When preparing fabric to make a quilt, the first step is to prewash your fabric to remove any chemicals and lose dyes. The second step is to starch, press, then square the fabric so you're cutting accurately and on grain.
5 Steps to Starching Fabric for Quilting:
1. Always press with a very firm pressing board - The pressing surface you use is actually very important. Regular ironing boards are simply too soft and will not properly press the starch with your fabrics. Click Here to learn how to build a super firm pressing board.
2. Clip all threads - After prewashing and drying your fabric, you may have loose threads on your fabric that will catch and pull your fabric out of shape. Clip these off so they don't get in your way.
3. Spray starch over the front side of the fabric - Spraying over the front will help to bond the starch into the fabric fibers.
4. Flip the fabric over - It's very easy to singe fabric when you press a hot iron to fabric wet with starch. Flipping it will completely eliminate this problem.
5. Press from the back with a hot dry iron - Your goal is to completely bond the starch with your fabric. Pressing from the wrong side of the fabric will force the starch to bond with the fabric and reduce the chance that it will flake off against your hot iron.
By pressing from the back on a very firm pressing surface, you reduce the chances of singed fabric and increase the amount of starch actually bonding with the fabric fibers.
How to square your fabric before cutting
The next step is to square your fabric so the grainline - the lines of threads that run vertical and horizontal through your fabric - is aligned square and straight so you can cut shapes properly.
Importance of Square Fabric
Look at your fabric. Look really closely and you'll see little lines of thread interwoven together. The lines of thread should run perpendicular to one another so that when they meet they form a perfect 90 degree angle.
When you cut a square block out of a piece of fabric and the lengthwise and widthwise threads are running parallel with the cut edges of the block, then that block is cut "on grain." This means that the edges of the block will have less stretch and be therefore easier to handle and piece.
When a block is cut "off grain" the edges of that block will want to stretch and skew very unevenly. One edge might want to stretch for more than 1/2", while another edge will only stretch 1/4". When piecing a patchwork quilt, you typically don't want any stretch in your fabric at all, so the need to cut on grain is very necessary.
There is only one time that I can think of that quilters want their fabric to stretch and that is for Bias Binding. In order to cut on the bias, you position your ruler to cut at a 45 degree angle across the lengthwise and widthwise grain.
Any block or strip cut on the bias will have an intense amount of stretch. This is very useful when needing curved binding or other decorative additions to your quilt.
So in order to get your fabric square so you can cut your pieces on grain, you first need to prewash your fabric, starch and press it, and then give it a little wiggle to get it perfectly square.
Watch this video to see just what kind of wiggle I'm talking about:
As you can see, this step to square your fabric will not take long, but it will make a big difference in how accurate your quilt pieces are cut, and how easily they piece together.