This was a real problem for me at the start of my latest project. I’d previously only knitted with 100% acrylic yarn which was quite stretchy and forgiving, so although I did notice a bit of looseness when switching from knit to purl there were no actual noticeable gaps in the end result. Not so with 100% cotton.
After a bit of experimentation and asking around on the internet I’ve discovered 3 possible solutions to this problem, hopefully they’ll help someone else struggling with the same thing go right here.
Note: I also discovered that problems like this will often be reduced during the blocking process as the stitches are evened out. Since the bolero was a gift and I’m generally inexperienced, I wanted to reduce the problem as much as physically possible as I went, but blocking definitely helped sort it out even more. (thanks suzeeq and Tephra Lynn for this tip)
1) Just use a smaller needle. The ribbing in the bolero pattern, for example, called for a 5mm needle. After a frustrating afternoon of trying to get this to work I tried 4.5mm needles just to see what would happen. Answer? Tighter stitches meant the gap was immediately much less noticeable and my ribbing was generally a lot neater.
2) Pull the yarn tighter. At first when trying to solve this myself I was trying to keep everything as tight as possible at all times, but this (rather unintuitively I must say) can actually make the problem worse, not to mention the agony your hand will be in after a while of this. The best thing I found to do was just give an extra tug on the working yarn AFTER inserting the needle to purl but BEFORE wrapping the yarn. I’m a “thrower” so can’t speak for alternative styles.
3) If the gap is still causing problems, Shadow Byrd shared an interesting approach.
I’ve found that if I purl backwards then it shortens the space between knit and purl stitches and fixes that a bit. When you come back around to that one you need to purl through the back stitch to keep it from twisting.
Being a newb I had to ask for clarification on the “purl backwards” part, all this means is wrapping the yarn backwards when you purl (so clockwise instead of anti-clockwise). This isn’t something I’ve attempted yet but the technique is bookmarked in my brain for future experimentation.