The standard gilding leaf is 23 carat gold. It comes in books of 25 leaves between pages of thin rouged paper. The leaf is 80-85mm square and approx 0.1 µm thick. A million sheets would be about 100mm (4 inches) high. It can vary slightly from one manufacturer to another in colour, thickness and surface texture.
Other metals have different characteristics and different colors and there is a range of different gold alloys available. The names and their color can vary from different manufacturers.
The leaf can't be handled directly because it sticks to the skin and tears easily. It is picked up with a gilders tip, a kind of flat brush of very soft squirrel hair. If it folds and wrinkles when the book is opened, you can blow the leaf flat by blowing directly down in the centre of the leaf.
Transfer leaf, also called patent leaf, is the same gold lightly pressed onto tissue or wax paper for easier handling. You can handle the leaf without needing a gilder's tip and it can be used in a breeze. It is only suitable for oil gilding.
Transfer leaf should be fresh, especially if it is on wax paper. If it is kept for a long time or in warm conditions, the gold adheres firmly to the paper making it difficult to use. Some transfer leaf is sometimes firmly pressed and takes on a matt texture. This applies to the tissue backing more than the wax paper. It can never give a really bright lustre. The opposite problem can occur too with the leaf almost falling off the paper backing resulting in wastage.
23ct The standard and most widely available gold
24ct is uncommon and usually reserved for exterior work where the absolute maximum life is required. It is more expensive than 23 ct, mainly due to manufacturing costs rather than the value of gold.
Red (23.5ct) has copper added for a beautiful warm color.
22ct is just slightly cheaper but the colour is generally like 23ct, perhaps just a little lighter if compared side by side.
Platinora Up to 23.75 carat. Gold alloyed with platinum, the color is slightly lighter than standard 23 carat
Moongold (20 - 23.75 carat) is alloyed with palladium and is a light brown/grey color similar to platinum.
18ct is a pale green/yellow combination of gold with silver and called either green or lemon gold. The gold/silver alloys were formerly known as Electrum
16ct is usually paler again and shares the names of green, lemon or pale lemon.
12ct is white gold (half gold/half silver) and is very pale. Still slightly yellow when compared with silver. It is the easier to work and preferred to the other white metals for this reason. Tarnishing isn't usually a problem but palladium can be substituted where this is an issue.
Silver is a clean cold light color, virtually a mirror when water gilded. It is thicker and harder to clean up than the gold alloys. Not used with oil gilding as it tarnishes to a brown.
Palladium is similar to silver in appearance. It is slightly darker than silver or 12ct but it doesn't tarnish.
Platinum is darker again than other white metals with a distinctly warm reddish tone. One of my favourites for its color but it's not easy to work with and is very hard to get.
Copper is a great color but very robust and almost impossible to clean up when water gilded. As a backing metal for glaze painting its color is fantastic. It comes in larger size leaves of around 140mm square as do the following common metals
Schlag (imitation or Dutch gold) is a brass with good golden color but like copper it is difficult to water gild and is not generally useful in glass work except perhaps as an oil gilded backing for large areas.
Variegated leaf comes several color types but all are based on either schlag or copper and are basically similar in their characteristics. The metal is heat treated to develop interference colors. They can be gaudy in large areas but have their uses. Very good as an interesting background when toned down with a glaze or antiquing finish
Aluminium has a cold milky blue tone and also may have manufacturing markings which mar its appearance. Best used as a non-tarnishing white metal background to a glazed treatment.
In Melbourne there are two manufacturers and some other imported brands. Wm. Ashcroft and Co. in Oakleigh produces hand beaten gold of consistent full rich warm gold color. The hand beating imparts a wonderful character to its surface texture. Weyermann in Frankston produces a more modern style, it is machine beaten in a cooler yellow (more brass like) color. It is slightly smaller in size (80mm) with an even surface texture and takes on an excellent burnish when water gilded.
I will also mention the vinyls that are used as a second class substitute. Most are dreadful tacky looking products that can't really be compared at all. The best product is SignGold which is a sandwich of 22 carat gold and vinyl. It is a vinyl product which has real gold as its colorant. It is a poly-vinyl flouride (tedlar) which is the most durable of the vinyl family as well as a very agressive and durable adhesive.