I love to do bobbin work which is working with a heavier thread in the bobbin, sewing on the reverse side so the bobbin thread shows on the right side.
Sometimes it feels a little awkward. I've heard students say things like - "it's like working backwards or blindly", but once you get beyond that, it's really great fun and quite easy. It's especially pretty when you set your machine for a decorative stitch and use the heavier thread. It's almost looks like beading as you can see in the details above and below.
or sometimes just a straight stitch to emphasize the shape of something like in the petals below.
To start, you need to have 2 different threads in the same color - the heavier couching thread and the top thread which can be decorative or a regular sewing thread. The threadwork is strictly decorative so using a rayon thread in the top which is a weak thread will work fine. There are many good couching threads available - YLI has Candlelight, Madeira has Glamour, and Razzle Dazzle by Superior. All are heavier threads and need to be used in the bobbin, they will not fit through the eye of a needle. Below is Candlelight and a matching color rayon. You can also use a monofilament in the top.
Because the threads have different weights, the thinner thread will wrap itself around the heavier thread and be seen, so it is necessary to use matching or clear thread on top.
To sew, sometimes it's obvious where to sew while working from the wrong side. On the red hat, the band on the brim and the circle at the top had already been appliqued down and the stitching showed on the wrong side. The lines were there as a guide. Sometimes the area you want to sew is not obvious and you need to mark it with a line of stitching.
Winding the bobbin is done on the machine, no need to hand wind. Because the thread is heavier, a bobbin will hold a lot less - so it's a good idea to wind more than one up front.
One of the reasons I love Candlelight and use it in my workshops is because 99% of the time, no adjustment is needed on the bobbincase. I know many fear touching the bobbincase tension. If you like doing this kind of work, it's good to invest in an extra case for that purpose. It's easy to adjust using the little screwdriver that comes with your machine.
On the removeable bobbincases, the screw is where you see it in the picture, to tighten, turn right, to loosen, turn left (remember...lefty loosy, righty tighty). The screw in a bobbincase is very short so work with a cloth underneath you - if it should fall out, you will find it easily.
Set your machine for a decorative stitch - this may take some experimenting - ones that look great in a normal weight thread don't always work in a heavier thread. When I first started doing this, I made a sampler and labeled the stitch # - a little time consuming but a good reference down the road.
Pull up your bobbin thread, feed dogs up and traditional sewing foot on.
Before taking the first stitch, pull the bobbin thread up through the fabric so you can see both threads (on wrong side). This will avoid a tangling or mess underneath (on right side). Start stitching using the marked line as a guide. The easiest way to do this is to watch the little groove going down the middle of the presser foot - make sure it's on the marked line.