Hey Everyone, welcome back to Technique Tuesday. Last week I talked about how to make half square triangles using the traditional method with 2 squares. This week I am going to make half square triangles with a grid method – this method works great if there are many half square triangles needed of the same two colours.
Two nicely pressed fabrics are needed to make the half square triangles. I have chose to make mine out of a dark pink and a medium pink – these fabrics will have good contrast when put together.
How large are the half square triangles to be? For this example I have made them 3″ finished and 3½ unfinished. We will be working with the unfinished number to create the grid. Twelve half square triangles are needed which means we need to make a grid of 6 as each square in the grid will create two half square triangles. The grid will need to be 3 squares across and 2 up and down.
Grids can be as small as 2 x 2 or as large as the piece of fabric you wish to work with.
How big does the fabric need to be cut for the grid?
I add an inch onto the unfinished size and then multiply by the number across and the number up and down to determine how big to cut the fabric. I use an inch instead of ¾″ only because it is much easier to do the math – there is a bit more fabric wastage but for easy math it is worth it.
For example: The HSTs are 3½″ unfinished – add an extra inch to the unfinished size to make 4½″. There are 3 across in the grid – 3 x 4½ = 13½. The width of squares is 2 – 4½ x 2 = 9. The pieces of fabric to make the grid needs to be cut 9″ x 13½″.
Preparing the Grid
1. Lay out the two fabric pieces right sides together matching up the edges evenly.
2. With a pencil or fabric marking pen and ruler draw a line down the centre of the fabric lengthwise at the 4½″ mark.
3. Mark off intervals lengthwise of 4½″. Draw lines vertically on the fabric at the 4½″ mark and 9″ mark.
4. Draw a diagonal line from the top left corner to the bottom of the second vertical line continuing the line up to the corner of the centre line.
5. Draw a diagonal line from the bottom left corner to the top of the second vertical line continuing the line down to the corner of the centre line.
6. Pin the grid together – this will prevent any movement when sewing.
Sewing the Grid
1. Start sewing at one of the corners on one side of the diagonal pencil line and follow along in a continuous line. This will be a ¼″ seam – line up the edge of the quarter inch foot on the line to ensure a ¼″ seam.
2. At the edge lift the foot and pivot around to start back down along the pencil line. If you wish to stop and cut threads that is fine but really no need.
3. Completed sewing line is a ¼″ from the pencil line all the way around..
4. Sew another ¼″ seam on the other side of the line – lining up the edge of the quarter inch foot with the pencil line will make it easier.
5. At the corners, stop and leave the needle in the line, lift foot and pivot the fabric around lining up the edge of the foot with the line, continue sewing a ¼″ seam.
6. Sewing lines complete on either side of the diagonal pencil lines.
Cutting the Grid
1. Cut apart along the horizontal pencil line in the centre of the grid to make 2 long pieces.
2. Cut apart along the vertical pencil lines to make 6 squares.
3. Cut along the pencil lines between the sewing lines to make 12 half square triangles.
4. Press all the half square triangles open towards the dark fabric.
Squaring Off the HST
Squaring off is when the HST is trimmed down to the size needed.
1. Place the HST right side facing up and the seam line going from bottom left corner to top right corner on the cutting mat.
2. I use a small square ruler such as 4½″, 5½″ or 6½″ square for squaring off as these small square rulers are much easier to work with than the regular 6½″ x 24″ ruler for this job. The HST needs to be squared off to 3½″.
Line up the diagonal line of the ruler at the left hand bottom corner of the seam line with the 3¾″ vertical and horizontal lines matching the side and bottom edges of the HST as best you can. It is very important that the diagonal line on the ruler is square on with the diagonal sewing line of the HST. See photo below.
3. Trim off the excess fabric on the right hand side and top of the ruler.
4. Spin the HST around so that the edge just cut is at bottom left hand corner.
5. Repeat step 2 only this time placing the 3½″ vertical and horizontal ruler lines on the side and bottom edge of the HST. Take care to make sure the diagonal like is once again lined up with the seam line.
6. Trim off the excess fabric on the right hand side and top of the ruler.
7. The HST is squared to 3½″.
So there you have another method of how to make half square triangles. This one is certainly very handy if a lot of the same two colours are needed. There are also commercially stamped grids that can be bought to accomplish the same thing – I have never used them as I find drawing the lines on the fabric works just fine.
If you have any questions or are having difficulties please feel free to contact me, I am happy to help and only an e-mail away.