One of the challenges of bronze is explaining how its long-term, ever-changing beauty is due to patination—a process that naturally turns the surface varying shades of blue, green, and dark brown over time. It is this very process that draws tourists to the beautiful roofs of Europe’s cathedrals and other landmark buildings and sculptures. Over time the elements interact with the copper component to produce red‑brown cuprous oxide, dark brown‑black copper sulphide, or blue‑green copper carbonate. The patinas that occur during this oxidation process are on the surface of the bronze and they seal and protect the piece, adding to its structural durability by creating a living, changing patina.
The purpose of this post is to balance the pros and cons of how best to keep the bronze in its natural golden state and how different sealants protect bronze hardware.
Emile Meunier’s Cheval
Sealant Options for Natural Brushed Bronze
A sealant is a coating that helps prevent oxygen and moisture from reacting with copper and other alloys present in bronze. They range from simple waxes to clear powder coating, to baked enamel and acrylic and polyurethane lacquers. They vary in how they are applied, how hard they are, how easy they are to clean, and how difficult they are to repair if the surface coating is damaged. As a generalization, harder sealants like powder coating deliver a tougher coating that requires little maintenance, but if damaged cannot be repaired easily on site.
Powder Coating Clear
When we powder‑coat bronze our door handles and cabinet pulls, we use a UV‑stable polyester powder which is sprayed onto the bronze. The spray gun has an electrode that gives the powder a positive electrostatic charge and as the bronze is grounded through a copper conductive cable, the charged powder clings to the bronze. Once heated, the powder becomes chemically cross‑linked to create a uniform, very tough layer that bonds to the bronze surface.
Powder coating is an excellent finish choice for luxury exterior hardware particularly where salt air is present. It offers a good level of resistance to many chemicals and the effects of UV. It also does not require frequent maintenance and dirt and grease are easily removed with a soft cloth and pH‑neutral soapy water. The main drawback is the thickness of the coating, which tends to soften edges and, in the case of our luxury bronze door handles, can detract from the hardware’s design appeal. It also gives the piece a more plastic appearance and one that feels less tactile than simpler waxed finishes.
Clear Lacquer Sealants
These come in three forms—polyurethane, polyester, and acrylic—and are applied by spraying the bronze and then allowing the surface to cure either by evaporation or by baking.
They differ in their curing methods, toughness, and ability to resist degradation through exposure to sea salt and chemicals. Of the three, a 2K polyurethane spray offers the toughest finish and, like powder coating, it chemically cross‑links with itself to form a tough coat. Acrylic lacquers offer a reasonable option for outdoor applications and, like 2K polyurethane finishes, have the advantage that they can be refinished on site. Baked liquid polyester offers a tougher surface than acrylic lacquers but, as it is a baked‑on finish, cannot be refinished on site and must be returned to the supplier for re‑coating.
Mother Nature and the Old‑School Oil Rubbed Finish
We offer oil‑rubbed light and dark finishes for most of hand-crafted hardware by immersing the piece in an acidic solution followed by immersion into a neutralizing solution. The bronze will still continue to oxidize, so to slow the process down we apply a coat of microcrystalline wax made from very fine, tightly packed, pliable, high‑oil wax derived from refined petrochemicals or plant‑based carnauba wax. Regular maintenance will preserve the finish and dirt can be removed simply with a soft cloth and, if needed, pH‑neutral soapy water always applied with a soft non‑abrasive cloth. The wax can be reapplied as needed and should be included in the maintenance protocol.
Keyed adhesion
In all methods when the finish is liquid it will adhere and penetrate the surface where there are any pin holes and cling to slightly roughened areas, this is not a chemical cross linking but rather describes another way the finish adheres to the surface.
The Cleaner
The mystery began when our Ergo Wave custom bronze cabinet pulls developed unexpected red-brown stains several months after completion.
These luxury bronze hardware pieces were left in a brushed natural bronze and sealed with an acrylic lacquer finish—a coating that, once cured, is hard and moisture-resistant but never completely solvent-proof.
Photographs taken by the designer documented the hardware in pristine condition at pickup, delivery, and installation.
Yet weeks after the homeowner moved in, stains appeared on nearly every pull—and always in the same location.
Our best theory is that the housekeeper’s regular cleaning routine introduced the culprit.
A household cleaner with either an acidic or alkaline formula may have been sprayed directly on the pulls.
Even though the lacquer had fully cured, repeated contact with a cleaner such as vinegar, lemon-based sprays, or ammonia solutions (like typical glass cleaners) can micro-pit or etch the acrylic film.
We suspect that after spraying, the pulls were not thoroughly dried, allowing cleaner to pool along the back top edge where the pull meets the drawer front.
This residue gradually breached the lacquer, exposing the bronze beneath.
Once exposed, the copper content in bronze reacted with ambient moisture and oxygen, forming a cuprous oxide layer that appeared as a powdery red-brown stain.
The pulls have since been carefully re-buffed to remove the oxide and will be re-finished with a UV-resistant polyester powder coat for greater chemical durability.
Advice for Owners & Designers
Even the best protective finishes are not indestructible.
Whether it’s acrylic lacquer, clear powder coat, or baked enamel, any surface seal can fail if scratched, chipped, or repeatedly exposed to harsh cleaners.
Once the barrier is compromised, moisture, oxygen, and cleaning agents accelerate oxidation and the discoloration will spread.
Recommended bronze cabinet pull care:
Use a soft microfiber cloth for routine cleaning of luxury bronze hardware.
If needed, wipe with pH-neutral, lightly soapy water only. Do not spray.
Rinse and dry thoroughly—do not allow moisture or cleaner to pool.
Inspect hardware periodically and touch up or re-coat at the first sign of wear.
Following these steps will protect both the acrylic lacquer finish and the natural bronze beneath, ensuring your custom bronze cabinet pulls retain their beauty and warm patina for years to come.