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Lighting Products – Knowledge Base

METALS: All metals conduct electricity (thus the need for a “ground” wire).

  • Brass: Mixture of copper (55%-95%) and zinc and sometimes lead (for strength). May also have some lead, tin, nickel, etc. Yellow brass has 70% copper.
  • Bronze: Alloy of copper and tin (25%) and sometimes lead, zinc, phosphorous.
  • Copper: Usually plated because it’s too soft to hold shape (unless its fairly thick). Known for its ability to conduct electricity and heat.

Brass, bronze, copper, aluminum, and chrome do not rust and resist corrosion, so they are often used for outdoor lights. A green or brown patina forms over time and helps prevent corrosion. A magnet will not adhere to brass, bronze, or pot metal.

  • Chrome: Hard brittle gray metal used to plate other metals to give them a shiny finish.
  • Pewter: Alloy of tin (95%) and copper or antimony (sometimes aluminum is substituted which is very light in weight).

Pewter, copper, and pure silver dent easily.

  • Tin: Soft and easy to bend. Will rust. Often used in solder.
  • Tôle: Hand-painting on tin.
  • Silver: Softer than gold and usually plated onto a harder metal.  Sterling silver is not good for lamps because it’s too soft.
  • Wrought iron: Pure iron mixed with a glass-like material so it can be “wrought” into shapes.  (Cast iron is too brittle and cannot be shaped). Iron must be covered with paint or lacquer to prevent rust and corrosion.
  • Cast Aluminum: Light in weight, resists corrosion, silvery-white metal.
  • Stainless Steel: Resists corrosion and rust. 10% chromium.
  • “Pot” Metal: a gray alloy that can be cast but snaps when bent. Cheapest of all metals.

CRYSTAL & GLASS

  • Rock Crystal: Natural quartz mined in quarries. Very expensive!
  • Crystal: 24%-30% lead oxide (Lead improves clarity and softens glass for cutting).
  • Strass (Swarovski) Crystal: most expensive and most “fire”
  • Soda Ash Crystal (Turkish, Heirloom, etc.): Next best thing
  • Czechoslovakian: Some lead but not much.
  • Italian Crystal: No lead, just cut glass. Used in antique reproductions.
  • Murano Glass: Combination of quartz, soda, sand, potassium, and lead oxide at very high temperature. Glass is blown and stretched by hand. Many floral and unique shapes in glass.
  • Glass: Sand, soda, and lime heated in furnace and then blown, pressed (molded), or “drawn” (re-shaped).
  • Pressed Glass: Seams usually visible.

POTTERY & PORCELAIN

  • Porcelain: Hard paste ware fired at highest temperature. Purest and most delicate pottery.
  • Bone China: Hardest and most translucent of all porcelains.
  • China: Soft paste porcelain fired at lower temperature.
  • Stoneware: Clay fired to state of vitrification, non-porous, doesn’t require glaze for durability. Hard, heavy pottery that has a glossy surface when fired, so is often not glazed.
  • Earthenware: Clay that is not vitrified (glassy). Usually finished with colorful glazes and baked at low temperature. Very soft and easy to chip.
  • Terra cotta: (Burnt earth) Clay baked without a glaze, very porous and soft.
  • Bisque (Biscuit): Pottery fired once but not glazed.
  • Tin-glaze Pottery: Lead glaze made by adding tin oxide to glaze to conceal clay colors (Italian Majolica, French Faience, English Delftware).

OTHER MATERIALS:

  • Marble: Pressure and heat cause limestone to form into marble.  Pure marble is white. Pink and red marble has iron in it. Black marble comes from carbon or graphite.  Green marble is from chlorite. Tiny calcite crystals in marble make it sparkle. Marble can be cut or carved.
  • Alabaster: Alabaster is hydrated calcium sulfate which deteriorates when exposed to weather. High temperature will cause it to turn chalky white and then brown. Alabaster is carved, then sanded and smoothed, and then sprayed with polyurethane to close the pores and prevent deterioration. The translucent type is used for lighting fixtures lit from within (bowls and shades and wall uplights). The semi-transparent type (which resembles rock crystal) is used for lamp bases and lamp parts.
  • Wood:
    1. Hardwood: Walnut, Oak. Rosewood, Cherry, Maple
    2. Softwood: Pine, poplar, redwood
  • Wicker and Rattan:
    1. Wicker is usually made from willow branches and twigs.
    2. Rattan is made from reedy stems of palms in East India or Africa.
  • Hydrocal and plaster:
    1. Plaster: A lime, water, and sand composition that hardens when dry.
    2. Hydrocal: plaster with an extra bonding agent
    3. Cement: Sand, gravel, silica, gypsum, etc. added to plaster of paris mixture and fired in a kiln.
  • Resin (Plastic): Synthetic compound that can be dyed and molded. Stronger than hydrocal and non-porous.

CARE OF MATERIALS:

  • Brass & Bronze:
    1. Lacquered: Wash with sudsy water, rinse, dry, and buff with soft dry cloth. An old cotton sock makes an excellent polishing cloth,
    2. Not lacquered, shiny finish:  Wash and then apply brass polish.  Let polish dry. Then buff with a soft cloth. Apply thin coat of paste wax or lemon oil after polishing.
    3. For aged finishes:  Mix rottenstone and linseed oil to form a heavy cream and apply with a soft cloth and rub. Wipe off excess and polish with a soft cloth.
    4. For heavy corrosion: Rub with lemon dipped in hot vinegar, and salt mixture, wash, and rinse.
  • Chrome: Wipe with cloth soaked in sudsy water, rinse, and buff with a clean soft cloth.  For corrosion, rub with extra-fine steel wool.
  • Copper: Same as brass except use copper polish on unlacquered objects.
  • Iron: Wipe with a damp cloth and dry.  For corrosion, rub with kerosene and fine steel wool.
  • Silver: Follow instructions for brass except use a polish that is for silver only.
  • Silver-leaf and gold leaf: Use a soft shaving brush instead of a cloth to clean to avoid tearing the finish. To brighten, moisten a cotton ball with dry cleaning fluid or onion juice and gently pat (DO NOT RUB). Dry thoroughly.
  • Pewter: Polish with jeweler’s rouge and buff to produce a mirror-like surface. Pewter oxidizes slowly and evenly (as opposed to tarnishes) when exposed to air and gradually develops a soft warm patina.
  • Nickel: Polish with household ammonia.
  • Alabaster: Use a damp (not wet) cloth and gently wipe clean. NEVER use detergents or abrasives.
  • Marble: Remove stains with a paste made from hydrogen peroxide (from the drug store), powdered whiting (from the paint store), and a few drops of ammonia. Rinse with water, buff dry, and apply furniture polish.

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