When you're substituting yarns for a pattern, knitters know that if that pattern calls for a worsted weight yarn, that substituting another worsted weight yarn is the thing to do.  But all worsted weight yarns are not the same.  Some yarns like cotton are inherently heavier than yarn made of angora.  But even within the vast area of Worsted Weight Wool, you'll find balls of yarn that will weigh differently.  

Why does weight matter?

When you finish your garment, you will either end up with a fairly lightweight sweater or an extremely heavy one.  If you're doing a lot of cables which takes more yarn, a sweater knit with a heavy fiber will be even heavier.  This affects your shoulder seams, the neckline drop, the sleeve length, and the overall comfort.  If you're knitting with lace, a heavy yarn will really widen the openwork and leave you holes bigger than you wanted.  Brioche uses almost twice as much yarn as stockinette, so you'll definitely want to minimize the total weight.  

In these cases, you'll want to select a yarn that weighs less.  This is a yarn that gives you more yards per gram in each ball/hank/skein.

On the other hand, if you're working with a "puffy" stitch pattern that you want to lie flat, a heavier yarn will help pull the garment down and stretch out that pattern to a pleasing texture.  If you're working with elongated stitches that only look cool when actually elongated, you don't want a yarn so light that the dropped yarn overs puff out and glob together.  You want them stretched out to give the full effect. 

In these cases, you'll want to select a yarn that weighs more.  This is a yarn that gives you less yards per gram in each ball/hank/skein. 

Also think about the size.  You can use a heavier yarn with a Woman's XS than you can with a Men's size 5X. 

When substituting yarn for a pattern, first figure the weight per yard of the yarn listed in the pattern.  Divide the total grams by the total yardage on the ball band to find out how many grams one yard of yarn weighs.  This is easier to do in grams than ounces since with ounces you'll end up with a slew of fractions to contend with.  

Below is a comparison of WORSTED WEIGHT YARNS, ranked from lightest to heaviest:

As you expect, the cotton blends are the heaviest.  But look at the difference in wool!  There's a big difference in Brooklyn Tweed Shelter at 0.36 grams per yard compared to Sugar Bush Bold at 0.53 grams per yard.  A sweater that uses 1300 yards of yarn will weigh 468 grams with Shelter and 689 grams with Bold.  That is a substantial difference that you will notice as soon as you pick up the garment.  

Sometimes you want it light, sometimes you want it heavy.  But knowing that the weight will have an effect on the finished garment, is an important tidbit to tuck away in your brain.

Before you make your next substitution, think about what you're creating and how you want it to behave.  Then grab your phone to do a quick calculation to figure out how much one yard of yarn weighs before purchasing your yarn.  When you invest time and money into a hand knitted garment, you want it to turn out the best that it can be.  This quick little trick helps to do just that!

Happy Knitting,
​Donna

Ages ago, I walked into my local yarn shop and said I was done with superwash yarns.  Sweater after sweater ended up so much larger than the pattern called for and had super long sleeves that were unwearable.  Yes, I had swatched, and I had knitted the pattern exactly as written, but ended up with an expensive, time wasted mess. 

With more and more amazing superwash yarns popping up, the desire to knit with them is becoming irresistible. When wool yarn is treated to become "superwash" it is stripped of it's natural elasticity properties.  It won't spring back into shape after being soaked in water.  It grows in size.  And this can ruin a carefully hand knit garment.

But there is a way around this.  You can knit with a superwash yarn and have your sweater turn out as expected.  You just need a bit of planning and math.  (just a little).  

I always list in the notes section of my patterns that are worked in superwash yarns, to measure lengths vertically with the weight of the garment hanging from the needles.  But there is just so much explanation that you can write into a pattern before it becomes tedious to read, especially for knitters who are already know this.So I'm taking a few moments to elaborate here, and arming you with the knowledge and steps to take to be able to knit a garment that fits with superwash yarns. 

1.  Knit a swatch.  As a wise knitter told me once, "We all knit swatches after all!  We either knit 4x4" swatches or 18x20" swatches."  With superwash yarns, this is a must!

2.   Measure the UNBLOCKED swatch.  Write down your stitch and row gauge over at least 4".

3.  Block it.  Soak it in water, roll it in a towel,  lay it flat, pin it and let it dry.

4.  Unpin it and fluff it out.  Lay it back down and with a ruler, measure the dry, blocked swatch and again write down your stitch and row gauge over 4".

5.  Your stitch gauge, after blocking, must equal the stitch gauge of the pattern.  Some patterns list both the pre and post blocking gauges, and if they don't, it is standard practice that patterns will list the gauge after blocking. If your stitch gauge doesn't match, try a different needle size, make a new swatch, and measure it before and after blocking.  

6.  Once you have a blocked swatch that matches the pattern's stitch gauge, use this swatch and figure the percentage that your swatch lengthened. Compare your pre-blocked row gauge to the post-blocked row gauge. If the pre-blocked row gauge is 32 rows=4" (8 rows=1") and after blocking it's 28 rows=4" (7 rows=1"), 8 div by 7=1.14.  The length increased by 14%.  You can also measure the new swatch.  If the old one was 4" and the new one is 4.57" 4.57/4=1.14.  

 If the swatch is 10% larger, then it increased 110% of the original size.  This equates to (110/100) or 1.1.  This is the number you'll need.  
       10% = 1.1
       15% = 1.15
       20% = 1.2
       22% = 1.22 etc. 

(If blocked is 10% larger, you can't just reverse it all and say the pre-blocked swatch is 90% smaller.  It's close, but not accurate.)

7.  Back to row gauge!  If your blocked swatch was 10% larger, you'll divide by 1.1 remember.  Use this knowledge when knitting lengths.  When a sweater says to"work until piece measures 18" and divide for armholes", you'll want to lift your needles up and measure the length with the weight of the piece hanging from your needles.  Place the tape measure just under the needle so you're measuring the last row of stitches worked that are lined up under the ones that are on the needle.  Let the tape measure hang until it reaches the bottom.  You'll stop knitting when you've reached the length called for in the pattern, in this case 18" divided by 1.1 which equals 16.36".  That is a big difference, especially if you're working sleeves.

Since you've done the pre/post block experiment, you know that, in this scenario, a piece of knitted fabric measuring 16.36" unblocked, will grow 10% after blocking and become 18".  The percentage changes with every project.  Yarn, needle size, tension, and stitch pattern all affect the percentage of growth.  So you'll want to do this every time you're knitting with superwash yarns. 

If you're unsure of your math, or just nervous about proceeding, you can always stop 3-4" short of the length that the pattern states to knit to, take a tapestry needle threaded with yarn and run it through all the stitches, remove your needles and soak the unfinished piece.  Block it and measure it after it's dry.  This will help you to figure out how much more you need to knit before proceeding.  Once it's dry just re-feed your needle into the stitches, remove the waste yarn and continue on.  You can always start knitting the sleeves or front while it's drying, because we need to keep knitting right?

There are many reasons why you might end up knitting with a superwash yarn, and I hope this helps you to knit garments with confidence.  You've mastered the hardest part - knitting stitches into a lovely fabric.  By tweaking your process just a tad, you'll end up with a garment that fits.  And expand your repertoire of yarns in the process.  

If you have any questions, please ask here.  (It's not a live a chat, the link will direct you to an email, just so you know.)