We all long for sharp, flat seams in our quilts without lumps, bumps or flaps. There are a couple things you could do to improve the look of your seams.
Press your seams on the back first before opening them. The heat of your iron relaxes the threads in the fabric and sinks your sewing thread in a little bit. That way when you press your seams open, you won’t get the dreaded roll over.
Press – don’t iron your seams. When you iron (dragging your iron back and forth across your fabric), it’s very satisfying when you’re getting creases out of yardage. But that dragging motion can easily distort your seams – especially bias pieces. Even seams on the straight of grain can distort from that dragging. Pressing (putting your hot iron on the fabric, lifting it up and placing it in the next spot) will keep your seams nice and crisp.
Whether you’re a fan of pressing seams open or to one side when you’re working with high contrast fabrics press seams to the dark fabric side whenever possible. If not possible, press the seam open to prevent the darker fabric from shadowing through the light side.
If you get a twist in your seam when connecting blocks together (See the image to the left), clip the seam allowance far enough to free up the twist, press it again from the back and then when you press the front again it will lie flat.
Try a tailor’s clapper on bulky seams. A tailor’s clapper is a smooth piece of hardwood that you allows you to put pressure on a hot seam, setting the crease in a seam while it’s hot without the risk of leaving your iron on your fabric too long. Here’s a great article and tutorial on the benefit of a tailor’s clapper.