Here's how I like to make tarn (T-shirt yARN) for the Tarnation Rectangle Rug pattern. It works great for me, and the 1/2" or 1 cm width makes it fairly easy on the hands and arms when working it up.
Just to know: When tarn is cut “across the grain," or horizontally across the t-shirt, its edges curl upward and inward, so that the wrong side of the fabric is mostly visible in the tarn. When cut "with the grain," or vertically on the t-shirt, tarn’s edges curl downward and inward, so that the right side of the fabric is mostly visible. The following steps will yield tarn that is primarily cut across the grain. If there is print on the right side of the shirt, it will not show. There are ways to get around this: turning out the print, and the zigzag cut.
1. Collect your t-shirts or other cotton-knit garments to be used. For best results, use items from the same manufacturer’s line. Variations in fabric content and thickness can make your project uneven. Sometimes that adds interest, but the finished product will not be as uniform, especially after washing. (For more info, see Choosing Shirts for a Tarn Rug.)
Tip: If your finished tarn item comes out of the dryer looking uneven, just give it a few yanks with your hands holding the row-ends, to straighten it up.
2. Cut the hem off the bottom of the t-shirt. If the shirt has side seams, cut all the seams off the front or back section. Save the scraps for stuffing toys, etc.
Tip: Turn the t-shirt inside-out before cutting the hem or seams off--it’s easier to see where to cut. Hold the hem or seam in your non-dominant hand while you cut with your dominant hand.
3. Cut diagonally into the hemless bottom of the shirt until you have a 1/2” (1cm)-wide strip started. This will give you a tapered end, for the needle-and-thread method of connecting strips in step 7. The ends are tapered to avoid tarn that is too bulky at the point of overlap.
Tip: Turn the t-shirt right-side-out and cut on the right side of the fabric--it’s easier to cut when the tarn edges are curling upward instead of downward where you can’t see. Also, hold the edge of the fabric (instead of the bunched-up shirt) in your non-dominant hand while cutting for better control of the fabric.
4. Tube Spiral - If the shirt does not have side seams, you can continue cutting the tarn strip, spiraling up to where the sleeves are attached. Taper-off the end, like the start of the strip.
Tip: When rolling your tarn into a ball, you can stretch the printed sections, to reduce the bulk and make them almost as flexible as the unprinted tarn. If you want the print to show on the outside of the tarn, turn it out while crocheting or knitting.
Note: If you have an allover-print t-shirt fabric, the tube spiral cut will completely hide the print. In order to make the print visible on the tarn, you must use a zigzag vertical cut technique.
5. Flat Spiral - If the shirt has side seams, continue cutting the tarn across the bottom, up the side, across the sleeve and collar edges, and down the other side. When you get to where you started, angle your cut upward so you can keep going in a flat spiral. Since tarn is stretchy, it’s forgiving at the corners, but you can round them off a little by trimming the points. Taper-off the width when you come to the end.
Note: Some tarn-makers stretch their tarn before rolling it into a ball. It makes the tarn more cord-like, but they only use tube-spiral cut tarn. This doesn’t work well with flat-spiral cut tarn--too many flappy corners and vertical cuts.
6. Cut the seams/collar/sleeve hems off any remaining shirt fabric, and cut more strips using the Flat Spiral method in step 5.
7. Connecting Strips - Overlap the tapered ends by about 1” (2.5cm). With a needle and thread, hand-sew 6-7 stitches straight up the middle. Backstitch works well for this.
Tip: Instead of tying off the sewing thread with a knot, you can take 3-4 tiny stitches at the end of the line of backstitches, to hold it in place.
Note: There are several other ways of connecting tarn, including tying a knot, sewing a diagonal seam, and cutting a slit and threading through. Your choice depends on what kind of item you’re making and how smooth the connections need to be. The method in step 7 provides a smooth connection that takes less time than the diagonal seam method.
WARNING: Don’t cut tarn across the shirt seams. The seam stitches will not hold your tarn together, especially in the wash.