OT sort of
Paul Blackwell
Will a coat of poly keep copper bright and shiny? They are part of candle centerpieces I'm making for Christmas presents.
OT sort of
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#2Re: OT sort of
Ralph Lipeles
Paul,
To keep the shine you must prevent oxygen from getting to the copper. After cleaning the copper you must remove all traces of cleaner, dirt/grease transferred from your hands and any other contaminates. I wash the cleaned pieces with soap and water and then dry the pieces with paper towels. I then move the pieces, holding them with paper towels, to the area that I do spraying. Spray with clear lacquer and when dry, spray a second coat. After that you should be good for a lot of years.
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#3Re: OT sort of
John McGaw
As Ralph writes, cleanliness is key. I'll add that speed is important too -- clean the piece and, as quickly as possible, get an impermeable coating over it. I've been told that warm distilled water is the proper final rinse but can't verify that. Copper is notoriously reactive and is pretty indiscriminate about what it bonds with so you want to keep the rinse as pure and neutral as possible. Lacquer is the traditional shine-preserving coating and I'd think that most poly would be too thick to look right.
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#4Re: OT sort of
Bill Howatt
I've found for certain shapes such as thin cylinders that dipping in lacquer works well but either method should work. Cleanliness and total coverage is the important thing as mentioned.
Bill
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#5not an easy question
Bill Tindall, E.Tn.
This is not an easy question to answer. Traditionally nitrocellulose lacquer has been used to keep silver and brass bright. I suppose it would similarly keep copper bright. This thin polymer film is not a barrier to oxygen diffusion, yet it retards oxygen from reacting with brass or hydrogen sulfide from reacting with silver. I don't know how it works to keep these metals bright. Since I don't know how lacquer works I can't speculate whether a urethane varnish would be as effective. You can buy nitrocellulose lacquer in spay cans. I suggest using what has been shown to be effective for brass and silver.
The name "polyurethane" tell us the chemistry of how some components of the finishing product are chemically hooked together. The name does not offer a clue as to what is hooked together by "urethane" linkages, or what else is in the formulation that could affect it corrosion prevention. Some polyurethane varnish could be better or worse than lacquer, or a different polyurethane. No way to tell without testing.
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#6Use Lacquer
Tim Greif - West of Chicago
One of my hobbies used to be brass restoration. I've used nitro-lacquer, acrylic lacquer auto paint, ACE brand spray lacquer, spray poly and clear spray from Rustoleum and Krylon. I learned the techniques from an old gentleman in Iowa that did restoration for a living. He used a dipping tank full of what he called "bake hard enamel" that he bought in 35 gallon drums. He said it was the best thing he found to seal the metal and still be flexible enough to withstand dimensional changes as metal expands and contracts or flexes. He recommended I just use spray lacquer.
I found the Rustoleum spray clear would last about 2 years before it developed a "craze", essentially tiny cracks in the coating. My best success was with quality automotive acrylic lacquer which needed to be sprayed with either a detail gun or air brush. Kind of a pain for small jobs.
Next best was plain old ACE brand spray clear lacquer. Good performance and no "crazing". Others have mentioned cleaning of the metal. I concur. I simply cleaned everything with lacquer thinner and avoid touching any exposed part to avoid fingerprints.