Opening-up is the bench-jewellery technique of scoring sheet metal along a line to create a controlled fold or hinge, producing crisp, accurate bends that would be difficult or impossible to achieve by simple bending alone. The jeweller uses a graver, scribe, parting tool, or specialist scoring knife to cut partway through the metal on the inside of the intended fold, weakening the material at that point so that the fold occurs along the score line rather than rolling across the surrounding metal. The technique is documented in standard goldsmithing references including Oppi Untracht's Jewelry Concepts and Technology and is used in box-making, hinge construction, architectural jewellery forms, and any work where a clean angular bend is required.

The technique

The basic procedure is sequential. The jeweller marks the fold line on the inside surface of the sheet metal — the surface that will face the inside of the bent form — and removes the metal along that line to a controlled depth, typically between one-third and two-thirds of the sheet thickness. The score should extend cleanly along the full length of the intended fold, with consistent depth and no breakthrough to the outside surface. A graver is the most common tool for the score; specialist scoring knives, parting tools on a lathe, or even controlled use of a rotary cutter are also used depending on the specific application.

Once scored, the sheet is bent along the score line using fingers, pliers, or a bending bar. The metal folds cleanly at the score, with the inside of the fold meeting itself in a sharp angle and the outside of the fold showing a smooth crisp edge. After folding, the inside of the score is generally soldered closed, both for structural integrity and to remove the visible score line. The completed fold is essentially identical in appearance to a fold-and-solder construction made from two separate pieces, but starts from a single piece of sheet, which simplifies positioning and alignment.

Score depth and material considerations

Score depth is the principal technical variable. Too shallow and the metal will not fold along the score, instead rolling across the surrounding sheet and producing a soft bend with a stress concentration that can crack later. Too deep and the metal can break at the score during folding, particularly with brittle materials like high-karat gold or work-hardened metal. The optimal depth depends on the material, the gauge of sheet, and the intended fold angle.

For 18-karat gold sheet at 0.8 millimetre gauge, a typical score for a 90-degree fold is approximately 0.4 millimetres deep, leaving 0.4 millimetres of solid metal at the outside of the fold. Sterling silver tolerates similar proportions; platinum requires slightly shallower scores because of its different mechanical properties. Annealing the sheet before scoring softens the metal and reduces the risk of cracking during the fold.

Applications

Box-making is the most common application of opening-up. A four-sided box can be constructed from a single sheet of metal scored along three lines, folded into shape, and soldered along the closing seam. The result is a box with three corners that are continuous metal (no solder seam) and one corner that is a soldered joint. Compared with constructing the box from five separate pieces of metal, the opening-up method dramatically simplifies positioning and alignment, and produces cleaner geometry at the unsoldered corners.

Hinge construction is the second major application. A hinge requires two interlocking metal forms with precisely matched cylindrical bores; constructing these by opening-up from sheet allows accurate alignment of the bores by scoring and folding rather than by drilling and assembling separate components. Architectural jewellery — geometric pendants, modular ring constructions, structural earrings — often relies on opening-up for the crisp angular forms that define the aesthetic.

The technique also features in repair and restoration work, where matching the geometry of an existing piece sometimes requires scoring and folding sheet to fit existing dimensions exactly.

Comparison with alternatives

Opening-up is one of several techniques for producing crisp folds in sheet metal. Alternatives include constructing the form from separate pieces and soldering the joints (more flexibility in geometry, more soldering required, more risk of misalignment), bending without scoring on a forming jig (faster, but produces a softer bend without the crisp inside angle), and electroforming or casting (entirely different fabrication paradigm, suitable for some forms but not others). For the specific goal of crisp angular folds in sheet, opening-up combines geometric precision with single-piece construction and is generally preferred where the geometry permits.

In the trade

Opening-up is part of the standard repertoire of any competent bench jeweller and is taught in most goldsmithing programmes as part of basic sheet-metal fabrication. The technique requires practice to develop the judgement of correct score depth and clean folding, but it does not require expensive equipment beyond a basic bench setup with gravers, files, and a soldering station. Apprenticeship-trained jewellers from the European workshop tradition typically learn the technique as a foundational skill; goldsmiths trained through self-study or short courses sometimes learn it later and are surprised by its effectiveness for crisp geometric construction.

See also scoring, folding, box construction, and the broader sheet-metal fabrication entries for related techniques.

Further reading

• GIA Gems & Gemology — bench jewellery technique articles
• International Gem Society — goldsmithing techniques
• Victoria and Albert Museum — historical goldsmithing reference