Gauge or Tension
Obtaining an accurate gauge ensures achieving the correct measurements and proper fit as stated in the pattern instructions. I get many customers, even experienced knitters who look at me funny when I ask them to do a gauge or tension swatch. With practice making swatches becomes a habit.
Gauge is simply the number of stitches and rows per inch of knitted fabric, and determines the size of the project. Well written knitting pattern instructions begin with the gauge, usually given for a 4"(10cm) square of knitted fabric when using the yarn and the needle size specified.
Before beginning any project it is strongly recommended that you make a test swatch at least 4"(10cm) square using the yarn and needle size indicated in the pattern. Striving for accuracy is well worth your time and will avoid disappointments after many hours of knitting.
Using the needles and yarn specified in the pattern, cast on the required number of stitches to obtain at least the 4"(10)cm swatch. For a more accurate measurement add a few stitches at either end, working a garter stitch border. When making a swatch for lacy patterns, it is best to make a 6 to 8 inch swatch. When working with mohair or other highly textured yarns it is difficult to count stitches, therefore cast on the exact number of stitches given in the gauge and measure the entire swatch, or use stitch markers on either side of the required number of stitches for the gauge.
Knit the swatch in the specific pattern stitch used. Often the gauge is given in stocking stitch (stockinette stitch). Work the number of rows indicated and I usually add an extra row or two. Instead of binding off the swatch, cut the yarn and run it through the loops with a tapestry needle. This allows for easy measuring, as binding off will most likely make the top of the swatch tight. However, with a lacy pattern or a very stretchy stitch pattern, bind off the last row. Except for synthetic yarn, I recommend blocking the swatch so that it lies flat and is easier to count the stitches and rows.
Some patterns incorporate more than one pattern stitch. If the gauge is the same for all pattern stitches, it is best to work a large swatch using all the stitches. Often, a variety of stitch patterns will not be the same tension, therefore a swatch is necessary for each pattern stitch and needle size.
Measuring the swatch
After blocking the swatch, pin it on a flat surface. Do not stretch the swatch, unless the swatch is ribbed. With ribbed patterns, the instructions will often say stretch slightly when measuring. This is because a ribbed fabric is elastic, and conforms to the body shape, therefore it is measured in a pulled state.
Measure the gauge using a tape measure or stitch gauge. I prefer a tape measure. Count the stitches across, inside the garter stitch border over the 4 inches closer to the middle of the swatch, or measure the full width of the swatch with a tape measure depending on how you knitted the test swatch. Count carefully, as half a stitch can make a difference to the finished size of the piece.
Row gauge is also important for complex stitch patterns, shaping pieces such as sleeve increases, and shaping other body pieces. With the test swatch, count the rows vertically in a 4 inch area with a tape measure or stitch gauge.
If your stitch and row count is the same as in the instructions, you can begin knitting, but measure your project after you have worked about 6" to be sure the gauge is accurate.
What to do when your gauge is different from the pattern instructions?
Because you did not obtain the same gauge as in the instructions does not mean you cannot make the item. All it means is you have to play with different needle sizes to obtain the correct gauge.
Knitters are individual in their knitting style, thus they will often obtain a different gauge, even when each uses the same yarn and needle size. Some people tend to knit tight, while others knit loose. If your swatch measures fewer stitches per 4", your work is knit loosely, therefore knit another swatch using smaller needles. Start by decreasing the needle size by 0.5mm or 1mm. Continue making swatches until the gauge matches the pattern instructions. If your swatch measures more stitches per 4", your work is knit tightly, therefore knit another swatch using larger needles, increasing the needle size by 0.5mm or 1mm increments. Often times, the second swatch is all that is needed. With experience you will understand your own style and this will not be such a tedious task. Write down the yarn and needle size needed to obtain the gauge, and the next time you are using the same yarn and needle size, you will not have to do another swatch.
With all those swatches you collect, they certainly can serve other purposes. Here are some suggestions: sewing squares together to make a blanket, testing colorfastness and shrinkage when wet cleaning, appliqued to other items, wall hangings, testing embroidery techniques, as well as many other creative solutions.
Substituting Yarns in Projects
Sometimes it is not possible to find the yarn asked for in a pattern, so a substitute yarn is necessary. A good rule of thumb is to use a yarn with similar strand width, texture, and the amount indicated in the pattern. For example, say the pattern for size small requires 15 50g balls (100m each) of a double knitting yarn. Double knitting yarn is a common thickness of yarn and there are lots of double knitting (DK) brands. In this example, multiply 15 (balls) by 100m (each) which equals 1500m , the total meters required for the pattern. Let's say the yarn you are interested in has 110m per ball and is a DK yarn, therefore, divide 1500m by 110m which equals 13.6. Round up to 14. Purchase 14 balls of the substitute. The best way to ensure an accurate gauge with the substitute is to make a swatch and compare to the gauge of the pattern. Substitution becomes easier with knitting experience.