Anticlastic raising is a metalsmithing technique in which sheet metal is worked into a saddle or hyperbolic paraboloid form — a surface that curves simultaneously in two opposing directions along perpendicular axes. Where conventional raising produces concave or convex bowl-like shapes (termed synclastic forms), anticlastic raising produces the compound curvature characteristic of a horse's saddle, a Pringle, or the flared bell of a trumpet. The technique is achieved by selectively stretching the centre of a metal sheet while compressing its edges, or vice versa, using specialised stakes and hammers. Within studio jewellery, anticlastic raising is regarded as a foundational discipline for creating organic, architecturally complex forms that would be impossible to achieve by casting or simple bending alone.

Geometry and Mechanics

The distinction between synclastic and anticlastic curvature is mathematical before it is practical. A synclastic surface curves in the same direction along both principal axes — a sphere or a bowl being the canonical examples. An anticlastic surface curves in opposite directions: convex along one axis, concave along the other. This geometry, described mathematically as a surface with negative Gaussian curvature, is inherently resistant to flat-plane collapse, giving anticlastic forms a structural rigidity that belies the thinness of the metal used.

In practice, the metalsmith hammers sheet metal over a convex stake whose profile matches the intended curvature. Hammer blows directed along the length of the piece stretch the metal longitudinally, while the stake's curved surface simultaneously compresses the edges transversely. The interplay of these two forces — tension along one axis, compression along the other — drives the metal into its characteristic saddle form. Because the technique relies on controlled deformation of the metal's crystalline structure, work-hardening is a constant consideration; the piece must be annealed periodically to restore malleability.

Tools and Stakes

The stakes used in anticlastic raising are among the most specialised in the metalsmith's toolkit. They are typically narrow, elongated, and convex along their working surface, with profiles ranging from gentle curves suited to broad, open forms to tight radii for cuffs and rings. Stakes may be made from hardened steel, aluminium, or nylon; the choice of material affects both the surface finish imparted to the metal and the degree of rebound during hammering. Nylon and aluminium stakes are preferred when working with fine silver or gold, as they leave fewer surface marks and reduce the risk of unwanted texture.

Hammers used in anticlastic raising are similarly varied. A narrow, cross-peen hammer concentrates force along a line, ideal for initiating curvature, while a planishing hammer with a polished face is used in later stages to refine the surface and remove tool marks. Some smiths use a rawhide or nylon mallet for initial forming, reserving steel hammers for detail work. The sequence of tools employed — and the order in which they are introduced — is as much a matter of individual practice as of technical prescription.

Heikki Seppä and the Systematisation of the Technique

Although saddle forms have appeared in metalwork across many cultures and periods, the systematic codification of anticlastic raising as a teachable studio discipline is largely the achievement of the Finnish-American metalsmith and educator Heikki Seppä (1927–2011). Seppä emigrated to the United States and joined the faculty of Washington University in St. Louis, where he developed a rigorous vocabulary and pedagogical framework for the technique. His 1978 book Form Emphasis for Metalsmiths, published by Kent State University Press, remains the primary reference text in the field, articulating the geometric principles underlying anticlastic and synclastic forming and providing systematic instruction in stake selection, hammer sequence, and annealing practice.

Seppä's contribution was not merely technical. By grounding the technique in geometric theory — drawing on concepts from differential geometry and architectural surface design — he elevated anticlastic raising from a craft curiosity to a coherent design methodology. His students and their students have disseminated the approach through university metalsmithing programmes across North America, Europe, and beyond, making anticlastic raising a standard component of the contemporary studio jewellery curriculum.

Materials

Anticlastic raising is most commonly practised in fine silver (999), sterling silver (925), and the various karats of gold. Fine silver is particularly well suited to the technique because of its exceptional malleability and its tolerance for repeated annealing without significant surface oxidation. Copper and brass are widely used for practice and for finished work where cost is a consideration; both metals respond predictably to the forming process and anneal readily. Shakudō, shibuichi, and other Japanese alloys have been explored by contemporary smiths working in the tradition. Platinum and its alloys can be raised anticlastically but demand considerably greater force and more frequent annealing, and are less commonly used in studio contexts.

The gauge of sheet metal used varies with the intended form. Cuff bracelets are typically formed from sheet in the range of 18–22 gauge (approximately 0.75–1.0 mm), while smaller forms such as rings or pendants may use thinner stock. Heavier gauges are occasionally used for sculptural work where structural mass is a design element.

Applications in Jewellery

The forms achievable through anticlastic raising are immediately recognisable in the work of the studio jewellery movement from the 1970s onward: wide, flaring cuff bracelets with a dynamic, wing-like profile; collar necklaces with undulating edges; rings whose shanks swell and taper in three dimensions. The technique lends itself naturally to work that references organic forms — the curve of a leaf, the cross-section of a bone, the flare of a shell — without resorting to literal representation.

Because anticlastic forms are structurally self-reinforcing, they can be made from relatively thin sheet without sacrificing wearability. A cuff bracelet raised anticlastically from 0.8 mm fine silver will hold its shape under normal wear far better than a cuff bent from the same gauge in a simple arc. This structural efficiency is one reason the technique has found favour among jewellers interested in lightweight, wearable sculpture.

Anticlastic raising is also frequently combined with other metalsmithing techniques: chasing and repoussé to add surface texture; granulation or mokume-gane for decorative effect; stone setting within the raised form. The saddle geometry creates natural visual tension with the rectilinear facets of cut stones, a contrast that many contemporary jewellers exploit deliberately.

Teaching and Contemporary Practice

Anticlastic raising is taught in university metalsmithing programmes and at specialist craft schools including the Revere Academy of Jewelry Arts, Penland School of Crafts, and Haystack Mountain School of Crafts, among others. Workshops led by practitioners trained in the Seppä tradition are offered regularly through organisations such as the Society of North American Goldsmiths (SNAG). The technique has also been disseminated through video instruction, making it accessible to self-taught smiths working outside formal educational settings.

Contemporary practitioners continue to extend the vocabulary established by Seppä, exploring anticlastic forms in non-precious metals, in combination with fabricated or cast elements, and at scales ranging from intimate rings to large-format body ornament. The technique's geometric rigour and its capacity for expressive, sculptural results ensure its continued centrality in studio jewellery practice.

Further Reading

• Seppä, Heikki. Form Emphasis for Metalsmiths. Kent State University Press, 1978.
• Society of North American Goldsmiths: snagmetalsmith.org