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Model Builders,

I am a new member but an old modeler. I am building a 1:76 scale model of the USS Constitution. Below the waterline, I have attached 1100 copper plates from Blue Jacket. Before I could coat them with a preservative, MANY of them turned dirty and/or greenish. I have tried to policy with copper polish, steel wool and vinegar, to no avail. Does anyone have a suggestion on how to restore just enough shine so I can preserve the brightness. I don't like the ocean salt green for a model.

Thank you for your participation.

best regards,

RG Head

Coronado, CA

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OK, it's sure choice, but I wouldn't want to have bright plating .... having said that, if your copper turns green, you have a serious corrossion problem somewhere. Green means copper sulfate or copper acetate, usually. You may have not done yourself (or rather the model) a good service by using vinegar (acetic acid) on the copper. If the green appeared before you applied the vinegar, you should investigate, where the sulfur/sulfate may be coming from before doing anything else. Or perhaps you cleaned the copper with vinegar before applying the plates and did not neutralise and rinse it properly ?

 

Normally, copper in a household atmosphere just becomes a dull copper-brown. At the seaside or in heavily polluted industrial areas this may be different, but Colorado is neither, I believe.

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I agree with wefalck that heavy corrosion on the copper plate should be investigated, and the cause identified and eliminated. No ship ever had a shiny copper bottom. The actual appearance of coppered bottoms has been discussed at length in other posts with many photos posted. Some modelers do still cling to "shiny bottoms," along with other stylistic affectations. Every artist presents their work to the world and the world decides whether it's worthy of appreciation or not. It's a chance we all take. It's your call to make.

 

If you want to remove the green patina, oxalic acid crystals dissolved in warm water (sold in paint stores as "wood bleach") will remove it effectively. (Wear rubber gloves, as prolonged skin exposure to the solution, particularly under the fingernails, can produce extremely painful skin injury. Don't ask me how I know this.) Alternately, there is a product marketed in hardware stores for cleaning bathroom fixtures and coffee makers called "CLR," (which stands for "Calcium-Lime-Rust") which is very effective in removing copper oxidation, as well.

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However, I would be rather hesitant to use any such chemicals on plates that are already on the model. It is impossible to prevent the solutions from creeping between the plates and there they may create havoc with the cement ... otherwise yes, oxalic acid is a good complexant for divalent ions, such as Cu(II), and will bring bring any CuSO4 into solution.

 

I gather you meant to use the descaler 'CLR' as an alternative to oxalic acid not alternating between the one and the other ?

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1 hour ago, wefalck said:

I gather you meant to use the descaler 'CLR' as an alternative to oxalic acid not alternating between the one and the other ?

Yes, exactly so! And I wouldn't advise cleaning a coffee maker with oxalic acid, either! :D

 

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32 minutes ago, Roger Pellett said:

Household Amonia fumes can be used to produce verdigris on copper.  Is it possible that your model became exposed to a cleaning product containing amonia?

 

Roger

I learn something new on this forum every day! Got to remember that one. Sometimes I want that patina without the wait.

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I am geochemist with many years of experience at the lab-bench ... on my work-bench there are no potentially corrosive chemicals, only paints and organic solvents (denatured alcohol, acetone, white spirit). When pickling or like processes are to be done, then away from the work-bench and near somewhere, where the parts can be thoroughly rinsed.

 

Never use any cleaning 'products' of unknown composition on a model itself. It will be very difficult to remove any residues and they may creep into joints etc., where they can create havoc over the years. On copper I only use fine steel-wool and acetone.

 

Don't use 'kitchen recipes' for patination etc. They may give more or less the desired effect, but it is important to create a stable patina that does not continue to eat into your metal or react with other components of your model. There are handbooks on patination/browning/blackening for metal workers, sculptors and the likes. Follow their procedures and recommended materials.

 

 

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