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Four different corsets, four different types of  steel boning
Four corsets, four different types of steel boning

Different structures require different raw materials and processes. The most obvious examples are boning channels that curve along the horizontal plane as well as vertically, which, of course, require spiral wires. In this case, that's the only sensible option in steel. But say you need to produce an historically accurate early Victorian corset; a wooden busk and cording (rope) may be appropriate.

Given the vast range of materials for stiffening corsets and stays that have been used in the past and are available presently, one article cannot give a fair and thorough assessment of the subject in full. So I have taken inspiration from corsets themselves (restrictive yet diverse garments) and pared my study down into a concentrated comparison between four variants on steel boning. Rather than attempting to produce each and every kind of corset, I will produce one corset with four different sets of steel.

By working within these restrictions, I hope to give each material a clear study so that you can decide which pieces of information are relevant and useful to you.


The Pattern

For this experiment I have adapted my basic standard sized underbust pattern, which peaks just below the bust on most figures and finishes on the high-hip. This allows for a lovely cinch, whatever the size, and should give our steels a chance to really assert their characteristics. I've adapted the pattern to a 29" waist to suit my models' proportions better.

By choosing a high hip we may also see if certain steels flex more easily without long expanses of body to “anchor” against (ie: whether the corset edge might dig in or sit smoothly, and whether this is affected by the steels used).

The Models

“Lady D” is of average build, just above average height, and is a very occasional corset-wearer.

She owns one bespoke Sparklewren corset and has modelled numerous samples for me so she is in a good position to comment on comparative comfort and ease of wear. Lady D has a lovely natural hourglass figure which is emphasised through corsetry, though she tends to lace off only around 3”.

Here she is in her bespoke overbust corset, which featured a combination of 7mm spiral and flat steels.

Lady D

“Lady E” has worn a couple of Sparklewren corsets, but has no other experience with corsetry. Her measurements are roughly similar to Lady D’s (a couple of inches larger through the torso), though their proportions and firmness differ.

Lady E tends to lace a touch more off her waist, but has a less dramatic natural waist/hip ratio than Lady D. You can see, looking at images of their early bespoke Sparklewren corsets, that they are both capable of maintaining the archetypal Victorian hourglass shape.

Here she is in her bespoke corset. Flats at front and back, with two spirals at every other seam.

 Lady E

By the end of this article, you’ll have heard both my opinions on the uses and practical implications of steel choices, and my models’ points of view on comfort, shape, and use of the resulting corsets.


A Bit of History

Flat steel boning has been in use since around 1840 (though not popularly until the 1860s), whilst some form of spirals may have been with us since 1820. "'Elastic' corsets were advertised in the 1820s, although this term seems to have meant corsets utilizing coiled metal wires and springs" (The Corset, A Cultural History, Valerie Steele, pp43). If any of the FR team or readers have a more accurate time-line for the production and use of steel boning in corsets I would be very grateful if you would comment below and improve our collective historical knowledge!

Bessemer steel converter
A "Bessemer Converter": part of the evolution of steel manufacture.

1858 saw Henry Bessemer create a process for steelmaking that modernised the industry, though “Plastic coating did not arrive until the first decades of the twentieth century” (Waisted Efforts, Robert Doyle,  pp123) and so rusting was a significant issue in what was then an everyday garment. Therefore, steel as a supporting structure was not, perhaps, quite as prevalent in the Victorian era as those new to corsetry assume. A corset was just as likely to use cording, baleen (whalebone), featherbone or even rubber. Since then, many technological innovations have taken place and the steel that we use now is treated and protected from rust and other damage. As an added bonus, though the use of raw materials mined from the earth might be of consideration to ethically-minded corsetieres or clients, steel seems to be a reasonably “green” option. “The steel industry has been actively recycling for more than 150 years, in large part because it is economically advantageous to do so...”  “recycling one ton of steel saves 1,100 kilograms of iron ore, 630 kilograms of coal, and 55 kilograms of limestone.” (Source)

So steel’s application in corsetry was certainly a product of the second Industrial Revolution, which also saw an explosion within visual culture as scientific possibilities caught the imagination of the masses. A “symbiotic relationship of fashion and advertising” (As Seen in Vogue: A Century of American Fashion, Daniel Delis Hill,  pp19.) was born that persists today, and it is perhaps this way of interpreting our visual culture (taking any given technological or artistic development and proclaiming it “the newest”, “the best” or “the most advanced”) that still causes so many heightened passions and disagreements within the world of corsetry!

We all have our preferred materials (you will discover mine by the end of this article) and are quick to defend them. But it is worth remembering that the development of corsetry-specific materials was not only in the pursuit of greater comfort, tighter waists, healthier waists, or improved garment longevity… it was also a way in which manufacturers of mass-produced garments could compete within the market as citizens became consumers.

Look at each new advertisement or patent: they are jam-packed with selling points and invariably discuss the “improvements” that the new design makes upon previous designs. Indeed, when I listed these samples for sale, I described the benefit of each design based upon the results that the different steel boning has. I used the observations made here to recommend certain corsets for athletic/firm builds and others for natural hourglasses.

Steel boning has, however, survived far longer and with more popular use than other methods of stiffening corsets. The result is that steel (in all its corsetry-specific forms) is arguably the most suitable way of supporting an average modern corset.

The Steels

We will work with four different types of steel: 5mm (3/16") and 7mm (¼") wide spiral steel, and 5.5mm (3/16") and 7.5mm (5/16") wide flat steel.

It is worth getting to know your materials in great depth. Yes, a 5mm spiral is obviously more flexible than a 7.5mm flat, but how different do the two types of spiral wire feel, when compared to one another? If you flex both widths of flat steel together, how do they feel in your hands? I’ve had some wider flat steels in the past that were flimsier than the 5.5mm flats due to their slighter thinness! So it’s worth trying different suppliers, experimenting with materials, and seeing what works best for you.

Try also imagining the steels en masse. What do you envisage happening when you have 30 or more 5mm spirals or 5.5mm flats flexing together? What are the different kinds of steel inclined to do when left to their own devices? Ie: what are their natural properties/tendencies, and how can we make the best use of them?

Flexing flat steels Flexing spiral steels
Two widths of flat steel, flexed. Two widths of spiral steel, flexed.


(Right) Held at one end, the different types of steel behave in very different ways.

How could this affect our four sample corsets?


The four different types of steels


Preparing the Bones

Each steel is individually cut to length. The spirals are finished using metal tips whilst the flats are filed smooth and dipped in tipping fluid.

I do advocate filing your steels to perfect smoothness, just to be safe. I am quite obsessed with filing my flats and like to ensure that I can press the end of the steel very firmly into my fingertip without there being any risk of broken skin. This reassures me that the steel won’t have any rough parts to snag or rub against the fabric, causing possible poke-through.

Bench grinder for rounding the ends of the flat steels Before and after filing

A bench-grinder and the 7.5mm flat steels: cut, paired, filed and dipped.

Two 7.5mm flat steels, before and after filing.



Testing the end Filing debris
 My flat steels need to be smooth enough to pose no risk of damage to either fabric or skin. A filed flat steel and the debris that can be created from a whole corset.


For these samples, I have dipped my flats into tipping fluid but you can also use PTFE (Teflon) tape to wrap the ends quite safely.

I usually pair my flat steels using a low tack masking tape that I label. Otherwise, things could get very confusing later on…

Bones paired and marked
  Whether flats or spirals, I cut my steels in pairs and label them for tipping/dipping later.


The Casings

The bone casings have been made using black satin coutil. For the wider steels, a 12mm (½") bias binder was used with straight-grain strips of the coutil. For the narrower steels, a 32mm (1¼”) strip of coutil was cut, and stitched/pressed as “tubes” before top-stitching into place. As a result of these two different methods, the narrower casings actually use more coutil to produce.

Each method, however, produces a strong and attractive exterior casing. If you are concerned about poke-through, it might be worth considering the second option as you can keep two layers of satin coutil to the outside of the steel. Alternatively, to be really resilient, one could always back the satin coutil with a regular herringbone coutil.


Boning casings - two different methods
There is little noticeable difference at this stage, but if you look closely you can see that the channels on the left are narrower and more numerous than those on the right.


Now, I’m sure you’re all aware that you need to stitch your casings/channels to have enough room to fit the steel easily but without the casing being loose. This is a very precise technique to develop but of the utmost importance.

I will note an extra tip though: when working with spirals rather than flats you can give the casing a little bit more room than you would usually (an extra 1mm (1/32") or so). Spirals are very flexible, and in some ways flimsy. Imagine a channel that is just slightly too snug… your flat steel, with a little persuasion, will slide through without difficulty. Your spiral, by comparison, will bend and buckle. Essentially, the pressure you are exerting downwards into the channel is being dispersed in other directions by the flexible shape of the spiral steels. So it is very important to stitch the channel with enough space.


The Other Fabrics and Notions

For fairness, each corset was produced using identical methods and materials (except for the casings, as already mentioned). Interior seams were flat-felled, each corset had a closed front, and the lacing panels at the back are in satin coutil with two-part Prym eyelets (4mm and 5mm (around 3/16") respectively). The strength layer is 100% cotton coutil, the fashion fabric is a silk dupioni and each corset has the all-important waist tape to support the seams. I have used different colours of silk, both to differentiate between the corsets and to provide a bright backdrop against which the placement of the casings and the overall silhouette will be clearly visible. I have also made one concession to received wisdom in that each corset features flat steels on either side of the grommets.


The Corsets

The Four corsets From top to bottom:

  • “Caribbean gold” (it’s green really) with 5.5mm flats,
  • “Bronzed Aqua” with 5mm spirals,
  • “Silver” with 7mm spirals,
  • “Peridot” with 7.5mm flats.

The corsets with narrow steels have 51 steels each, the other two have 44 steels each.


The Important Question of Quantity!

Due to the different thicknesses, I feel the fairest way to compare a real-life application of these types of steel is by saying that I have placed as many as possible on each corset, as this allows each different type/width of boning to really assert itself. As a result, the narrower steels clearly have a greater number of casings. This is, indeed, part of their “nature”… and one of the reasons why I personally enjoy working with narrower steels.

As a matter of personal preference, I also find a corset with a higher quantity of steels to be considerably more comfortable than one with only the bare minimum. This is amplified when the corset creates a large waist reduction. It’s all to do with pressure.

We know that a reduction on the waist puts pressure on that part of the body. Pressure is essentially the ratio of force over a given surface area. I’m afraid I wouldn’t know how to do the proper calculations, but if you take a waist of 30” (this is your the surface area) and then cinch it down to 26” (the corset is exerting the force) using a total of sixteen steels, then there is going to be a greater amount of pressure exerted per steel than if the same amount of force (the same reduction) is distributed evenly through forty steels.

The type of steel and its behaviour will also affect how pressure is spread. This is complicated by the fact that the fabric of the corset is actually applying the bulk of the pressure (it is the fabric rather than the steels that create the basic shape, after all), but do try it as an experiment for yourself and see if you can feel the difference.


RESULTS: 5.5mm flats, “Caribbean Gold”

Both Lady D and Lady E found this corset very comfortable. It sat smoothly on the hips and gave a pleasing shape whether laced with a 2” or 4” gap. 

Lady E stated that the corset felt very supportive. As she has a minor issue with her lower back (as so many of us do), I would never advise a corset as back support, but it is necessary to ensure that the client’s corset (even if only for very occasional wear) won’t cause additional discomfort or apply undue pressure. Lady E loved the feel of this corset and its sleek shape.

Front Back
 Lady D, by comparison, felt very supported but as though the pressure was evenly placed from the very top to the very bottom of the corset, as though it were almost “loose” around her waist. She said that she would rather the pressure was mostly at the waist, leaving her ribs and hips more free. As you can see in the images (right), D’s lacing gap is slightly above the 2” it should have been (she generally fits a standard 29” with ease). If we pulled the hip section any tighter, it resulted in more of a bulge at the hip as the steels pressed into her body. Front Back


RESULTS: "Peridot" cincher with 7.5mm flat steels throughout.

Again, Lady D was not able to quite achieve her usual waist reduction and even felt as though the corset was gapping at the waist. It wasn’t gapping, but the extra compression at ribs and hips made her imagine that it was.

You can see, especially in the back view, just how straight this corset was on her and that, once again, the hips could go no tighter without digging into her flesh. Again, I have to emphasise, each corset is made using the exact same pattern and same construction techniques. The only difference is the steel.

Front Back

Lady E really enjoyed the feel of the flat steels again and having a wider, firm ribcage means that the hug of the flat steels is very comfortable and flattering for her. Both women, however, noted that this corset (using steels with slightly less flex) dug into their hips a little more than the “Caribbean Gold”.

D noted that the straighter, flat-steeled corsets seemed more “casual” to her due to the reduced pressure on the waist; E agreed. Perhaps this would be a useful point to consider when building an “everyday” corset for a regular corset-wearer.

Front Back


RESULTS: "Bronzed Aqua" corset with 5mm spirals.


Now you should be able to see a clear difference emerging between the types of steel.

Lady D was able to achieve her usual wasp-waist silhouette and a much smaller and neater lacing gap (ie: greater waist reduction) than in either of the flat-steel corsets.

This suited her natural pear/hourglass shape better and she felt much more comfortable in the spirals. They followed her curves nicely around the entire corset.

Front Back

Lady E, by comparison, also achieved a beautifully wasp-waisted shape with the thin spirals and looked great, but felt less comfortable.

E has a slight sway back and almost seems to hold a straight-fronted posture when corseted (with the pelvis tipped back and the chest out), so it seemed that the increased curve, allowed by the spirals “collapsing” into her lower back, producing some discomfort.

It also pushed more excess flesh downwards so that she had “a mini-tire” beneath the corset. This wasn’t visible with her skirt, but is something to keep in consideration.

Both ladies found that this corset flowed onto their hips with ease and without pinching or digging at all.

Front Back


RESULTS: "Silver" corset with 7mm spirals

In comparison with the 5mm spirals (and in line with the 7.5mm flats corset), this cincher did pinch the hips slightly.

Each lady had a beautiful shape again, but lacing this corset to its finished measure was slightly tougher than with the 5mm spiral piece.

So we find ourselves considering pressure again...

Front Back

Does the greater number of bones help disperse the pressure of lacing more easily?

Is that why both the 7mm spirals and 7.5mm flats dig into the hips rather than curve over them gracefully?

Again, Lady E found this corset less comfortable than its flat-steeled counterpart.

Front Back



The FavoritesAfter the photoshoot, Lady D and Lady E declared that they each had favourites. Lady D loved the “Bronzed Aqua” cincher (with 5mm spirals) and Lady E adored the “Caribbean Gold” cincher (with 5.5mm flats).

Both ladies agreed that the higher number of steels created the most comfortable cinch, free from pinches and pressure-spots. I hope you can clearly see in the photographs how this also translates to a smoother line over the high hip.

We discussed body type for a while and considered how a person’s build and posture has such a huge effect on their requirements in corsetry. Lady E now knows that when she commissions work in the future she will be more comfortable in flat steels everywhere (except perhaps the side seams, if she feels like creating an hourglass silhouette from the front/back view, as in her crimson bespoke corset shown earlier). Lady D knows that her sense of self-image when corsetted (the wasp-waist and killer curves) is better achieved using spirals.

Comfort was the big issue for both ladies, as I feel it always should be. If your client is going to be spending a good amount of money on this luxury item, then it should be adapted to them in every way possible. Likewise, when producing free work for your friends in the early stages of your education, you want them to feel comfortable, glamorous and happy.

Testing the flex of the corsetsThey are your friends, after all! They’ll be so comfortable and thrilled with the whole process that they’ll merrily dance about and pose like fools in their corsets...

 They might just kill me for using this photograph (right)! But check out the amazing curve of Lady D’s 5mm spirals corset, and the smooth structure of Lady E’s 5.5mm flats corset…

Overall, I’m agreeing with my girls’ choices on this occasion. Both are wearing the samples with real elegance and ease, and each is flattered by their favourite corset. I also think that for this particular design, the greater number of casings is far more attractive as well as providing a better fit. It has certainly encouraged me to pursue this style a bit further.





It seems, on a very basic level, that spirals will follow the curves of a corset pattern more “immediately” than flats will. Flats will mould to the figure over time, but provide a smooth (rather than nipped) silhouette at first. This is worth considering if your client has specific needs from the corset. Will she only wear it once at her wedding? Or will she wear it once a week to go clubbing?! Does she have the time to “break it in”, or is the corset simply for a special occasion for which the fit, comfort and shape has to be perfect instantly?

For example, a bridal overbust corset for a soft and curvy client (with a rounded bustline and to be worn once) may have different requirements to a tightlacing underbust corset for a very slender and athletic client (to be worn 23/7 for an extended period of time).

Choosing the right type of steel for the body typeEven with a larger than ideal lacing gap this corset was comfortable and flattering on Lady E, and Lady D certainly had a bit of "Jessica Rabbit" going on. As a result of this experiment, I am now armed with more information on how best to corset these body types in the future.

As seen above, natural hourglasses and pears may benefit from the use of spiral steels more comprehensively throughout the corset, whilst athletic or firm/broad builds, or those with wide hips/ribcages, may prefer the smooth hug of flat steels through their entire corset.

It is very likely that many individuals will benefit from a combination of flat and spiral steels (as used often without question by commercial corset companies), but it is also worth noting that the strength and smoothness of the front of the corset (a place typically thought to require flat steels or a busk in order to maintain shape) was not compromised by the exclusive use of spirals.

7mm spirals cup the curves just rightI said at the beginning that you would discover my own preferences too!   Being a rather squashy natural hourglass I, along with Lady D, prefer the effect and feel of a corset supported throughout by spiral steels.

This is also emphasised by my lacing habits. I suppose I would be classed as an “occasional tightlacer” as I can easily reduce my waist by 6” (no doubt due to its generous starting size!) In order to do this, the excess must be displaced both above and below the waistline.

Most of my excess tends to move upwards which then means that the top of the corset must “open up” and “cup” those soft curves rather than press against them firmly.

The steels must sit almost loosely at the underbust point to ensure that they don’t interfere with my bra underwires. For these reasons, I prefer spirals in my personal corsets.  These 7mm spirals provided just the right amount of support for my body type though I would now consider using more of them! Flat steels either side of the grommets gave the necessary support for "occasional tight-lacing".


Results at a glance

  • A higher number of steels created the most comfortable cinch and smoothest line, free from pinches and pressure-spots.
  • Build and posture affect requirements and preferences: natural hourglasses and pears may benefit from the use of spiral steels more comprehensively throughout the corset, whilst athletic or firm/broad builds, or those with wide hips/ribcages, may prefer the smooth hug of flat steels through their entire corset.
  • The purpose and intended frequency of wear will also affect choices.
  • The strength and smoothness of the front of the corset (a place typically thought to require flat steels or a busk in order to maintain shape) was not compromised by the exclusive use of spirals.


Flaws in the Results?

The main flaw in this experiment (and also its main success) is the small range of options explored. What about low hiplines, overbusts, flat-fronted stays, Edwardian diagonals, cording, quilting, artificial whalebone, basket reed… What about accommodating prosthetics, transgender corseting, athletic builds, dancers and acrobats, plus-sizes, the very petite, and so on?!

It would take a lifetime to try out all the different permutations possible, so perhaps I can re-write the article in 50 years or so! Perhaps the next simple step would be to produce a fifth 29” sample cincher with the absolute bare minimum steel boning as a control piece by which to make further comparisons? 

I do know that a lot of you, however, will have much more anecdotal advice and experience than I have yet managed to accrue. Perhaps you’ve used 5mm spirals and hated them!  Perhaps you prefer 13mm flat steels, less boning overall, love hemp cording or are enamoured with artificial whalebone?

Please feel free to build upon this little experiment and share your thoughts in the comments section below. Many thanks for reading!

Great experiment, I hope many others will add their findings as time progresses.
I'm going to be looking into getting a carbon fibre boned shoulder brace styled corset with the help of a friend to hopefully improve my posture. Obviously, it's not recommended to everyone to just make their own brace! I am just thinking that I don't really have much to lose will a little experimentation ;)
This has been so incredibly helpful for me! Thank you for taking the time to document your research. You've saved me a lot of trouble in trying to decide which type of boning to use.
Thank you so much! I'm just getting into corset and costum making (amature) and this article was super helpful! I think I'm going to try spiral on the front and sides with flat at the back, since I'm quite curvy and my back tends to be slightly "sway-backed" (rather, I have an extra vertebrae which causes my pelvis to tilt out) as well. I want to accentuate the curves but also give my back enough support that the corset will be comfortable for a night out. I had assumed that wider steel would give more support, but that doesn't seem to be the case.
Thanks for the information.

This was really comprehensive! I always stayed away from spirals thinking they had too much movement in them not realizing they are probably exactly what I need for my figure! I have more than a 10 inch difference between my waist and hips, so using flats was probably ill-advised. Although, depending on the corset perhaps a mix of spirals and flats are needed?
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