# Welcome to Back Quilt Lab –

# Half-Square-Triangles Edition!

**The Premise:**

I have a new quilt pattern in the works that uses somewhere around 1,500 – 1 ½” Half-Square-Triangle Blocks (aka HSTs). Yes, that’s a ton of tiny blocks … and thinking about it made me wonder: what is the fastest, most accurate and cost-effective way to make these blocks with as little waste as possible? And with that, the idea of Quilt Lab was born!

For this month’s segment, we’re going to explore the myriad ways to make HSTs, the math behind each method, the time it would take to make 1,500 units, and the extra cost and/or fabric waste with each method. While we won’t cover *each and every single *method for making this fun little blocks, I think we’ll hit the majority of the main categories.

**This Week:**

Two weeks ago, we explored the basics of making HST blocks using two single triangles. We’ll have three posts this week, each addressing a different way to make multiple HSTs at once. Last week talked about 2 HSTs at once and today we’re talking about the 4 HSTs at once method, also know as the *Missouri Star Quilt Co* method.

We are not taking into account the time it takes to cut yardage into strips, since everyone has different methods and speeds for strip cutting, and some people are using scraps – there are just too many variables to include this in our calculations. **Please note:** There are no affiliate links in this post – we have purchased all the tools used in our Quilt Lab experiments and are providing our honest, unaltered opinions. 🙂

**HSTs – Four at a Time**

Missouri Star Quilt Co has a fantastic YouTube channel and put together a great tutorial for this method for making four HSTs from two squares.

#### The Math:

The actual math for this method is a little bit yucky, but using the good ‘ole Pythagorean theorum, each square needs to be the size of you *un-finished* HST block ÷ 0.7071, plus 3/8ths of an inch for a seam allowance. Round this number up to the nearest 1/8th inch and this is the size of your starting square.

**2″ ÷ .7071 = 2.8285″**

**2.8285″ + .375″ = 3.2035″**

**Round up to 3 ¼”**

#### The Method:

Place two squares right sides together, pin in place, and sew around the entire perimeter. Then, cut the unit in quarters, diagonally, and press seams as desired.

#### The Time: 1’01.25″ per Block, as follows:

**Cutting Time, Part 1:**0’28” to cut a square from each print = 0’07” per block**Sewing Time:**0’41” to sew four seams = 0’10.25″ per block**Cutting Time, Part 2:**0’20” to cut unit into quarters = 0’05” per block**Pressing Time:**0’14” per block**Trimming Time:**0’12” per block**Additional Trimming Time:**0’13’ per block

#### The Report Card:

Using this method, **making 1,500 HST blocks would take approximately 25 hours and 25 minutes**.

**An Important Factor:** Even though my numbers were mathematically correct, my block turned out to be slightly too small. I repeated the experiment, rounding my measurement up an additional .25″ … but then had to trim down the blocks to the correct size … hence the *additional trimming time*.

**The Cost: **No additional cost

**The Waste:** Negligible – trimmed dog ears and possible a bit of scrap left over at the end of each strip

**The Pros:**

- If you don’t need a specifically sized finished block, then this is a great method for easily using charm, layer cake, or other scrap squares.

**The Cons:**

- The blocks now have bias edges, rather than straight-grain edges. Bias edges are notoriously stretchy and distort easily … this might not cause problems when using just a few blocks, but would be very problematic for an entire quilt top made solely from these blocks.
- The math is icky – if you need a specific size for your project then your blocks will almost always have to be made larger and then trimmed down to size.

So, to sum up what we’ve found out so far:

- Two Triangles + EZ Angle Ruler = 17 hours 55 minutes
- Two at a Time + A Guide = 25 hours
- Four at at Time: 25 hours 25 minutes
- Two at at Time = 27 Hours 5 minutes
- Two Triangles = 31 hours 40 minutes

The EZ Angle Ruler method is still in first place – we’ll see tomorrow how the 8-at-a-time method measures up. See you then!

JoyceLM says

I like this method of making 4 HSTs from 2 squares. But the math I use is from the following site. I divide the unfinished size of my HSTs by .64, and round it up a bit. I square them up, but I would always square up my HSTs no matter how I made them.

http://whipup.net/2011/03/17/guest-blogger-series-half-square-triangles/

Shelley @ CQ says

Thanks Joyce! The 64% calculation does work, but it’s not quite as precise as the longer formula we shared. For our purposes, this formula would tell you that you need 3.125″ squares to make the 4-at-a-time HST blocks at 2″ unfinished, but you would actually need at least 3.25″ squares, if not 3.375″ to get an accurately sized block.

As long as you give yourself an extra 1/4″ or 1/2″ using this calculation to give yourself some room to trim down, you’d be just fine. Thanks for stopping by and sharing! 🙂