Shell forming is a dynamic, sculptural technique in metal fabrication that brings movement and dimension to flat sheet metal. Developed by renowned Finnish-American metalsmith Heikki Seppä and introduced in his influential book Form Emphasis for Metalsmiths (published nearly 40 years ago), this method allows artists to create flowing, organic shapes that mimic nature.
As Seppä describes, “The word shell means the outer skin of any form. The shell form is never solid. It begins as a flat shape, but through the shell-structuring technique, it evolves into a three-dimensional object and finally into a hollow structure.”
At its core, shell forming transforms hard metal into ethereal, curving forms. The result? Jewelry and sculpture that look alive, fluid, airy, and full of visual movement.
Inspired by Nature
Nature offers an endless archive of inspiration when it comes to shell-like structures: the smooth curve of an egg, the protective dome of a turtle’s back, the spiral of a snail, or the deeply grooved exterior of a walnut. These aren’t just biological marvels, they’re sculptural blueprints.
Shell forming allows metalsmiths to extract that same elegance and complexity from a sheet of metal. The process doesn’t just shape metal, it animates it. Pieces take on the illusion of softness, fluidity, even a sense of breath.
Mastering the Tools: Hard Meets Soft
One of the beautiful aspects of shell forming is how it leverages the relationship between hard and soft materials. Typically, you work with hard tools like steel stakes and mandrels in combination with softer forms like wood or nylon, or vice versa. This interplay gives you precise control over how the metal moves, stretches, compresses, and ultimately transforms.
You can even get creative with your tool setup, using hammers as stakes in a vise or carving custom forms from wood to suit your specific design needs. Once you understand how different materials behave and respond to force, you gain the freedom to push your work beyond basic techniques and into truly sculptural territory.
What Is a Spiculum?
One powerful application of shell forming is the spiculum, a tapered hollow form that originates from the Latin word spiculae. These forms offer incredible design possibilities: they allow you to create bold, voluminous shapes without adding heavy weight or requiring large amounts of precious metal.
Spiculums are perfect for statement cuffs, pendants, or neckpieces. They make a strong impression with less material, which means more creative freedom and less expense. The elegance lies in their simplicity and in the mastery required to pull them off seamlessly.
Synclastic and Anticlastic Forms
Shell forming also introduces you to synclastic and anticlastic forming, two advanced shaping methods that deal with how metal curves. Most of us are familiar with monoclastic forms which are single curved surfaces, only bending in one direction.
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Synclastic curves go in the same direction (like a bowl).
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Anticlastic curves go in opposite directions (like a saddle).
Mastering these forms can completely change how you approach design. You begin to see jewelry not just as adornment, but as architecture, delicate structures with tension, balance, and grace.
Why Shell Forming Matters
Shell forming invites you to leave behind the flat, the ordinary, the predictable. It challenges metalsmiths to craft pieces that are free, flowing, and alive, what Seppä called “forms that are inherently freer.” This philosophy resonates deeply with my approach at Ravena Metalworks, where I constantly seek to push boundaries and build from the raw energy of nature and personal memory.
From earrings that mimic the curl of a tendril to sculptural cuffs that feel like frozen waves, shell forming adds a level of sophistication and artistic vision that’s hard to match. It’s not just a technique, it’s a transformation, both for the metal and the maker.
Elevate Your Work
If you’re new to shell forming, consider it an invitation. Not just to try a new method, but to begin thinking about metal in a new way. As something responsive. As something alive.
And if you’re already a metalsmith looking to evolve your practice, shell forming opens the door to three-dimensional thinking, architectural structure, and an entirely new level of expressiveness.
Whether you’re making jewelry, vessels, or sculpture, shell forming lets you breathe life into your designs, pulling beauty from a flat sheet and turning it into something unforgettable.
