Gold Leaf
Also: gold foil, leaf metal (gold)
Gold hammered or rolled into wafer-thin sheets, used in gilding, arts and crafts and food processing.
Gold leaf is produced by mechanical rolling or the traditional craft of goldbeating: a gold bar is first rolled into a fine strip, then extended between parchment or plastic layers in several thousand hammer blows into wafer-thin sheets. The result is foil with a thickness of typically 0.07 to 0.15 micrometres – thinner than a human skin cell. This is made possible by the extraordinary ductility of gold: of all metals it can be hammered and drawn the furthest without tearing.
Fineness and grades
Commercial gold leaf is offered in various carat grades:
| Designation | Carat | Fineness | Colour note |
|---|---|---|---|
| Genuine gold (transfer) | 23–24 kt | 958–999‰ | Deep yellow |
| Ducat gold | 23.5 kt | ~979‰ | Warm yellow |
| 22 carat | 22 kt | 916‰ | Slightly greenish |
| White gold leaf | 12–18 kt | 500–750‰ | Silvery white |
For food (confectionery, pralines, drinks) only gold leaf with the additive status E 175 is approved – at least 22 carat (916‰), nickel- and lead-free. The current gold price directly influences the material costs, as just a few grams yield a considerable area.
Manufacture: goldbeating
The traditional craft of goldbeating is divided into three phases:
- Pre-rolling – the bar is machine-rolled to approx. 0.1 mm strip thickness.
- Cutching – strip pieces are placed between skins (vellum, ox gut) and beaten by hand or machine to intermediate thickness.
- Fine beating – in a second packet the leaves are brought to the final thickness and cut to 80 × 80 mm format.
Area yield (approximation):
1 g Au × (1 / density 19.32 g/cm³) × (1 / thickness 0.00001 cm) ≈ 0.5 m²
(thickness 0.00001 cm = 0.1 µm, typical hand-beaten leaf)
Areas of application
- Gilding of picture frames, sculptures, church furnishings and architectural details
- Sign and book gilding (bookbinding, signs, glass gilding)
- Culinary – E 175 on pralines, in digestifs and on desserts
- Medicine/cosmetics – face masks, occasionally wound coverings (antimicrobial effect of low gold concentration)
- Electronics – ultra-thin contact coatings in special applications
A direct material value can be determined at any time with the gold calculator or the melt value calculator – relevant, for example, when buying gilded objects whose gold content is minimal.
Distinction: genuine gold vs. imitation
"Schlagmetal" or "imitation gold leaf" made of brass or copper-zinc alloys looks similar but tarnishes and is considerably cheaper. The distinction is made via the fineness stamp, or with loose leaves via the acid test or a gold testing device.
In brief
Gold leaf combines a millennia-old craft tradition with modern industrial application. Decisive for quality and price are fineness and thickness – both determine whether a leaf is suitable for fine gilding, food or technical purposes.