Since the yarn I used for the soon-to-be-published Lace Cable Rib Pulloverhas been discontinued, I have swatched with a number of possible substitute yarns to make sure the proper gauge can be achieved. When substituting yarn, it is especially important to knit a good-sized gauge swatch and measure it after blocking.
I chose possible yarns based on ball band gauge and fiber content, hoping to find yarns with similar drape and weight. This proved to be rather difficult! The Tilli Tomas Fil de la Mer is in a sort of in-between class, on the light side of DK and on the heavy side of sport. My comments are below.
Clockwise from top left:
Debbie Bliss Prima, 80% bamboo, 20% merino wool, 100m/50 g skein, color #35704, using US size 4/3.5 mm needles. Nice luster and drape, quite splitty (as Ysolda pointed out in a comment on an earlier post), a bit on the heavy side (it has 100 m per 50 g, compared to the Fil de la Mer at 128 m per 50 g).
Misti Alpaca Tonos Pima Silk, 83% pima cotton, 17% silk, 327 yds/100g skein, using US size 5/3.75 mm needles. Gorgeous subtly variegated color, a bit of sheen, really nice to knit with, not quite as drapey as the Fil de la Mer, but I really liked this yarn a lot. It also comes in solid andhandpainted colors (although my preference would be for the subtly variegated or solid colors for this pattern).
Classic Elite Allegoro, 70% cotton, 30% linen, 152 yds/50 g skein, color #5650, using US size 5/3.75 mm needles. Quite lightweight (a good thing, in my opinion), nice dry hand, moderate drape, a matte surface without much luster, knits up a tad loosely (I first tried US size 6/4 mm needles, but then went down a size, and I wouldn't be surprised if a US size 4/3.5 mm needle was required for some knitters to get the proper gauge). I liked this yarn, but it is quite different from the Fil de la Mer.
Patons Grace, 100% cotton, 136 yds/50 g skein, color #62246 Leaf, using US size 6/4 mm needles. Nice stitch definition and sheen, but the fabric has a crisp feel and lacks drape; I ended up not including this as a suggested substitute in the pattern, even though I achieved the correct gauge.
Frog Tree Picoboo, 60% pima cotton, 40% bamboo, 116 yds/50 g skein, color#1000, using US size 5/3.75 mm needles. Nice sheen and soft hand, a bit on the heavy side, moderate drape.
Mirasol Nuna, 40% merino wool, 40% silk, 20% bamboo, 191 yds/50 g skein, color #1009, using US size 5/3.75mm needles. This is a very lightweight yarn with a lot of luster; a pleasure to work with; more bounce and less drape than the Fil de la Mer, but this and the light weight will actually help the sweater hold its shape (as I state in the pattern, with the Fil de la Mer you can expect the body and sleeves of the sweater to stretch an inch or more in length while worn--this may not be the case if using the Nuna). This swatch wanted to be a tiny bit small, so if you decide to use it, block heavily and make sure you can get the right gauge. Lots of lovely colors.
I also swatched with Louet MerLin sport weight, a merino wool/linen blend (I used the worsted version of this yarn for a recent unbloggable project and liked it), but it knit up at too fine a gauge. Finally, after I did all this swatching, I noticed the tempting Madeline Tosh Pashmina on a website somewhere, and I think this could also work nicely. As always with MT, the colors are just amazing. It's 75% wool, 15% silk and 10% cashmere, so it would probably be less drapey than the Fil de la Mer.