There are some crochet stitches that you might not use that often, but they are still something you want in your crochet stitch kit because when you need them, nothing else will do.
For me, one of those stitches is the foundation double crochet, and today, I found myself needing it for a design I am working on.
Unlike a standard double crochet foundation where the double crochet stitch is worked into a separate (but connected) foundation chain, the double crochet foundation stitch consists of a foundation chain and double crochet stitch all wrapped into one.
It’s a little stretchier and a little taller than a double crochet worked in the traditional chain foundation, but sometimes that extra stretch and added height are exactly what you need.
For a standard foundation, you start out with the easily recognized chain. For purposes of demonstration, I have used a worsted weight yarn and a 6.0 mm or J hook to make a foundation chain:

Then, after pulling up a loop and making a yarn over, I inserted the hook through the back ridge loop (my usual point of entry for a foundation chain):

Then I completed the double crochet stitch into that first chain and continued on my merry way into the back ridge loop of the next nine chains. In short order, I had a foundation ten double crochet stitches wide from which to work:

Next, I made a double crochet foundation using the technique demonstrated in this video:
and I got a foundation double crochet that, like my first effort, is ten double crochet stitches wide:

They don’t look all that different, but when you put them one on top of the other, it’s a little easier to see the slight curve and added height of the foundation double crochet stitch (bottom):

I don’t yet know if my plan to use this stitch will work as I expect, but I know that I won’t reach my goal until I at least give it a whirl, and as always, I will move forward, one stitch at a time.
I had noticed the curve that results with these combination foundation stitches too. I occurs in a foundation sc as well as a foundation dc (US terms). I use this property to great effect with ribbing in the round; e.g. hat bands.
Your blog entry here is the first time I have seen anyone else acknowledge that these handy foundation stitches do create a curved finish. It might be easy for a beginner to think that they had done something incorrectly if they were expecting a dead straight foundation like the normal chain foundation.
Perhaps further experimentation with working tension might make a difference to the curvature of rows made with foundation stitches. What do you think, Leslie?