Half Square Triangles or HST: Part 1
What is it about Half-square triangles that make them so useful yet so frustrating? I have a few thoughts on that conundrum.
First of all, you can do so much with them. The traditional Churn Dash, Shoofly and so many other blocks utilize these versatile units. Second, a simple change in color placement can create secondary designs like pinwheels and squares on point.
However, frustration can arise when the bias edges get distorted or seams aren't sewn perfectly straight. If two triangles are sewn together to create a HST, then the pointed corners can get pulled down into our machine and cause a mess of tangled thread and wadded up fabric. If the seam isn't sewn perfectly, the HST may not end up the size needed.
So what can be done to ease or eliminate the frustration factor of this common unit? I have some suggestions. Some of these require special tools or supplies but most are doable with a simple square ruler at least as big as the unfinished size of the unit and a pencil.
To make a HST, the simplest way is to sew two triangles that are half of a square together along their long sides. The trick is knowing how big to cut the original square so that the finished size of the unit is correct. The answer is 7/8". So, for example, if the finished size desired for a HST is 3", the fabric used should be cut into squares that are 3-7/8". Each of the squares would then be cut in half along a diagonal from one corner to another. Here is where it can get tricky. The long sides of the resulting triangles are bias edges. That means they are going to be stretchy. It is very easy to distort the shape of these pieces.
Fortunately, there is a way to minimize the stretch. Use plenty of starch. Starch will stabilize the fabric and make both cutting and piecing easier and more accurate. Now, when I say starch, I don't just mean regular starch. I am using it as a generic term that would also include such products as Best Press. Whatever product you choose to use, read and follow the directions for best results.
Once you have your 2 triangles prepared, simply layer one on the other with right sides together. Sew them together using an accurate or scant 1/4" seam. Note that a scant seam means to sew inside the seam allowance by 1-3 threads. The thicker the fabric you are using, the further away from the exact 1/4" you should be. Be sure to sew straight without wobbling the seam.
[Aside: Scant seams are needed in order for the finished unit to be the desired size. The fold of the fabric takes up some space. Sewing a seam just slightly smaller allows for that fold. That is why thicker fabric would require that the seam be sewn further from 1/4".]
Once sewn, set the seam with your iron and then press it toward the darker fabric. Be sure to press on the right side to be sure that you haven't created a pleat. Your HST will have dogears that you can snip off with scissors or trim with your rotary cutter.
Check the size of your HST using a ruler with a 45 degree line. That marking should be lined up with the seam in your unit. Is the unit the correct size? I sure hope so. It will make the rest of your piecing easier and quicker.
If it isn't correct, is it too large? If so, trim it down keeping that seam line on the 45 degree marking. This also means that you have sewn too far from the exact 1/4" for the thickness of your fabric. Or is it too small because you sewed the seam too large? In this case, you may need to rip out the seam and try again or set this unit aside and make a new one.
Well, enough for this post. I'll be back with other methods to make HSTs soon.
First of all, you can do so much with them. The traditional Churn Dash, Shoofly and so many other blocks utilize these versatile units. Second, a simple change in color placement can create secondary designs like pinwheels and squares on point.
However, frustration can arise when the bias edges get distorted or seams aren't sewn perfectly straight. If two triangles are sewn together to create a HST, then the pointed corners can get pulled down into our machine and cause a mess of tangled thread and wadded up fabric. If the seam isn't sewn perfectly, the HST may not end up the size needed.
So what can be done to ease or eliminate the frustration factor of this common unit? I have some suggestions. Some of these require special tools or supplies but most are doable with a simple square ruler at least as big as the unfinished size of the unit and a pencil.
To make a HST, the simplest way is to sew two triangles that are half of a square together along their long sides. The trick is knowing how big to cut the original square so that the finished size of the unit is correct. The answer is 7/8". So, for example, if the finished size desired for a HST is 3", the fabric used should be cut into squares that are 3-7/8". Each of the squares would then be cut in half along a diagonal from one corner to another. Here is where it can get tricky. The long sides of the resulting triangles are bias edges. That means they are going to be stretchy. It is very easy to distort the shape of these pieces.
Fortunately, there is a way to minimize the stretch. Use plenty of starch. Starch will stabilize the fabric and make both cutting and piecing easier and more accurate. Now, when I say starch, I don't just mean regular starch. I am using it as a generic term that would also include such products as Best Press. Whatever product you choose to use, read and follow the directions for best results.
Once you have your 2 triangles prepared, simply layer one on the other with right sides together. Sew them together using an accurate or scant 1/4" seam. Note that a scant seam means to sew inside the seam allowance by 1-3 threads. The thicker the fabric you are using, the further away from the exact 1/4" you should be. Be sure to sew straight without wobbling the seam.
[Aside: Scant seams are needed in order for the finished unit to be the desired size. The fold of the fabric takes up some space. Sewing a seam just slightly smaller allows for that fold. That is why thicker fabric would require that the seam be sewn further from 1/4".]
Once sewn, set the seam with your iron and then press it toward the darker fabric. Be sure to press on the right side to be sure that you haven't created a pleat. Your HST will have dogears that you can snip off with scissors or trim with your rotary cutter.
Check the size of your HST using a ruler with a 45 degree line. That marking should be lined up with the seam in your unit. Is the unit the correct size? I sure hope so. It will make the rest of your piecing easier and quicker.
If it isn't correct, is it too large? If so, trim it down keeping that seam line on the 45 degree marking. This also means that you have sewn too far from the exact 1/4" for the thickness of your fabric. Or is it too small because you sewed the seam too large? In this case, you may need to rip out the seam and try again or set this unit aside and make a new one.
Well, enough for this post. I'll be back with other methods to make HSTs soon.
HSTs: Part 2
I'm back as promised to describe another way to make HSTs. The nice thing about this method is that you don't have to handle bias edges. An added bonus is that you get 2 identical HSTs. We will also make them slightly oversized and trim them down to the size we need. All in all, this method solves a number of the issues with sewing HSTs. So how does this work?
First, cut squares of your two fabrics 1" larger than the desired finished size. For example, to make HST of finished size 4-1/2", cut squares that measure 5-1/2" x 5-1/2". Next, on the back of one of the squares draw a diagonal line for one corner to another. Layer your two squares, right sides together, and stitch a 1/4" away from both sides of the line. Now, carefully cut along the drawn line separating the two HSTs. Set your seams and press toward the darker fabric.
The HSTs you've made will be slightly larger than our desired size - 5" in our example (4-1/2" + 1/2" for seam allowances). Using a ruler that is equal to or larger than our desired size and that has a 45 degree line marked, align the 45 degree line with your seam line. The HST should extend slightly past the 5" markings and the edges of the ruler. Trim two sides. Rotate the HST 180 degrees and align the 5" markings with the edges of the unit and the 45 degree line with the seam. Trim the remaining two sides.
Repeat the trimming on the second HST. That easily you have made two accurate HST units without handling any bias edges. There are many more ways to make HSTs so I'll be back with more.
First, cut squares of your two fabrics 1" larger than the desired finished size. For example, to make HST of finished size 4-1/2", cut squares that measure 5-1/2" x 5-1/2". Next, on the back of one of the squares draw a diagonal line for one corner to another. Layer your two squares, right sides together, and stitch a 1/4" away from both sides of the line. Now, carefully cut along the drawn line separating the two HSTs. Set your seams and press toward the darker fabric.
The HSTs you've made will be slightly larger than our desired size - 5" in our example (4-1/2" + 1/2" for seam allowances). Using a ruler that is equal to or larger than our desired size and that has a 45 degree line marked, align the 45 degree line with your seam line. The HST should extend slightly past the 5" markings and the edges of the ruler. Trim two sides. Rotate the HST 180 degrees and align the 5" markings with the edges of the unit and the 45 degree line with the seam. Trim the remaining two sides.
Repeat the trimming on the second HST. That easily you have made two accurate HST units without handling any bias edges. There are many more ways to make HSTs so I'll be back with more.
HSTs: Part 3
Sorry for the delay in posting the next part on HST units. Life has interfered with blogging.
So now for part 3 of half-square triangle units.
The method described in Part 2 can be extended to make multiple pairs of HST units from just 2 pieces of fabric. For example, let's say that we want to make 6 HST units that measure 3" finished or 3 pairs. That means we need 3 times the fabric as for 1 pair of HST. So figure the fabric for 1 pair. For 3" finished we would need squares that measure 4" = 3" finished + 1".
For 3 pairs, we would need 3 squares that measure 4" x 4". If we cut them as 1 piece of fabric, we will need rectangles of each fabric that measure 12" x 4" or (3 times 4") x 4". To sew the HST units, we need to draw some lines on the back of one of the rectangles. First, mark lines to split the fabric into three 4" x 4" squares. Now draw diagonals across each square. The trick to make the sewing easiest is to draw the lines so that you can simply turn the fabric to continue sewing along the diagonals rather than having to cut the thread.
Lay the rectangles so that the 12" side goes from side to side. The lines that split it into 4" x 4" squares will be vertical. Now draw the diagonals starting at the top left corner to the bottom right corner of the square on the left and the one on the right. In the middle square, draw the diagonal from bottom left to top right. The diagonals will form a zig-zag path across the rectangle. Start sewing at a corner, turn at each edge to follow the zig-zag. At the end of the zig-zag, turn and follow the zig-zag back along the path along the other side of the lines.
To separate your 6 HST units, carefully cut along ALL of the drawn lines. Then simply press and trim as has been described in Parts 1 and 2.
This method allows you to handle larger pieces of fabric and saves sewing time. The time to press and trim is essentially the same.
Now this isn't the end of methods for sewing HSTs. More will follow soon.
So now for part 3 of half-square triangle units.
The method described in Part 2 can be extended to make multiple pairs of HST units from just 2 pieces of fabric. For example, let's say that we want to make 6 HST units that measure 3" finished or 3 pairs. That means we need 3 times the fabric as for 1 pair of HST. So figure the fabric for 1 pair. For 3" finished we would need squares that measure 4" = 3" finished + 1".
For 3 pairs, we would need 3 squares that measure 4" x 4". If we cut them as 1 piece of fabric, we will need rectangles of each fabric that measure 12" x 4" or (3 times 4") x 4". To sew the HST units, we need to draw some lines on the back of one of the rectangles. First, mark lines to split the fabric into three 4" x 4" squares. Now draw diagonals across each square. The trick to make the sewing easiest is to draw the lines so that you can simply turn the fabric to continue sewing along the diagonals rather than having to cut the thread.
Lay the rectangles so that the 12" side goes from side to side. The lines that split it into 4" x 4" squares will be vertical. Now draw the diagonals starting at the top left corner to the bottom right corner of the square on the left and the one on the right. In the middle square, draw the diagonal from bottom left to top right. The diagonals will form a zig-zag path across the rectangle. Start sewing at a corner, turn at each edge to follow the zig-zag. At the end of the zig-zag, turn and follow the zig-zag back along the path along the other side of the lines.
To separate your 6 HST units, carefully cut along ALL of the drawn lines. Then simply press and trim as has been described in Parts 1 and 2.
This method allows you to handle larger pieces of fabric and saves sewing time. The time to press and trim is essentially the same.
Now this isn't the end of methods for sewing HSTs. More will follow soon.
