Equilateral Triangles
An equilateral triangle, or a regular triangle, has three sides of equal length and three equal interior angles of 60°.

When I think of equilateral triangles in quilts, I think of Thousand Pyramids.  As I was doing a little research into this quilt design, I realized that it isn’t limited to equilateral triangles – any isosceles triangle will do.  That is to say, it requires two sides of equal length, not necessarily three.  Nevertheless, let’s take a look at Thousand Pyramids and some of its variations.

In this first example, equilateral triangles are sewn together into rows.  The second and alternating rows are mirror images of the first row.  The upward pointing triangles are one color and the downward pointing triangles another.

Another option is to color opposite triangles in such a way as to form diamonds.  This version is sometimes called Tumblers, although tumblers can also be a different shape altogether.

By off-setting the rows of triangles, Thousand Pyramids becomes Lightning.  In this coloration, with the dark triangles pointing down and the light triangles pointing up, a Dog’s Tooth design is created.

But by coloring the upward-pointing and downward-pointing triangles as a row, you get the Streak of Lightning effect.

Scalene Triangles
A scalene triangle has three unequal sides.  The interior angles may vary, but for quilters one of them is usually 90°.

This block is called Double Z and it has both scalene and isosceles triangles.  The light and dark violet patches are the scalene triangles.

Often, scalene triangle patches are found in blocks where a rectangular patch is divided in half diagonally.  Such is the case in this Nosegay block.

This example is just full of scalene triangles.  The block is called Cool Fan – just what we need in this summer heat!

Acute and Obtuse Triangles
These triangles are identified by their interior angles.  An acute triangle has three interior angles that are less than 90° whereas an obtuse triangle has one interior angle which is greater than 90°.

Many of the scalene triangles in the examples above are also acute triangles.  Patchwork blocks with obtuse triangles tend to also have acute triangles – which makes sense when you think about it.  In The Priscilla block, obtuse triangles fill in the space formed by the acute triangles.

I really like the look of this block set on point.

One of the first quilts that I ever made – the first quilt, I believe, that I finished – was made from a block of squares and half-square triangles.  The quilt, called Cabin Lights, was pictured on the cover of the first issue of Quiltmaker magazine that I ever bought (which must have been sometime in 1994).  The design is created by the position of light and dark color values.  It was presented in the magazine as a scrap quilt but since I didn’t have any scraps yet, I had to buy all the light and dark blue fabrics that I used in the quilt.  I called my quilt “Miles To Go Before I Sleep”, because the wintry trees in the border fabric reminded me of Robert Frost’s poem Stopping by Woods on a Snowy Evening.

There are so many blocks made entirely from half-square triangles, it is hard to decide which ones to feature.  So let’s choose from some of the quilts I have made.  This first block is an old classic called “Corn and Beans”.  Where the four blocks came together in the middle, I replaced some of the smaller triangles with a large one to create space for the appliqué.  A pieced border echoes the shapes formed by the blocks.  The result is a 24-½” square wall quilt called Great is Thy Faithfulness.

Another block made entirely from half-square triangles – with a name near and dear to my heart – is Lady of the Lake.  Again, I modified the block by replacing some of the small triangles so that four blocks together would have open background space.  In this space, I appliquéd cottage-themed sewflakes – papercut appliqué designs.

I discovered something interesting while I was designing this quilt.  When two sets of half-square triangles came together along the outer edges of the Lady of the Lake blocks, they formed a flying geese unit.  This is how I ultimately constructed the quilt, also adding a border of half-square triangles to complete the flying geese around the outside edges.

The entire quilt measures 64″ square and is called Be Still.

This final example was chosen because it illustrates a less traditional use of half-square triangles.  The blocks were made using Paula Nadelstern’s simple symmetry technique.  Four half-square triangles were cut from the exact same location in symmetrical fabric as well as four mirror-images of those triangles.  When the eight triangles were sewn together, beautiful kaleidoscopic images were formed.  In this case, the triangles are just the tool that was used to create shapes that are anything but geometric.  I’d say, based on our categories of shapes, the kaleidoscopic images are non-objective or maybe even accidental.

Believe it or not, I have more to say about triangles!  This is because half-square triangles, while predominant, are not the only kind of triangles used in quilts.  Next week, we’ll look at equilateral, scalene, acute and obtuse triangles to discover what amazing effects they can produce in quilt design.