As some of you know, I’ve recently begun to experiment with incorporating patinated and non-patinated metals (primarily copper) as decorative and smaller structural elements in my furniture pieces (wood is the primary medium). I have the Hughes & Rowe book on order; however, a more immediate concern is how to best protect against or slow down further tarnishing, once I’ve achieved the look I’m after. (BTW, the current pieces are for indoor use only.)
I’ve been searching on the web and have spoken to a couple of furnituremakers who work primarily in metal, and all seem to agree that copper is a particularly difficult metal to protect (too bad — I like the look!). Lacquer seems to be the most common finish used — some have suggested a “baking-on” process that I need to look into — but there also seem to be some general questions about durability, adhesion, etc.
What would you recommend for finishing copper? Durability and clarity are important, but I also realize that this may just be a finish that has to be maintained a bit more scrupulously. Compromises may be in order. If so, I’d like to make sure that clients are aware of these issues and prepared for them, upfront — I’d hate to get a nasty call a few years down the road because the piece that was meant to “last a lifetime” seems to have suffered the ravages of several eons.
Thanks,
David
“The world that was not made is not won by what is done” — Mundaka Upanishad
Replies
I actually spent time as a metalsmith working with copper and brass fabrication and we used paste wax for a line of copper lampshades. Tre wax or Butchers wax are fine. Lacquer is good also but more of a plastic looking coating. It helps to flatten it out a bit. Outdoors is a whole different matter. One should include instructions on how to care for the item as most people don't have a clue.
You should be looking at sites devoted to metal!
http://www.sculpt.com/
http://www.artmetal.com/w-agora/index.php3?bn=&site=techtalk
http://www.copper.org/
Edited 5/16/2003 12:13:57 PM ET by Rick at Arch. Timber and Millwork
You should be looking at sites devoted to metal!
Point taken. Actually, I have done a couple of days -- off and on -- of searching on the web, including both sculpt.com and artmetal.com, but apparently I haven't been putting in the right key words or been looking long enough. I figured, in the meantime, that it wouldn't hurt to post something here, assuming that somewhere, someone with mixed-media experience such as yours would offer some ideas. And you did! (And I'm still looking over those sites, by the way.)
More important, thanks for the tips... it sounds as if your experience with lacquer -- the dulling effect -- is exactly what I've noticed. In some cases, that's just perfect. On the other hand, trying to balance out potential adhesion problems with lacquer vs. the regular reapplication required of wax -- and thinking of what might be required of potential customers in terms of upkeep -- it sounds as if I'll need to weigh a number of issues before reaching a decision for each piece/client.
Thanks again,
David"The world that was not made is not won by what is done" -- Mundaka Upanishad
I have no idea whether the copper will continue to tarnish or not... and if so at what rate. What I can tell you is that acrylic seems to be the preferred resin for coating copper.
Sherwin Williams makes an acrylic lacquer that can be used directly over copper.
If you want more durability and especially better adhesion... PPG has a line of water-reducible metal cleaners and conditioners that work well. Looking at my PPG product data sheet book I see that they spec out brass and copper in the same section as aluminum that is to be clear coated. Which is good because most of the metal cleaning and conditioning materials will change the physical appearance of the metal due to the strength of the acids used. Aluminum that is to be painted gets treated with a different cleaner and conditioner than does Aluminum that is to be clear coated. PPG recommends the application of their acrylic urethane (catalyzed) DAU 75 after having finished the metal cleaning and conditioning steps on brass, copper, and aluminum that is to be clear coated. Now... it does mention that this particular cleaning and conditioning process can be used on aluminum to keep that bright silver look without a clear coat over it. But... I don't know if it would produce a similiar tarnish resistant coating on copper or not. I would at least test it out to see if it might not. If so... that'd give you more options in terms of the finished look of your furniture. Also, the DAU 75 can be flattened down using the specified PPG flattener. If you go this route your local PPG jobber should be able to suppy you with all of the relevant PPG data sheets which will spell out precisely what you need to do.
I hope this helps
Kevin
Thanks very much, Kevin. I'll check out the Sherwin Williams product, as it seems a bit easier to get my hands on. In the meantime, I've already gone over to the PPG site and am starting to get further information there.
Again, thanks for the tips. BTW, do you have any thoughts on how/where adding a patina should fit into the cleaning, conditioning and coating steps? I've been using the method Clay outlined on a different thread (burying the copper in salt-solution-soaked sawdust -- say that three times, quickly! -- for a couple of days), and am wondering if the patina might be completely reversed if it came before the cleaning and conditioning. In other words, the best order of events might be: cleaning, conditioning, patination and finally coating.
David"The world that was not made is not won by what is done" -- Mundaka Upanishad
Salt solution soaked sawdust... salt soaked solution sawdust... soaked salty sawdust solution...
;-)
David, I think you are spot on with your proposed order for cleaning and adding the patina. I doubt that the conditioning solution would affect the patina much. But, I'm certain that the cleaning solution would ruin it somehow. However... if my hunch is correct and the conditioning step would leave a protective surface film on the copper much as it does on aluminum... the patina may not take. You might try waiting until after the patina is on to do the conditioning step. I really don't know. Perhaps a metalurgist would be able to give you better feedback on the interaction between the copper, the weak phosphoric acid conditioning solution and the patina itself.
Interestingly enough... to me at least... not more than ten minutes after posting my earlier response I received a packet of data sheets for a variety of M.L. Campbell products from a salesman. They have a new product which may be the perfect solution to your particular set of needs.
The product is called KLEARPLAST V.O.C. STAY CLEAR WOOD FINISH. It's a new hybrid of acrylic lacquer and CAB (cellulose acetate butyrate) lacquer which is water clear (non-yellowing), has "excellent adhesion" and... this part surprised me as I read it... it can be applied over "brass and copper." If it performs as advertized... you could conceivably spray your entire piece of furniture... wood, copper and all, in one shot. They claim that it sands good and can be used as its own sealer too, which would be a time saver.
I'm considering stocking a gallon of this stuff for my own use because of it's interesting properties. Just yesterday I did a couple samples that were faux painted strawboard (same as MDF except uses wheat straw instead of wood fiber) that had decorative brushed aluminum strips down one side. I pulled the aluminum strips out and shot 'em with a DuPont automotive clear while the strawboard received a protective coat of McDonald photographic lacquer to protect the latex faux painting treatment. I could have shot the whole thing with this stuff and saved myself some time.
Keep an eye on M.L. Campbell. They've got some very interesting new products coming out.
Regards,
Kevin
Kevin, thanks again for the tips. Isn't it odd how things time themselves?
David"The world that was not made is not won by what is done" -- Mundaka Upanishad
This forum post is now archived. Commenting has been disabled