There’s a lot of confusion and misinformation about corset bones that get circulated. I mean, first of all, why are they even called bones? The term originates from whalebone, which wasn’t bone, but baleen, the filter-feeding system used by some whales. Then there’s the raging debate as to whether flat steels are superior to spirals, or vice versa. Flat steel boning is made of strips of spring steel sheets, carefully blunted on its sharp edges and coated with a rust protectant. Spiral steels take the form of a flattened coil, carefully capped, and are noted for their greater mobility.
Well, not to cut myself off here, but there is no objective superiority between flat (spring) and spiral steel corset bones. It all entirely depends on the intended placement of the bone and intended use of the corset. Which is to say, there are advantages to both types – depending on the circumstances. When ordering or purchasing a corset, knowing your preferences and needs regarding boning can be incredibly valuable. (Corsetieres interested in learning more on the subject will probably enjoy Jenni “Sparklewren” Hampshire’s post on Foundations Revealed, “Comparing Steel/Spiral Boning.”)
First, it’s important to note that boning comes in various qualities, like every other corsetry compenent. And I don’t just mean quality as a good/bad spectrum, but rather attributes. Before my last trip to England for the Oxford Conference of Corsetry, for example, I had never encountered flat steels so stiff! Except, perhaps, in my English-made Sparklewren cincher sample some years prior. Whether that’s a feature or deterrent depends entirely on the intended use. Also remember that boning only supports and enhances the shape enabled by the fit patterned into the corset.
Lacing bones, which have pre-cut holes for grommets, are generally noted to also be quite stiff. On some figures, this may equate to greater stability; on others (such as curved sway-backs), this may create uncomfortable pressure. Even without lacing bones, though, it seems to be universally agreed that the grommets at center back must be supported by flat steel bones. (If there are any exceptions to be had, I would love to hear about them in the comments below!)
Conversely, spiral bones are always needed on any seam that has a lateral curve as well as a vertical contour. Any bone channel that is curved on a style line (rather than tracing a straight line down a curved form) will certainly require a spiral steel bone. Depending on the style of corset, spiral bones may be required to fit the style line.
On plus size figures, I’ve heard it both ways. “Flat steels are too poky, and dig in!” versus “Spiral steels aren’t supportive enough!” Ultimately, this means that it may just come down to personal preference, which is no help when shopping for your first corset. (Sorry.) On bony figures, though, I would almost always recommend spiral steels. If you have a highly compressible rib cage, it may not be an issue, but with protruding ribs and hip bones, flats are liable to cause bruising. I always describe spirals as being able to achieve a “more complex” contour – they easily trace the swell of a bust, then the curve of the ribcage, a subtle indent of the waist reduction, and then gracefully round the hip bone. This is why some corsetmakers use spirals for seams that cover the bust, even if they use flats in all the other channels. A spiral bone, unless pre-contoured or broken in to a certain curve, will skim the outermost convex points of those curves and chafe.
Speaking of pre-contouring flat steels, do note that curved steels are not the sign of an inferior garment. Cheap plastic bones will crumple like an accordion under stress. Flat steels will mirror the curves of the corset pattern and the body that wears it, and can intentionally be curved to do so. I like to contour the center front of my corsets to minimize pressure on the solar plexus and, well, guts, as well as the side-seams on my ribbon corsets to encourage the straight ribbon edges to curve rather than simply flare.
If you’re really curvy, you may be better off with spiral steels. Why? Well, as Ani DiFranco says, “What doesn’t bend, breaks.” Which isn’t to say flats don’t bend (since I just said they did), but they don’t bend as far or as comfortably as spirals. At Dark Garden, I just took a friend’s corset in to be repaired: two of the flat steels had snapped right on the waist line side seam. I showed our production manager and she said, “It looks to me like she’s really curvy. We should replace these with spirals, because those don’t break.” She was right, the friend is very curvy, even without her corset on, which she wears daily for an impressively rigorous schedule of work-related travel and personal activities, and though the spiral steel corset I’d made her two years ago has worn out in some places, the bones themselves remained true. Again, your mileage may vary according to personal taste and the source of the boning in question, but it is well worth considering.
Another instance in which spiral steels may be preferable is when the corset is intended for performing. Dancers and circus performers often need the extra mobility provided by spiral boning.
Waist trainers and tightlacers are another bunch that can go either way. It may be easier to cinch to smaller reductions with spirals (results may vary!), but they may also lack the feeling of constriction and confinement that some tightlacers not only enjoy, but crave.
What’s your preferred boning type and why? Share your opinions and experiences in the comments below!