Press, Don't Iron
Seam's sewn. Two squares are joined the way they're supposed to be. Before you add anything else to that unit, press it.
Press it. Don't iron it. That's not fussiness about words. It's a different motion and it matters.
Why this is its own lesson
Ironing is for shirts. You slide the iron back and forth, work out wrinkles, drag it around. Fine for a shirt. A shirt isn't held together by a quarter-inch seam that's still finding its shape.
Pieced fabric is different. Your squares are cut on grain, or close. That seam is brand new. Shove an iron across it like you're ironing a sleeve and you stretch the fabric right along the seam line. It goes soft and wavy instead of flat and square. Stretch it off-grain and you can't un-stretch it. You're stuck with it.
I learned this the hard way. It ties into my first quilting mistake: cutting my squares off-grain. First block I pieced, I didn't know grain was a thing. Nobody told me and I hadn't thought to ask. I cut my squares every which way, sewed them together, and the whole block came out bowed like a potato chip. Wouldn't lay flat no matter what.
So I ironed the heck out of it. Slid the iron back and forth maybe forty times, figuring harder or longer would flatten it. It didn't. All that ironing stretched the seams more and made the bowing worse. I finally admitted the block was cooked and started over.
Two lessons from one mistake. Cut on grain. And when you press, press, don't drag.
How to actually do it
- Set the seam first. Before you open the squares apart, lay the unit down with the seam still closed, exactly how you sewed it, and press it flat like that for a few seconds. This is "setting the seam." It lets the stitches settle into the fabric before you start folding things around. Skip it if you want. I don't.
- Open it up and press the seam to one side. With hand piecing you almost always press seams to one side rather than open, usually toward the darker fabric so it doesn't shadow through the lighter one. Fold the top square back so the seam allowance lays flat underneath.
- Lift the iron. Set it down. Lift it again. That's the whole motion. Down, hold a couple seconds, up, move it over, down again. You're not sliding it across the fabric like you're smoothing frosting on a cake. You're stamping it.
- Let it cool before you handle it. Fabric holds heat a minute, especially with the dry air we get around here. It feels dry to the touch fast, but the fibers are still warm and a little more willing to stretch. Give it a second before you pick it up and start working with it.
A dry iron is fine. Some people like steam because it presses crisper, but steam plus a shove is exactly how you get the stretching. If you use steam, be even more careful to lift and set instead of dragging. Your call. I'd nail the lift-and-set motion dry first and add steam once that's automatic.
One thing to watch for
Seam allowance showing on the front, poking out past the fold? You pressed it wrong, or toward the wrong side. Open it back up, refold it, press again. Don't iron over the mistake and hope it disappears under pressure. Heat doesn't fix a fold that's in the wrong place.
Also, the iron is hot enough to burn you. Keep it upright on its heel when you're not actively pressing. Keep little hands away from the cord and the base if you've got kids around the table. I don't hover much in this class, but that one I'll say plainly once and then trust you.
Before next time
Press the seam on the block you sewed last lesson, using the lift-and-set motion, and look at whether it's laying flat and square. If it's bowing at all, that's useful information for the next step, not a failure. Just tell me what you're seeing when we're back together.