Originally blogged by me in October 2009
Fair Isle and Intarsia are both techniques for knitting in more than one color. But that’s where their similarities end.
Use Fair Isle if…
The design repeats and runs along only a few rows (eg a line of Christmas trees around a hat or a celtic design around a sweater sleeve). Because Fair Isle allows you to carry the yarn along the row until it is needed, so you don’t have to rejoin a new piece of yarn every 10 stitches, which would leave a really uneven gauge with no room to adjust the tension by pulling through to neighbouring stitches in the row.
There would be a huge number of loose ends in a small space There is just no way that that 20 loose ends can be woven in neatly in a 2 inch square space.
The design calls for only a few stitches in a different colour (eg classic Fair Isle designs, like snowflakes or intricate patterns). Intarsia needs some space in which to weave in the yarn ends behind the colour of yarn used. You can’t hide two yarn ends behind a single stitch.
Use Intarsia if…
There are large blocks of colour (eg my skull and crossbones cushion cover design). There are some people who can carry the unused colour yarn behind the work, twisting every few stitches for 30/40 stitches and not have any effect show in the finished gauge. These people are brilliant and I doff my cap to them. However, most people and certainly beginners will struggle to keep the tension even enough over such a large area. This would mean that all your stitches in one colour will be one gauge and all your stitches in the other colour will be a different gauge.
You’re making anything for kids. Intarsia doesn’t leave any loops of yarn that can get stuck around small fingers.
You need to have stretch in the finished item. Intarsia work stretches just like ordinary knitting, Fair Isle does not.
Of course, in the real world, knitters very rarely restrict themselves to one technique. Within one design, you may use predominantly Intarsia technique, but switch to Fair Isle for some fiddly part of the design. The trick then is to remember which yarn is coming over and which is coming under and what happens if your Fair Isle is left leaning? But that’s a more complex discussion for another time.