
How to make disappearing half square triangles quilt blocks
How to make disappearing half square triangles quilt blocks

Next, rotate the squares so two darker triangles are facing each other in the center and the other two are facing away from the center, like I show here. 

How to make disappearing half square triangles quilt blocks

How to make disappearing half square triangles quilt blocks
How to make disappearing half square triangles quilt blocks

Sew these squares together in pairs, making sure you line up your seams nicely. Then sew the pairs together to form a block. Again be sure your seams line up, especially in the center. 


If you have a cutting surface with a grid, this makes this next step really easy. Line up the center seams vertically and horizontally with lines on your grid. (See the little red arrows.) Measure evenly from each edge (all four) and trim the block equally on all four sides.  (If you don’t have a grid to work on, you’ll need to measure very carefully from the center in all four directions and trim equally all the way around.) Once the excess is all trimmed off, you are ready to make your final cuts. My trimmed block is 6-1/2 inches square.

How to make disappearing half square triangles quilt blocks
How to make disappearing half square triangles quilt blocks
How to make disappearing half square triangles quilt blocks

Now you’ll cut your block in thirds, the same cuts both vertically and horizonally. If your block ended up equally divisible by three, like a 6 or 9 inch block, you make your cuts evenly. If your block is not evenly divided by three, make your outer pieces slightly bigger than the center pieces. My block ended up to be 6-1/2 inches square, so I cut 2-1/4 inches in from each side, leaving the center pieces 2 inches wide.

How to make disappearing half square triangles quilt blocks

How to make disappearing half square triangles quilt blocks
How to make disappearing half square triangles quilt blocks

Next, take the four corner squares and rotate each so the small triangle in their corner is pointing outward instead of toward the center. Give the center square a quarter turn. Push the pieces back together and see what a cute block this simple move makes.


Sew these pieces together in three strips, taking care to keep them in the right order and the right direction. Make sure your seams all line up. It helps to pin or clip them so you don’t sew the wrong sides together. It’s easy to get them mixed up. (Believe me, I talk from experience here. Let’s just say I’ve become good friends with my seam ripper and leave it at that.) Sew the three strips together, watching your seam alignment again, and you have a finished block!

How to make disappearing half square triangles quilt blocks
How to make disappearing half square triangles quilt blocks

Now it gets fun! Make several of these blocks. Play around with putting them together in sets of 4 to form a larger block. Here are two of my favorite configurations, but there are more you could do. You could make a whole quilt with either of these, or alternate the two designs, or you could alternate them with the basic triangle block we started with. Add sashing or borders as you like. The possibilities are pretty endless.

How to make disappearing half square triangles quilt blocks
How to make disappearing half square triangles quilt blocks
How to make disappearing half square triangles quilt blocks

I hope you enjoyed learning this technique, and next time I’ll show you a similar one using simple strips of fabric. Happy sewing!

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