Treatments
for the Coloring and Patinization of Bronze
By Tony Grieco
When it comes to durability and appearance over time, bronze
is the clear winner. This is why the best designers and specifiers
select these metals in their landscape lighting projects. While the
untreated surface of bronze ages beautifully to a patina or verdi,
there are occasions when either a different color fixture is needed
or when the patina color is desired immediately upon installation.
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There are numerous formulas
and treatments used to achieve these color changes. Many of
them involve the use of dangerous chemicals and extremely
time consuming procedures. For this reason, we spent a full
year talking to the experts and experimenting with their suggested
techniques.
The fruit of these efforts are the recommendations
detailed below. They involve relatively simple formulas with
ingredients readily available. We are confident that the two
treatments - one for patina, the other for black - will yield
the desired results of color changes that are easily accomplished,
long lasting and suited to the outdoor environment. |
Precautions
It is important to note before we go any further, that anytime you
are working with chemicals (no matter how safe) that you should
take precautions.
- Wear rubber gloves
- Use eye protection
- Work in a well ventilated area
- Do not allow children in work area
- Store chemicals in a clean dry area out of reach of children
- Thoroughly clean all containers and work areas before and after
use
- If you are spraying installed fixtures, cover surrounding plant
material with plastic
Patina – Greenish-Blue
While "patina" refers to any age-induced
color changes, it is the word commonly used to describe the
greenish-blue copper sulfate oxide created when bronze and
copper naturally age.
These metals will naturally patina over time, but the following
treatment is instantaneous. This is frequently desired by
the homeowner.
Formula
- 8 oz Ammonia
- 8 oz White Vinegar
- 1/8 cup Salt (use of rock or kosher salt may result in
different colors - experiment)
- 1 teaspoon Spreader/Sticker
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Procedure
- Out-of-the-box fixtures require no pre-cleaning. If the
fixtures have been outdoors for some time, you should remove
dirt and bird droppings with a cloth, steel wool or a wire
brush.
- Fixtures that have already been installed and undergone
color changes can be treated. If the surface of the fixture
has gone to old-penny brown, further treatment may result
in a darker color (compared to treating the fixture out-of-the-box).
If the fixture is in the chalky-white stage, then this whitish
coating should be removed with CLR prior to treating.
- Add the ingredients to a small hand or pump sprayer, in
the order as listed above. Make certain the ingredients
are completely dissolved and mixed well.
- Use a fine mist to apply the mixture to the light fixture.
Do not soak the fixture as this will create runs and pooling
of the mixture and delay drying. The reaction (patina) will
happen very quickly and allow you to see where you may have
missed and apply additional coats for even coverage.
- Allow the fixture to dry before handling or apply the
mixture with the light fixture already in place. If spraying
around plants, make certain to protect them from the spray
since both formulas can burn like a highly concentrated
fertilizer.
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Black
Formula
- 8 oz Ammonia
- 1/8 cup Liver of Sulfur (if needed, crush with mortar
and pestle to a uniform powder)
- 1 teaspoon Spreader/Sticker
Procedure
Use the same procedure as with the Patina.
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Brown
Formula
- 8 oz Water
- 1 teaspoon Liver of Sulfur (if needed, crush with mortar and pestle
to a uniform powder)
- 1 teaspoon Spreader/Sticker
Procedure
Use the same procedure as with the Patina.
Note
This formula turns bronze a nice dark brown, but does not work
well with copper (very streaky). For this reason, do not use on
fixtures with copper stems or shrouds.
Notes
To ensure that the homeowner will be satisfied with the final appearance,
you may want to show him/her a fixture already treated.
Coloring the fixtures will not affect CAST's warranty, but the fixtures
can not be returned because you don't like the coloring.
Materials
About the Author
Tony Grieco is CAST's Western District Sales Manager. |
