Gold was a goal of the Alchemists. It was used with power and style on the early hand powered fire engines. Lead, the starting element for the alchemist, also shows up in the paint on hand-tubs. The most waterproof paint for wood or metal in the 18th and 19th centuries was made from varnish mixed with white or red lead. This was the base for primers and many light colors on vehicles of all types.
Gold foil is beaten between sheets of vellum with heavy hammers on a stone table. The small sheet expands as it gets thinner. The gold is cut in quarters, re-stacked between vellum sheets and beaten until the foil becomes leaf. Hold a piece of leaf out in front of you, and it will droop down. Try the same with a foil (such as aluminum) and it will hold its own weight straight out. Most of the cost of gold leaf is the labor to make it. A leaf of gold, when crumpled up, turns to a speck. Small pieces, if picked up, melt into one's fingertips and vanish. Today's gold leaf is about half the thickness of 19th century leaf.
One gram of gold, the size of a grain on rice, can be beaten to make 136 leaves... so I've been told. It would cover an area 38 x 38 inches. All the gold ever mined would fit into three Olympic sized swimming pools. If all the gold at the core of this planet were brought to the surface, the gold on the earth would be 17 feet thick. There is a lot of gold, but it is hard to get.
A leaf of gold is 0.1 to 0.3 microns thick; 1 to 3 ten-thousandths of a millimeter; 5 to 15 millionths of an inch. A leaf can vary in size in different places around the world. Standard European and America leaf is about three and three-eights inches square. This dimension goes back to ancient Egypt, when a leaf was one Royal Palm per side. The measurement was the width of the Pharaoh's palm at the knuckles. The exact size varied with the size of each Pharaoh's hand.
Gold leaf is so thin that it must not be touched while being used. It is picked up with a brush (called a tip), a knife or sticks. Gold is usually mixed with other metals to make the leaf easier to work or to subtly change the color. 23 karat gold is 23/24ths gold and about 4% other metals. A lower karat gold can't be used outdoors or on a vehicle as it will tarnish. Karat is a percentage, used for purity of gold. Carat is a measure of weight, used for diamonds and other gems.
A book of gold, 25 leaves, cost 40 cents in 1860. By 1870 a book cost 60 cents. One leaf today, wholesale, costs more than a book back then. The price of gold leaf is mostly labor, not the gold. Still, the cost of gilding is mostly labor, not the gold. The process is slow and delicate.
If you don't have a fancy gilder's tip brush to pick up your gold, use a feather off your peacock. If you can't find your soft watercolor brush, to gather up the extraneous gold skewings, try the old-timers choice of a rabbit's foot or a squirrels tale.
I have seen engine turning on very few fire engines built before 1950. I keep expecting to see it on a parade hat or hand-tub, but it hasn't happened yet. Engine turning was a surface decoration in the 1800s used on safes, mechanical parts, portable steam engines and other unpainted metal surfaces. The sheet metal on Lindberg's Spirit of St. Louis was engine turned. The process makes a metal surface shine brighter as light reflects off tiny scratches. The method involves scratching a metal surface with a spinning wire brush or engraving tool. Gold leaf is so soft that the brush is replaced with velvet fabric.
19th century firefighters had torchlight parades in New York City. Engine gilding would catch the torch light and then reflect the dark night. When a person designs for gilding, one must plan for it to look black at times and then change to brighter than white.
Asphaltum has been used to tone gold leaf since the days of the ancient Egyptians and the Mayans. Back then it was found occurring naturally, bubbling to the surface of the earth. It still does, in places near the Dead Sea and the Labraya tar pits in California. Asphaltum is mixed with varnish and painted in a transparent layer over gold leaf. This gives the appearance of shadows and makes the flat gold seem to be three-dimensional.
Asphaltum was also used to waterproof metal. Tin ware was often given a coating of varnish with asphaltum to seal the tin. Colonial tole ware painting was often done on a ground of varnish with asphaltum and black. On hand powered and steam fire engines much of the iron work was painted with this same mixture of varnish, asphaltum and black pigment. The asphaltum made the coating tougher and helped prevent rust. Henry Ford's black Model T had asphaltum in the paint.
Asphaltum is painted on top of gold leaf to give the allusion of shadows. The pigment is mixed with clear varnish to make a transparent glaze. This can be painted on gold, red or green surfaces to create an instant shadow.
A brush is loaded with paint to make a single stroke on the gold surface. One edge of the brush holds clear varnish. The other edge contains dark asphaltum. The paint flows out as a transparent gradient, creating a blended shadow.
The cast shadow on the red surface is not a gradient. It is a mixed glaze of asphaltum and varnish. It is applied in calligraphic strokes, like the shade on sign-painted lettering. Some painters ran the cast shadow all along the gold stripes. Usually a thin line ran beside the gold stripe and the gold was outlined with black. Each ornamentor developed their own way of using the basic strokes, creating a wide variety of bold meandering scrolls on fire engines.
Most apparatus had more than just gold leaf reflecting light. Polished silver hardware was used on parade hose carriages, along with etched mirrors. The condenser dome on many steam fire engines was polished copper. The bronze pump fittings were also polished. Machined steel parts were nickel plated. Silver stripes and lettering were wanted by the decorative painters. Silver would tarnish quickly, so gilders used an alloy of gold and silver called "white gold". This metal has been used since ancient Egyptian times. The Egyptians called it Electrum and mined it already mixed thinking it was a separate metal. The pyramid at the top of obelisks were gilded with Electrum leaf.
Aluminum was a new product in the 1850s. It cost more than gold for a while. In 1857 aluminum cost $2.00 an ounce. Thirty years later is cost $10.00 a pound, and in 1893 it was down to 35 cents a pound.
Aluminum leaf was used on some steamers and motorized engines. Usually only for design accents, numbers and lettering.
For the Columbia Exhibition in 1893 the Studebaker Company built a wagon with all the metal parts made of exotic aluminum. It was an impractical sensation, made of rosewood with stripes of inlaid holly wood. Also inlaid into the body were 35 medals won by the company at other international events.
"Fire is the test of gold; adversity, of strong men."
Gold is not produced on earth. It is made when two neutron stars collide. Nuclear reactions occur, turning neutrons and protons into heavier nuclei stuff such as the elements silver, platinum and gold. The debris from the explosion become meteorites, and meteorites brought the metals to earth long ago.
Gold is the heaviest metal and the heaviest element. Gold has the highest ductility and highest malleability of any element. Its symbol in the chart of elements is Au which stands for Aurora, the Roman Goddess of the dawn. Gold does not tarnish or deteriorate like other materials. It seems eternal, untouched by time.