Testing on Scraps Before You Commit
You've picked your fabric, you know your grain, you've made your call on prewashing. Before you cut into your good yardage, test a scrap first. Every time. Not just when something feels risky.
Here's why I'm stubborn about it. A few years back I dyed some muslin in my kitchen sink. Nothing fancy, just trying for a warm off-white. Our water here is hard, and hard water messes with dye in ways soft water doesn't. The color came out blotchy, streaky in spots, darker where the fabric folded on itself. I hadn't tested anything, because I was in a hurry and it was "just muslin." Except it wasn't just muslin once I'd dyed the whole piece and ruined it. Lesson learned the expensive way. Now I test everything on a scrap before I touch the real yardage. Skip that lesson and take my word for it.
What a scrap test catches
A scrap test isn't busywork. It catches real problems while they're still cheap to fix.
Bleeding. Some fabrics, especially reds and dark blues, bleed color when wet. If you're prewashing, wash a scrap with a plain white scrap next to it. If the white picks up color, that fabric will bleed on your whole project. Better to know now than after your runner's assembled.
Shrinkage. Different fabrics shrink at different rates, even within the same project. A cotton print and a cotton solid can shrink slightly differently. Cut a scrap, measure it, wash it the way you plan to wash the real thing, measure again. Now you know your actual shrinkage number instead of guessing.
How it presses. Press a scrap before you press your cut pieces. Some fabrics take heat fine. Some scorch faster than you'd expect, especially anything with a synthetic blend mixed in. Learn that on a two-inch scrap, not on the piece you just spent twenty minutes cutting straight.
How your needle moves through it. This one's specific to hand quilting. Some fabrics are tight-woven and stiff for a beginner needle to push through. Baste a scrap to a scrap of batting and backing, and run a few stitches. If your needle's fighting you, that's good information before you're thirty stitches into the real quilt top.
How to do it
Cut a piece at least four inches square from your leftover fabric, the stuff that didn't make the final cut. Do whatever test you're worried about, wash it, press it, stitch it, and treat it exactly like you'd treat the real fabric. Don't test a wash cycle on delicate and then plan to wash your quilt on normal. Match the test to the real conditions, or the test tells you nothing.
Write down what you learned. I keep pushing my spreadsheet on people, but this is exactly the kind of thing that's useless if it lives in your head for five minutes and then it's gone. One line: fabric name, shrinkage percent, bleeds yes or no, presses fine or scorches at what setting. Ten seconds to write that sentence, and it saves you from redoing this test on the same fabric a year from now when you've forgotten.
Where people skip this and shouldn't
Testing feels like a delay when you're excited to start cutting. But a bad scrap test costs you a four-inch square of fabric you weren't using anyway. A skipped scrap test that turns into bleeding dye or scorched cotton costs you the whole top. Not a close call. Test the scrap.
Where I'll tell you not to overthink it: if you're using a fabric you've used a dozen times before and already know how it behaves, skip the full battery. Use your judgment. I'm not asking you to test every fabric like it's a science fair project. Test the ones you're not sure about. If you're honest with yourself, you usually already know which ones those are.
Before next time
Grab two or three scraps from fabric you're considering and do a quick wash-and-press test at home, just to start the habit. Bring your notes next class and we'll talk about what you found.