The most important question you need to answer is: How much strain does the finished corset have to withstand?
If you want a drastic waist reduction via tight-lacing, the entire corset will be under enormous strain. You'll have to use very strong materials for the fabric, the sewing thread and the boning. If you want a slightly stiffened bustier as a form of shapewear, you can choose lighter, more flexible materials.
Cording
This is a mostly overlooked historical method of creating shapewear that holds its shape very well but stays flexible and doesn't impede movement. It's bendable in every direction and makes for a very comfortable garment.
You'll need 2 layers of fabric that are slightly wider than your pattern piece and a type of string or cord that is stiffer than knitting yarn but not too thick. 1 - 3mm hemp or sisal string from the gardening department worked well for me. You should not use wired string or the wire may rust and destroy your corset.
Instead of sewing boning channels onto the fabric, you sew both layers of fabric together to create cording channels between them. You can either measure and sew first and then pull the cording through the channels or you lay the cords between the layers and sew it in with a zipper foot.
A corded section looks ike this. Find this image and detailled instructions in this blog by corsettraining.net.
Since cording cannot break or poke you, it's suited for tight-lacing as well as soft corsets or corseletes, but since it lacks stiffness it cannot support certain silhouettes or free-standing bits.
Synthetic baleen
There is a plastic boning that is marketed as synthetic or "German" baleen. It comes in long strips that can be cut to length and the ends rounded with a file. It can be molded when warm and molds itself to your body when you wear the garment. Because of it's flat shape it's mostly bendable in one direction (forwards & backwards), but less so perpendicular to that.
It is the closest thing to real baleen that is currently available. You only need a few strips of baleen to give a corset a stiffness and flexibility that was common in historic pre-1970s corsets (or rather "stays" in this case). It is not suitable for tight-lacing or waist reduction because it can break under stress.
Zip ties
The crafty alternative to artificial baleen. The properties are very similar: it's thin, lightweight and flexible. But zip ties don't mold themselves to the shape of the wearer. On the contrary, they are intended to be bent around cables and stay in that shape. So corsets boned with zip ties suffer from permanent bending of the bones, for example after sitting or bending down.
Like baleen, they are not at all suitable for tight-lacing because they tend to permanently bend into tight corners that poke you in the ribs.
Modern plastic boning
These come as woven fabric tapes that have thin plastic wires woven into them or as long plastic strips, sometimes already encased in fabric. The wider varieties usually are stiffer than the thin ones, but overall they are very flexible. The big advantage is that you can simply sew over them without encasing them in boning channels.
Here's one example called Rigilene or Featherweight with 8 plastic wires:
They are commonly found in modern wedding dresses or haute couture garments. They are very practical, easy to use and almost invisible. The narrow ones have almost no stiffness, which makes them viable for garments made of soft, drapey fabric. The biggest difference to artificial baleen is that they don't mold to your body.
Spring steel boning
If you want waist reduction and/or tight-lacing this is the only viable option for you. Even if you don't want to tight-lace, it's good to have a strip of metal boning right next to the lacing holes for added strength.
In contrast to all other materials, spring steel is only bendable in one direction. That gives it unique properties that you wouldn't want in many historical stays, but need for the typical wasp waist corset.
Steel boning is usually sold in long strips of several meters / yards. You'll need metal shears to cut it to length. I tried cutting it with nippers and couldn't get through it. It's also available in pre-cut lengths.
You'll also need to cover the ends of each boning strip to keep it from tearing through the fabric. There are small metal caps available for that purpose and a rubber-like dip that dries onto the metal. I've used the metal caps and they work well, but are fiddly to get on. The dip should protect the metal from rust (at least in theory), but I have no experience with that.
Spiral steel boning
Although it's made of metal, it's rather flexible and soft. It's very comparable to artificial baleen with the exception that spiral steels can bend in all directions and don't mold to the wearers body.
It's easier to work with that spring steel because you only have to nip through a steel wire to cut them to length. There are also metal caps and dipping solutions available to protect your garment from the sharp edge.
Wooden busk
This is a special item that was only used in historical stays but fell out of fashion with the invention of metal corset closures.
It's a smooth strip of wood the same length of the stays that was inserted into the very front to keep the stays straight and force an upright posture. There was always only one busk in a pair of stays.
Apart from the sturdy and not bendy busk, wood was not used as boning.
Here's an extant ca. 1830s pair of stays with a wooden busk inserted in the center (image source):
So how do I choose?
If you want to make a historical costume, try to get as close as possible to the historical materials. Depending on the time period, the most common boning materials were baleen, cording or steel.
If you cannot get artificial baleen, try spiral steel for a very tight corset and zip ties for a pair of stays without waist reduction. Simply using a stiffer fabric or an additional layer of fabric also adds stiffness.
Historically the center back where the lacing holes are was more reinforced than the rest of the corset. Especially at the very edge, where the lacing string would pull most on the fabric, there were often either 2 strips of baleen used or a narrow spring steel, even if the rest of the corset was boned with baleen. This prevents the lacing holes tearing out.
If you want to make a modern corset, corselette or similar shapewear, it depends on the intended use.
- Spring steel is the only option for tight lacing wasp waist corsets.
- Spiral steel offers very much support for heavier figures and moderate waist shaping. Keep in mind that it can rust, so washing the corset is a problem.
- Artificial baleen is very comfortable while providing a lot of support. If you need a lot of bust support but want to wash your corset regularily, this is a very good option for you.
- Modern plastic boning is very versatile (due to the varied widths) and work for corseletes as well as lingerie. It doesn't offer much support, though.
- Cording is probably the most accessible material and offers moderate support.
