Part II: Landscape Lighting Manufacturing Processes
In Part I of this series I discussed some different metals and metal alloys used to manufacture landscape lighting. In Part II, I am going to discuss finish types, and the various ways to shape metals. There are many and is important to understand what you are getting when making your purchase.
Rolled, Stamped, and Spun
This process is the least expensive way to manufacture outdoor lighting fixtures. Thin flat sheets of metal are rolled, stamped and/or spun into a form. This is the least ideal way to form light fixtures as the original metal is typically of a low quality and since there is so little of it in the fixture it will be less durable, and more susceptible to breakage and cracking. This process is generally done with copper or brass light fixtures. Instead of buying cheap copper or brass (not to be confused with high quality copper or brass), you are better off going with cast aluminum with a good powder coating.
The most common manufacturing process is casting. The metal is melted and poured into a preformed die or “cast”. It is inexpensive and relatively easy to accomplish but you must be cautious when selecting fixtures that are made this way for a few reasons. For one, depending on the alloy there is an opportunity to use lots of different filler metals that can weaken the alloy and therefore the integrity of the fixture (see Part I).
Casting also leaves more opportunity for imperfections and porosity in the metal which can lead to pitting due to hairline cracks in the material. Manufacturers that import from overseas can have a difficult time managing the operations of the factories doing the casting, so often time quality control can leave something to be desired. Be sure that what you are purchasing is a high-quality metal with a very good finish. See Part I if you have any questions about what a good metal would be.
Of all the manufacturing processes for outdoor lighting, CNC (computer numerical control) Machined is the best. You may have heard CNC Machining referred to as milling and it’s a similar process but with the computer controlling the machine tools your end-product is much better.
Solid bar stock, which is a much higher grade of metal to begin with, is put into a CNC Machine that cuts away the bits that are not needed in the form. This is the most expensive process for manufacturing landscape lighting fixtures but will give you the strongest lights because the metal is so pure and there are no weaknesses. This process can be done with any of the most common metals used in landscape lighting.
Copper is a little more difficult to machine than Brass, Stainless Steel, or Aluminum because it is a softer metal. That makes the machining process a little more time consuming and expensive but it will leave you with a much more durable light fixture. If you want a fixture that is going to last a lifetime, I highly recommend looking into manufacturers that use this process to make their light fixtures.
After the fixtures have been shaped, some will have an additional finish applied over the metal. This is generally done to aluminum fixtures as the raw aluminum will not hold up in outdoor environments without some sort of protective layer (see Part 1). You can coat Brass and Copper but because those metals are better suited for the elements and because they beautify over time, there isn’t really any need to. So generally, copper and brass are just going to have raw finishes.
Powder coating is the most common form of protective layer. The process uses a finely ground mixture of pigment particles and resin powder paint that is electrostatically charged and sprayed onto electrically grounded fixtures and then baked. There are several different types of powder coats and some are better than others.
The main two used for landscape lighting are Epoxy and Polyester. Epoxy powder coating is very strong and impact resistant and provides very good adhesion. Unfortunately, UV rays from the sun can deteriorate and fade the paint layer leaving fixtures unattractive and more importantly, susceptible to moisture.
Polyester based powder coating is of higher quality and is very UV resistant. Depending on the resin type, it will withstand most US climates. There are many different grades of polyester powder coat. The resins and pigments are the two key component of powder coatings and will affect the longevity and durability of the finish, but fillers are also used to reduce cost and modify specific properties such as flow, surface texture, lubricity, etc.
Anodizing is an electrolytic passivation process that is used to increase the natural thickness of the oxide layer of the fixtures. This can either be done as a stand-alone process to finish the metal or as a step between the shaping of the metal and the application of a powder coat layer. Anodizing increases resistance to corrosion and provides better adhesion for paint. If you are using powder coated fixtures, make sure the product is anodized before the paint layer is applied. Otherwise the finish will deteriorate and the metal will oxidize and weaken over time.
A more unique finish type is a chemical acid treatment, sometimes called pickling. This finish is actually a chemical reaction between the acid and the metal, with a lacquer layer applied as a sealant. A paint coat is not needed because the acid weathers the fixture naturally. The acid finish not only protects, but beautifies the metal. Typically, an acid treatment is used in brass and copper fixtures and is an excellent option for coastal areas, as it will not corrode.
PVD Finishes (physical vapor deposition)
Physical Vapor Deposition (PVD) is a process that produces a metal vapor that is deposited on electrically conductive materials. The result is a thin, highly adhered, pure metal or alloy coating. The process is carried out in a vacuum chamber, at high vacuum, using a cathodic arc source.
PVD finish is commonly used for bathroom fixtures, exterior door knobs and other hardware that needs to be highly weather resistant. Because of this it works perfectly for landscape lighting. PVD finishes are salt resistant, scratch resistant, and water resistant, keeping the finish from altering for years- guaranteed not to patina in any outdoor environment. This is not a common finish type so it is a little bit more expensive.
The finish type and the grade of metal used will factor in to your fixture cost. Your lighting designer should know the benefits and drawbacks to all of these variables. This information is necessary to determine what manufacturer is best for your project. Nothing in landscape lighting is one-size-fits-all so be sure that your designer is informing you each step of the way. If you need help please feel free to call The Outdoor Lighting Guy 214-901-1197.