I have been asked the best way to create a provisional crochet cast-on. We will be using it several times with the Roses, Roses pattern. I hope that this helps.
A provisional crochet cast-on is used when the pattern you are using calls for the stitches that are cast-on to be used to knit from at a later point in the pattern. The stitches are picked up from the back bump on the crochet chain and at a later point the chain can be removed and the then “live” stitches can be knit from.
To keep the process easy use a contrasting colour yarn that is very smooth and not too much heavier than the yarn you are working with, a cotton or a slippery yarn can work very well.
When looking at a chain the smooth, right side looks like a row of knit stitches and the wrong side looks like a row of bumps. You will pick-up your stitches through these bumps. You will only need one needle to pick-up the stitches.
Do not make the crochet chain too tight. I usually chain at least ten more stitches than I need, that way I can skip a bump in the chain, if the chain bumps are starting to tighten up.
With crochet hook and contrasting yarn chain the stitches you need plus 10. Cut your yarn and pull the end through the last chain made. Put a lock stitch marker on this end if you need to. This will help identify the end that you need to pull out.
*Pick a bump close to this end and push your needle through the bump, wrap your yarn around the needle tip and pull back through the bump and you will have a new stitch on your needle; repeat from the *, until you have enough stitches on your needle.
If the bumps start to get tight just skip one and go to the next, this will allow you to keep enough ease in the chain to make it easy to pick-up from. Once you have picked up your stitches work your pattern as from a regular cast-on.
Removing the stitches from the crochet cast-on will usually leave you with one less stitch than when you started. Use your tail yarn to cheat a stitch in or create a new stitch with a M1 when knitting your first row.
When you are ready to remove the crochet chain and work with the stitches work as follows.
Starting at your marked end, and working on the wrong side of your work, pick-up the stitches showing through the crochet bumps with your working needle. It is sometimes easier to pick-up those stitches with a smaller needle and then slip them onto your working needle.
Undo the finishing stitch for the chain. If you have made a “clean” (no threads caught) pick-up and not caught any threads the chain will pull right out and your stitches will be ready to use. If your pick-up was not very “clean” you may need to carefully clip the caught up threads before you can finish removing the crochet chain.
Once you have successfully created a provisional cast-on with the crochet chain and used it a few times – the technique will become something you can do without any qualms. It has quite a few uses beyond lace knitting, though it is in lace knitting that you see it the most. Especially when creating the tabs at the back of the neck of top down shawls. These tabs give a starting point for many types of shawl.
For example, I have used a provisional cast-on when starting a Faroese shawl or when starting a sweater. I could not decide what kind of start, ribbing or lace, I wanted for my sweater so I started with the provisional cast-on and then went back later and added an edging.