Not sure what a spiral bone is?
Spiral bone is a flat and relatively narrow strip of steel wires that have been coiled together and flattened.
Spiral bones; one capped with a "U" tip and the other "dipped"
Spiral bones are commonly used in corset making, they add flexible support to the corset, and to the body wearing the corset. While corsets are what spiral bones were designed for (back in the 1900’s), they can be used anywhere that some flexible support is required…I’ve known them to be used in men’s doublets, ballet bodices, soft boots (up either side of the ankle), in the princess seams of contemporary ladies suits (well, that was back in the 90’s) and to make choker style jewelry.
So, how can a spiral bone be so versatile?
Spiral bones come is various widths and are sold both by the piece and by the yard/meter, which means you have choices. This article may help you understand how to choose the spiral boning you need.
The smallest spiral bone available (at least readily available) is 4mm wide which is about 3/16 of an inch.
4mm wide spiral bone with "U" tips
These are delicate and will not offer support to a body but will support smaller sized gowns; you can use them in the seams of the body of a gown to keep the lines of the gown smooth…the body wearing it will still need to wear a bra. You can also use them in corset making – place two, three or four side by side to get the support needed.
Two 4mm spiral bones in one bone casing (that was stitched down the center)
The most common size of spiral bone is 6mm or approximately 1/4 of an inch wide; the wires on these are a bit thicker than the wires of a 4mm spiral bone so they are more supportive and can be used in any corset where you want to enhance curves.
6mm Spiral Bones by the piece and by the yard/meter
A lesser known spiral bone size is 7mm which is also very close to ¼ of an inch wide but the 7mm wide spiral bones have a thicker wire than the 6mm size so while they are about the same width, the 7mm is more supportive than the 6mm. The 7mm spiral bones are sold only by the yard/meter.
There are also 11mm and 7/16 of an inch wide spiral bones and they are the most supportive spiral bones as the wires are thickest. The 11mm wide spiral bones at Farthingales are nickel free and are only available in pre-finished lengths. These larger bones are perfect for larger bodies as they offer more support and are more proportional to the body size.
There are "U" shaped tips available for all sizes of spiral bones; so if you cut the bones to the length you need, using the "U" tips to cap the cut ends to blunt them.
To see a video on how to cut and tip spiral bones click HERE
All spiral bones are flexible, they function much like whale bone stays used to in that they can flex in any direction. This means that they enhance curves rather than minimizing them. It also means they should not be used to support the grommets - if you lace the back of a corset and place these bones on either side of the grommets - the center back of your corset will become distorted as the bones are not strong enough for this purpose.
There is no perfect spiral bone size, it's a matter of which bone is right for your project. I suggest ordering a few bones of each size to keep as reference; then you can test the bones with each project and order those you want/need.