I just received a comment on an old post about learning to knit using one circular. Now, I'm not quite positive on what is meant by the question--knit in the round on one circular, knit "magic loop" style on one circular, or knit two items at the same time on one circular. So, hey, I'll just address all the possibilities. Beats folding laundry anyway!
I do not know when I learned to knit circularly on one circular needle. Fairly early in my renewed knitting experience (having learned to knit as a child, I didn't accomplish ANYTHING until my 4th year of university when I wanted to show up my housemates who were learning to knit. That was the fall of 1993) I followed the pattern's instruction to use a circular needle to pick up stitches for neckbands. I'm sure I was probably confused as to how to knit back and forth on one circular, LOL. Just the concept of holding the needle with the 'work' in the left hand, and the empty needle in the right hand, could confuse me. I'm sure there's instructions on the internet on how to knit flat with circulars and obviously I figured it out.
Knitting circularly on one circular needle. I'm not sure when that happened. However, I know that in March and April of 1999, I took a class on knitting socks, and I'm pretty sure this was the first time I knit on dpn and knit circularly. Wow. I'm surprised it took me that long. Really? When I knit Rob's long, fair isle stocking cap, I knit it flat. I don't recall many of my projects from back then--some sweaters, an adorable dress for my niece, her Christening outfit too...yeah, they were all knit flat.
Back in 1999, there wasn't a whole lot on the internet (in general). Digital cameras were not popular, so forums rarely had pictures; blogging was in it's infancy; there was no Facebook, no Ravelry. The library was still a primary source for information, and all too often these days people seem to forget that the library is still a great resource.
So, I started knitting socks, and got immediately hooked. Bought dpns like they were becoming extinct. My first sock, during that class, was knit inside out for the leg. I got corrected the next week, and now can't even figure out how to do that again, LOL.
So, when did I first knit circularly on circular needles?! Mmm. Maybe when I was on a hat binge (but when was that?). Maybe when I made some LionBrand Homespun hooded pullovers...that was early 2002. I think I might have made them circularly. Indeed, I just checked the one that got handed back down to my son, and there are no side seams. If I could find my old knitting photo album, I could find out more.
Learning how to do this though? Knowing myself, I can only imagine the mental block I had. "Join, being careful not to twist stitches". No one tells you that knitting the first st that you cast on, onto the right needle, is how you 'join'. I was trying to find some way to 'join' it, and then knit the row. I think the way you cast on determines how easy it is to get this concept.
I couldn't even figure out what that really meant by the 'do not twist' until one time, it happened, and I unknowingly knit a few rounds of a mobius. I did find that even if you get to the end of the first round, and find a twist, it's unlikely to show in some yarns, LOL. On dpns you can untwist the last needle, but you can't on circulars. So then I learned to knit one or two rows flat, then join into a round, and sew up the tiny seam after. In order to join the cast on row without twisting, I would usually sit on the couch, put my knee up in front of me, and spread the knitting around my knee, aligning all the sts. And knit like that.
Magic Loop. It wouldn't surprise me if I had 'accidentally' done Magic Loop before I knew it. Sometimes, the cable connection gets kinked and sticks out all on it's own while you knit. I'm sure I also got frustrated with knitting the top of a hat, and not wanting to get off the couch to find the dpns, I stretched out the cable to see if I could knit just a bit more. I did 'officially' learn Magic Loop in May 2007. But it wasn't all smooth sailing. I know that link takes you to the first post, but if you click on the "May 2007" or other months that summer, you'll see some other examples. It took me a long time before I could cast on this way, and for knitters who want to try Magic Loop, I do recommend starting the project however they normally do, and switching to Magic Loop once it's going well. Depending on your cable length, you can just pull out the extra cable on the right needle before starting the round, or you can pull out the cable at the mid-point too (for shorter circular needles). Be careful with marking the start of your round though; you won't be able to tell from your cast on tail as the knitting naturally spirals. There are lots of websites that tell you exactly how to Magic Loop, so I won't bother, but I think those two tips can really help.
Two at once. This can be done on one circular, or two circulars (I won't write about knitting in the round on two circulars as if they were 4 dpns; it's a fairly straightforward idea). I still have trouble casting on, and still recommend casting on separately and knitting about an inch. Then, if you've done Magic Loop, it's fairly easy to see that you'd have 1/2 the sts of the first item, then all the sts of the second item (pulling out the cable at the mid-point), then the second half of the sts from the first item. That's the hardest part for me (esp. if actually trying to cast on for both items at once). If someone has good instructions for how to cast on two items on one circular, I'd like to know! It might be easier to cast onto two circulars, but then you have more ends flopping around. And, of course, to do magic loop for two items at once, you do need a really long cable. So, quite often, I might start as magic loop, but then as the toes of the socks increase, it gets harder to do Magic Loop and I switch to two circulars.
I'm sure I haven't answered her specific question, LOL. I say, just Google it, or go to the library. There are tons of videos on YouTube as well, for knitting!