Modern Quilt Blocks: Half Square Triangles

JUL 17, 2014

Back in May, quilter and blogger Michelle Wilkie visited the Spoonflower Greenhouse to teach folks how to make unique modern quilt blocks. For those of you who couldn't be here with us, follow Michelle's tutorial below to learn how to sew half square triangle blocks. 

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For our North Carolina friends, we'll be hosting the second in Michelle's modern blocks class series where she'll be teaching more of her original patterns to make blocks that can stand alone, or to incorporate into a sampler quilt, coming up July 27th. Join us

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Planning your block  

First, plan out your fabric and color choices.  You will need to think about four colors (try not to use directional prints). Download this diagram of the block to map out your color choices. This is your plan for the block.

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Cutting instructions for the block

Color 1 (Green above): 3 4.5” square and 3 3.5” square

Color 2 (Blue above): 3 4.5” square and 3.5” square

Color 3 (Orange above): 4 4.5” square and 4 3.5” square

Color 4 (White above): 2 4.5” square and 2 3.5” square

Final Block size is 12”

There three basic ways of sewing up half square triangles (HST). You can cut two triangles to size and sew a ¼ inch seam. This can be tedious if you need a lot of HST.

For this block we have six HST per row. Lets focus on the fabrics you planned and cut for that first row. In my block, that is the green and blue fabrics. We will use the two remaining time saving methods to cut and sew the HST for that first row.  

Method 1
Take one of the blue and green 4.5” squares.  Lay them on top of each with the right sides facing. Make sure you have all the corners lining up. Sew a ¼” seam around the square.

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Using a ruler line up a diagonal corner-to-corner. Cut. Repeat with the other diagonal as well. You will now have four pieces. 

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Press the seams open on all four HST. Trim the blocks down to 2.5” making sure the diagonal line of where the fabrics meet remains in the corners.

Note: I like to trim my blocks down for accuracy, so I do make them slightly larger. The equation I use is for what size squares I need is as follows:

final block size + (final block size 0.625) + 0.5” 

In my case this equates to: 
2.5 + (2.5 x 0.625) +0.5” = 4.5”

Method 2

Now, we need two more HST. Take one blue and green 3.5” square and lay them on top of each with the right sides facing. Make sure you have all the corners lining up.

This time you need a marker pen and your ruler, as you need to draw a line across the diagonal on one of the wrong sides. Once the line is drawn, you will need to sew a ¼” seam on either side of that drawn line.

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Once completed, cut along the drawn line using a ruler. You will now have two HSTs.

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Press the seams open on both the HST. Trim the blocks down to 2.5” making sure the diagonal line of where the fabrics meet remains in the corners.

Note: The equation I used to get the final HST is:

Final block size + 1” = 2.5+1 = 3.5 (others may use 2.5 + 7/8)

Continue with the other pieces until you have all 36 HST ready.

Completing the block

It is important to lay out your block on a design wall or planning space so that you know what you are sewing. Once you have done this you are ready to sew each row together. You will finish with six strings of HST (each consisting of 6 HSTs). All my seams are ¼”.

Pressing your seams is important. Folks typically either press to one side or press their seams open. Here’s what to consider when pressing your seams of these rows.

Pressing Seams to One Side

Benefits

Much easier to line up each row seam producing nice lines in the block

Cons

Seams tend to be bulkier which may cause difficulty when quilting

For this pattern, since the HST go in different directions, only half of the triangle intersecting points can be seen (see image below)

I use the ¼” intersection points of the two seams and the line in the HST to help get perfect points (noted by the arrows). The circle in the image below represents where you cannot use the HST line for seam guidance. You can see that here:

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Pressing Seams Open

Benefits:

Lays flatter, removes the bulk and makes it easier to quilt

All intersecting 1/4" seams and the line of the HSTs are visible as you sew (see image below)

Cons:

You can still match up the seams, but more pinning is required to ensure less fabric movement

By pressing seams open on the rows, I can use the line of the HST and the ¼” seams to ensure those perfect points on my HSTs (noted by arrows in the images below).

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Press your seams in your preferred method, sew all rows together and your block is complete! 

We hope you enjoy making some modern blocks with Michelle's half square triangle tutorial. Please share photos of your finished blocks with us and the Spoonflower community here! If you have any questions, please post them in the comments section below! 

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