Quilting 101: Achieving Flat Seams | Madam Sew

How to Get Flat Seams: The Art and Science

Flat quilt seams are more than an aesthetic pursuit… They are the mark of an exceptional quilter! And, those perfectly flat seams aren’t achieved by chance. There is both an art and a science to it.

Now, I’m not saying that your quilts must be perfect, but learning how to achieve flat seams will help the quilting process go smoother and will result in better looking quilts. That’s why I’m sharing five tips with you today to help you improve your quilting skills and achieve those coveted flat quilt seams.

Quilts Made by Carole Carter

Tip #1: Press Quilt Seams with Starch

Starch is a chemical used to stiffen fabrics and make them feel crisp. It has been used for centuries to stiffen cuffs, collars, and other clothing items. Starch can be applied to various types of fabrics, and quilters often use it on cotton fabric to make it stiff and easier to manage.

Quilting cotton that has been starched feels more rigid and is less prone to fraying. It also retains creases and stays smoother than non-starched fabric when ironed. So, if you have some quilt seams that keep popping up after you iron them, some spray starch can help give your fabric the rigidity it needs to stay flat.

Many quilters have incorporated starch into their regular quilt preparation routine—they prewash their quilting fabric to preshrink it and then soak it in a starch solution before letting it dry. This creates crisp fabric that is easy to cut and piece, with minimal risk of shrinking in the future. However, there is quite a bit of debate in the quilting world about whether prewashing quilt fabric is necessary or not. I’ll let you make that choice, but you may want to check out my recent post about it: The Prewashing Debate for Quilting Fabric.

Crisp, Starched Quilt Fabric

In addition to soaking quilting fabric in starch, many quilters also keep a bottle of spray starch near their pressing station to spray additional starch on difficult seams. Mary Ellen’s Best Press is one of the most popular brands of spray starch, but there are others and you can easily make your own DIY starch, too.

Best Press Spray Starch

There are a couple of drawbacks to using starch… It can leave residue on your iron or pressing surface, your fabric doesn’t feel as soft, and some people are allergic to it. Luckily, it is easily removed when you wash your finished quilt. However, fabric starch can also burn if your iron is too high! See the image below with a mild case of burnt starch on the block.

Quilt Block with Burnt Fabric Starch

Tip #2: Use a Wool Pressing Mat

If you’re not a fan of fabric starch, a wool pressing mat is a great alternative. Wool has some amazing properties! It absorbs and retains heat from your iron. So, when you press a seam on a wool pressing mat, heat is applied from both the top and the bottom. This results in super-flat quilt seams. That’s why wool pressing mats have gained popularity so quickly amongst quilters.

When you use a wool pressing mat, there’s no need to use steam or starch. Plus, the soft surface prevents the seams from making noticeable creases on the front of your block! The image below shows a quilt block that was pressed on a regular ironing board with minimal batting. Notice how you can see where the seam allowance is through the block because a small crease has been created. This could have been prevented with a wool pressing mat.

Quilt Block with Noticeable Crease on the Front

If you don’t have a wool pressing mat yet, Madam Sew sells a nice, large wool pressing mat that is 17”x24”. They also have a smaller wool pressing mat that is perfect for creating a small pressing station or for taking to quilting retreats. It really will help your quilt seams to lay flat and look better.

Wool Pressing Mat

Tip #3: Set Seams with a Quilter’s Clapper

Another thing you can try if you’re having difficulty getting your quilt seams to stay flat is a quilter’s clapper. It’s basically a polished piece of wood that you place on top of your quilt blocks after pressing them. It keeps the seams flat as they cool, with the added benefit of absorbing moisture that can cause your seams to curl as they dry from the steam of your iron.

Some quilters love clappers; others hate the extra space they take in their already crowded pressing station. Do you use a quilter’s clapper? Let us know in the comments below, and maybe it’s something Madam Sew can develop and add to their shop.

Flat Quilt Seams

Tip #4: Pay Attention to the Direction You Press Seams

As you piece your quilt top together, you’ll need to decide which way to press your seams. Sometimes you’ll press them to one side and other times you’ll press them open. The direction you press your seams makes a difference in how flat your quilt blocks can get. Bulky intersections in seams are the biggest culprit for quilt blocks that refuse to stay flat.

The following image shows two half-square triangles that are pieced together. The seam is bulky where all of the points meet and the seam doesn’t lay very flat. As you can imagine, when you have a ton of half-square triangles pieced together, it can be a real challenge to get them to stay flat. See how the quilt seam below has popped up at the edges?

Quilt Seam Popped Up

If you are using a quilt pattern, it typically tells you which way to press your seams. If you’re not using a pattern, you’ll have to think carefully about the best way to press your quilt seams to reduce bulk so that your blocks can be as flat as possible. You may have heard quilters say that you should always press your quilt seams towards the darker-color fabric. This is good advice in general, but sometimes you’ll want to go against this rule to reduce bulky seams.

Tip #5: Use 50wt Cotton Thread

One mistake that a lot of people make when they are new to quilting is that they piece blocks together with regular, all-purpose thread. This does work, but you’ll get flatter quilt seams if you use a 50wt cotton thread instead. Regular thread adds bulk to the seams and prevents them from laying flat when pressed. It messes with your perfect ¼” seams, too, because one side of your block might be slightly higher on the side that you pressed the seam allowance. It’s hard to tell in the image below, but if you look closely at the seam, you’ll see a small hump/roll on the right side where the seam allowance has been pressed to that side. This could have been minimized by using thin, 50wt cotton thread.

Uneven Quilt Block When Pressed

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Once you start using 50wt thread for piecing, you’ll never use anything else. The difference in thickness is more noticeable than you might expect. 50wt quilting thread has become a favorite for quilters because it is specially made to be ultra thin, but still strong enough that it won’t easily break. Plus, it is lint resistant and doesn’t build up in your machine as quickly as other thread varieties.

Flat Quilt Seams

I hope you will try some of the tips in this post. Let me know if they help you get flatter quilt seams. Do you have any other tips to add? Let me know in the comments below.


Cara Stromness,
Blogging for Madam Sew and Sewing Society

Cara loves sewing, quilting, and machine embroidery. Be sure to check out her sewing projects!

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1 comment

Very nice information and pictures definitely a plus. Well done!

Leila Farley

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