What's a 1/4" Seam Allowance?

That pesky 1/4" seam allowance.  It's the standard in quilting.  It's the key to making things fit together.  It's everywhere, but what does it actually mean in practice and how do you measure it?

Here's the most important thing I want to say about the 1/4" seam allowance.

It isn't the distance from the edge of the fabric to the line of stitching.  It's whatever gives the correct result.

Then why is it called a 1/4" allowance?  Because 1/4"  is the measurement we use for the quilt math we do to figure out how make parts fit together the way we want them to.  

Quilt math works with a perfectly 2-dimensional design, but fabric and thread exist in a 3-dimensional world. When you press a seam, the thickness of the thread and the thickness of the fabric itself result in the fold taking up a bit of the fabric.

In the 3-D world, what's left in the block is what you originally cut, minus 1/4" and that little bit lost in the fold.  You'll need to take that little bit into account for things to work out as planned in a pattern.

Read on for more questions and do's and don'ts of seam allowances.

How do I measure the seam allowance?

If you sew two 2" squares together, you should expect  a 2" x 3 1/2" unit (mathematically, each square loses 1/4" into the seam, so 2" - 1/4" + 2" - 1/4" = 3 1/2").

So, sew two  2" squares together with what looks like 1/4" seam allowance, press the seam to one side, and measure the unit.  

• If it's shorter than 3 1/2", your seam ate too much fabric.  Try again with a narrower seam allowance.

Seam allowance is too wide

• If it's longer than 3 1/2", your seam didn't eat enough fabric.  Try again with a slightly wider seam allowance

Seam allowance is too narrow

• If it measures 3 1/2", you've found the correct seam allowance.  You can mark the bed of your machine with tape or a stack of sticky notes as a guide to where to position the edge of the fabric to repeat that seam allowance, or take note of the needle position if you adjusted that to get the right seam allowance. 

Seam allowance is correct

You might be tempted to skip testing the seam allowance.  I get it.  Let's start building blocks already! Nevertheless, fudging might slow you down or mess you up later, and lead to more fudging to fix issues caused by earlier fudging, and so on, and so on.  I highly recommend taking the time now to save time later.

Can I just sew a "close enough" seam, as long as I'm consistent in all my seams?

Unfortunately, most of the time, this won't work out.  Sorry, it's a math and geometry thing.

For example, suppose a pattern includes this unit.

The pattern gives cut sizes that will make the two squares sewn together add up to a unit that is the same length as the rectangle it's being joined to, so they will fit together.  If the two squares add up to a shorter, or longer measurement, they just don't fit together, even if you use the same seam allowance on the horizontal seam.  The length will still be mismatched.  

Seam allowance too narrow

Seam allowance too wide

Can I just trim off any extra off the sides if parts don't quite match?

There are at least two possible problems with that approach.

Changing the dimension of a unit 

For example, in the unit I showed with a seam allowance that was too wide, trimming off the excess on the lower rectangle will make the unit measure 3 1/2" x 3 3/8" instead of 3 1/2" square.  It doesn't look like much of a change, but it's going to change how well it fits with other units in your pattern.  Over several units, it can really affect the total size in one or more directions, and possibly how square your project is.

Changing where seams fall in the unit

For example, in the unit I showed with the seam allowance that was too wide, shaving off some of the white is changing the proportion of the white piece.  When the green square and the white square were the same size, the seam was exactly in the center.  The white is now smaller than the green, and the seam is no longer in the exact center of the unit.

Depending on the design this might not be a big deal.  However, if the design needs that seam to line up in a particular way with some element in another unit, shifting that seam line away from the center might mess up the alignment.

Any other questions?

I think I've covered the basics. Do you have any other questions about seam allowance?  Add them in the comments or send me an email.  Now I'm off to sew the units for Week 2 of the Two-Colour Mystery.  After testing my seam allowance, of course.

Happy quilting,

Joanne

My thanks to Northcott Fabrics for the fabrics I used in this tutorial.

Sweet Trails: new pattern for spring

The weather outside my window has definitely bean leaning towards spring the last several weeks.  It's warmer than normal for this time of year, and a part of me worries it's just a cruel trick before cold rushes back in to destroy the buds the plants have gamely started showing.  The rest of me says I should just think positive and enjoy the sunshine and warmth.

Whatever happens to the buds outside, the cold won't damage these Sweet Trails blooms.

Sweet Trails by Canuck Quilter Designs
Fabric:  Heavy Metal, an Island Batik Signature Collection
designed by Kathy Engle for Swan Sheridan of Swan Amity Studios

You can see the block is based on a traditional snail's Trail block.

That gave me the nice swirling motion I was looking for, but it did present some challenges from a pattern-writing perspective.  Briefly, the snail's trail block has math that doesn't lend itself to making all the parts easy to cut with a rotary cutter.  For example,  2.267"  just isn't marked on the cutting ruler.  Neither is 3.328".  Rounding is an option, but then resulting units are also not quite a size that's easy to measure for trimming. And how tricky is it to trim evenly on all sides so the design doesn't end up lopsided?

What to do?  Make test blocks.  Lots of test blocks, with different permutations of rounding and trimming sizes and specialty tools versus no tools.

The Square on Square Trim tool from Creative Grids worked pretty well.  I'd use it again.  

That said I wanted folks without access to the tool to be able to make this design, so I kept trying versions without the tool.

What I came up with was a combination of rounding up to the nearest measurable size for initial cutting of parts, then trimming only on rounds where the desired size was a size that was easy to measure, like 4 1/2" square.  There are some points that get blunted just a smidge, but it really doesn't matter because the point isn't actually part of the design, it's just an accident of construction and blends right into the next piece in the same color, creating the swirl, even with a blunted tip.  The swirl is the important part!

It's all detailed in the pattern.  Just follow the instructions.  When I say "DO NOT TRIM rounds 1 and 3", don't trim round 1 and 3!  Rosie assures you it will all work out if you trust the directions.

I waffled about how to set these blocks and finally opted to make them float on the background, with a few starry leaf clusters to add a dash of contrasting color for pop.

I also chose to make the last border match the background to keep it visually light.  In combination, the thin inner border, the outside border and the binding act as a frame without being heavy.  I did list the border fabric amounts separately in the pattern so it would be easier to substitute another fabric if you wanted a more solid look.

Some of my test blocks made it onto the backing.

The rest of the test blocks, plus a few more I have pulled scraps for, will end up in a scrappy quilt.  I'm pondering alternate settings for that one, but I may circle back around to the original.  I won't get around to this for a while, so there's time for me to change the plan.

Have you ever made Snail's Trail blocks?  What method did you choose?  I probably should have asked this earlier! 

Now I'm off to work on Week 2 of the Mystery Quilt-Along.  The second clue will be emailed on Thursday, and I need to be a step ahead so I can share pics in my tips and tricks. 

Happy quilting,

Joanne

Get your copy of the Sweet Trails pattern as a PDF download in my Etsy shop or ask for a print version at your favourite quilt shop.

Look for the  Heavy Metal batik collection from Island Batik in stores now.

Strategies for keeping track of quilt piece counts when cutting fabric

How do you keep count of pieces when you're cutting?  I have different strategies when I'm cutting yardage than when I'm cutting scraps.

Fabric for Half and Half cut and ready to sew.
Thank you to Northcott for sending me these fabrics:
Dark is Stonehenge Gradations - Peacock - 26755-66
Light is Crackle - Snow - 9045-10

Counting when cutting yardage

Depending on how many layers I'm cutting at once, I count by twos or fours, and make stacks of 10 or 20, then add up my stacks for the total.

I cut the light fabric four layers at a time, so I counted by fours.  Each of the squares below is a cut with four layers,  so there are 20 squares there.  I fanned out the sets until I had 5 so I could count at a glance if got distracted and lost count.

20 light squares

Once I had 5 sets (20 squares) I stacked them to save space.

Still 20 light squares

I repeated this, making stacks of 20 squares, until I had the required number.  The I stacked the stacks, turning every stack a little so I could still count the individual stacks.  That will help me count more quickly later when I need only some of the squares for a particular step.

4 sets of 20 squares = 80 squares

By the time I started cutting my dark fabric I was feeling like cutting through four layers was hard work, so I cut the dark two layers at a time.  For two layers, I counted by twos and tens.

Each square has two layers, so there are a total of 10 squares

Still ten squares, but stacked

8 sets of 10 = 80 squares

I can't wait to start sewing these.  It's going to be so pretty!

Counting when cutting scraps

When I'm cutting scraps, I tend to cut different sized pieces at the same time, depending what I can get out of each scrap of fabric.  I had all different sizes of scraps to cut from when I made my scrappy test quilt for the mystery.

Red scraps for the scrappy version

Some could be cut in layers, but some needed to be cut one piece at a time. The methodical stacks I use when I cut yardage were not as useful, and I found myself losing count.  There really wasn't enough room on the cutting chart to tally the pieces as I cut, so I made up a different tally sheet.

All the dark parts for the scrappy version

It's not terribly clear in the photo, but I drew the different sized pieces on scrap paper, wrote in the label and the size, and had lots of room to add a tick mark in the appropriate piece for every piece I cut.  I grouped the ticks into groups of 5 (4 vertical ticks plus one across) for quick counting, and added a big checkmark when I reached the required total of any size, so I'd know not to cut any more that size.

It wasn't essential to draw the shapes. A list of sizes would have been sufficient, but I liked the drawn shapes as s visual aid to quickly locate the appropriate spot to add the ticks.  

Just in case you're wondering, the scrappy version of Half and Half turned out great. You can see it here. All those scraps add a lot of interest, and I managed to not overthink fabric placement too much.  I even ended up with the same fabric touching in places and didn't feel compelled to move them around.

Please share!

Please share your counting strategies with us in the comments. I'd love to know what works for you.  

Happy quilting,

Joanne