Until the early part of the twentieth century, the only way to apply gold to a book cover was to use gold leaf. It is a painstaking and labor-intensive process. The invention of gold foil in 1932 changed all that.
The Good News
Gold foil was easy to work with and produced reliable results. For the first time, gold tooling could be mechanised. It revolutionised the titling of mass-market books, and has never been superseded. If you have a book with gold-colored lettering on your shelves right now, it was done using foil.
The Bad News
Although foil is easier to work with than leaf metal, it produces a less detailed result, and is rarely used in fine binding.
The Structure
Foil is made up of three very thin layers bonded together. It's much thicker than gold leaf on its own, and much easier to handle as a result.
---------------------- <- plastic membrane
---------------------- <- metal leaf
---------------------- <- adhesive
- Plastic Membrane
The plastic membrane gives the foil added tensile strength and cohesiveness. Without it, foil would tear and crumple almost as easily as gold leaf.
Because the membrane doesn't stick to the book during gold tooling, it is possible to design your tooled effect directly on it. It's best to use a stamp pad with water-soluble ink and a felt tip pen. That way, you can wipe off any mistakes with a damp cloth.
- Metal leaf
Originally, foil was made using real gold leaf. It was an obvious innovation to use other, less expensive metals such as aluminum and Dutch metal, as well as non-metallic colorants.
- Adhesive
The real innovation, the one that made foil revolutionary, was the adhesive used. Foil adhesive is a bit more sophisticated than glaire. It responds to a wider range of factors, namely:
Some kinds of foil are purely pressure-activated. These are used on heat-sensitive surfaces. Other, heat-activated foils are used in hot stamping processes as well as bookbinding. They respond to a variety of conditions, from very brief, very hot pressure to a long dwell with a relatively cool tool.
Foil adhesive will also stick to leathers treated with acrylic resin, which rejects glaire.
Foil is available from bookbinding and hot stamping suppliers.