This pattern is great for using up leftover bits of yarn. Because you knit a circle until you have reached the bottom diameter of the carafe, it is easy to adjust for a variety of gauges. I have knit this successfully with Cascade 220 and also with a fingerng weight. Instructions are given for the fingering weight.

There are few decreases to shape the collar; most of the shaping comes from the way welts push outward, and ribs push upward.

Trace the bottom of your chemex onto a piece of thin cardboard, following the edge of the base in contact with the table. The profile of the Chemex will continue to widen above the very bottom. The circle you trace will be slightly smaller than the fullest width of the Chemex.

Cast on 6 using Emily Ocker’s circular cast-on. Divide stitches evenly onto three size 4 needles.

K1 front and back; repeat from 6x. You now have 12 stitches total.
Knit one row
K1 F+B, K1; repeat from 6x. You now have 18 stitches total
Knit one row
K1 F+B, K2 place marker; repeat from 3x. You now have 24 stitches total.
Knit one row.

Continue in pattern until you have 48 stitches total. Divide stitches evenly over four needles, with 12 stitches on each needle.
Continue in pattern until you have a circle the size of your cardboard tracing.

Purl all stitches for 6 rounds in fingering weight, or 4 rounds for worsted weight. Keep the markers in place, because they will help keep when you switch to a wide rib.

You are aiming for a 4x4 rib for the collar. If you have a number of stitches already divisible by 8, you may go straight to a 4x4 rib.
For numbers that are not divisible by 8, evenly add a purl stitch as needed. For example, if you have 108 stitches, or 18 stitches per section, you would have a sequence of 4 knit, 5 purl, 4 knit, and 5 purl. If you have 102 stitches, or 17 stitches per section, you would have a sequence of 4 knit, 5 purl, 4 knit, and 4 purl.

To achieve the 4x4 rib, knit a few rows, then decrease 1 purl stitch per section, or 6 stitches per round. If you need to decrease again, wait a few more rounds before following with another decrease row.

Cast off when you like the height. I find an ordinary cast off has enough elasticity.