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Preparing copper for patina finish
We are a small antique reproduction hardware and lighting manufacturer. One of our products is copper lanterns produced from sheet. All the parts are sheared, formed and soldered in our shop. We use an oxy/acetylene torch, silver bearing solder and zinc chloride paste flux. Currently to achieve one of our offered finishes, an even brown patina, we degrease the assembled lantern, then spend up to 45 minutes glass beading the entire surface on low pressure to remove finger prints, shop oils, flux and heat discoloration. Then the fixture is dipped in a cleaning solution called E-Kleen 154 before being submerged in the coloring agent B/OX 333. This process gives a nice uniform finish but takes a great deal of time, namely the glass bead operation. We've tried a stronger solution of the cleaning agent and reducing the glass bead time but the final finish is uneven. What I am hoping for is a chemical dip...copper etch?... that would safely and effectively remove all finger prints and flux while preparing the surface for coloring. Ideally I would like to not have to glass bead at all and am open to any suggestions regarding achieving an even patina finish on copper.Ron Hurd
Reproduction Hardware Mfg - Exton, Pennsylvania, USA
Try using a peroxide based Copper de oxidiser/ Surface brightener. Use the Metal finishing guide book.
The oxidider will clean and activate after the soak cleaning stage followed by a 2 rinse stage. Pre Sulfuric in 5% H2so4. Oxidise and brighten in the peroxide dip first for 2 to 6 minutes-. Post 2 % sulfuric. Rinse. Deionised Rinse. Go wet into the Patina - and see the diff.
- New Delhi, India