I am plugging along on the Manon. In fact, the entire back is complete, and I just finished the front left. I am part way into ball #8.
I was contemplating whether to do the right front or one of the sleeves, checking the schematic to see what the sleeve length was and trying to figure out where the top of the sleeve cap would hit my shoulder when I decided to check the width of the sweater back. It's supposed to be 19" and even though I always hit gauge, sometimes a small fraction of a stitch difference in the 4 inch swatch measurement can add up to 1/4" or more for the entire sweater back.
The back is a little more than an 1" too wide. Which means the sweater will be more than 2" too big around.
This is not good.
I laid the measuring tape across the back expanse of stockinette, where I should be getting 18 sts/4". I get 17 sts. I measured again, in a different area. Same thing.
I checked my needles, thinking I had somehow used a size 10's instead of the size 9's the pattern specifies. Nope. 5.5mm. That's a US 9.
I swatched back in September when I knit the back triangle the first time (and ripped it out for a pretty lame reason) and I know I got 18 sts/in. I made a nice big swatch, too. I almost always swatch even though I always get the gauge on the yarn label using the needles specified. For certain projects, you can use the project itself as a gauge swatch, but this was to be a sweater and this particular sweater doesn't have much stockinette until you get to the upper back. I couldn't just cast on the first triangle and use it as a swatch. There's too much texture and cable action going on. So I swatched, because I am nothing if not a conscientious knitter.
After this horrifying confrontation between my assumptions about my knitting and reality, I accepted the truth, but I couldn't understand how it happened. I stared at the gauge specification in the pattern when a horrifying realization occurred to me. I didn't use the yarn specified in the pattern, which calls for size 9 needles to get 18 sts/4 in. I used a different Aran weight yarn.
I pulled out a ball of the Sublime Aran yarn and examined the label.
Yep, I always get gauge when I use the needles specified on the yarn label. What I don't always do is remind myself of changes I have made by noting those changes in the pattern book.