Coppering color

[Martes]

Something that puzzles me with the coppering of ship's bottoms - what actual color would it be and after how much time in water could it acquire this green hue?

 

[Bob Cleek]

The color looks a little "photo-shop-y intense" to me, but the answer is that the "time in water" doesn't make any difference at all. It is exposure to air, not water, that creates oxidation which adds the verdigris color (blue-green) to copper and copper-containing metals like brass or bronze. Acids and heat will contribute to oxidation as well, but not water. It actually happens pretty quickly. The copper oxide forms a patina that prevents further corrosion. The intensity of the color depends upon the nature of the copper alloy and how long the oxidation goes on. The bottom on the boat pictured looks like the water's movement at the waterline has scoured off some of the patina, which is why the upper copper looks darker and browner, and the lower copper near the waterline looks blue green. That's a not uncommon appearance with coppered bottoms. Most oxidized copper boat bottoms look just like an old penny you'd get in change at the grocery store. At a distance of fifty yards, it's often difficult to even notice that a bottom is coppered (coppered bottoms are rarely seen these days anyhow.) They look a lot like red-brown colored bottom paint because that's the natural color of copper oxide.

 

 

The Statue of Liberty never got her feet wet.

Edited March 20, 2019 by Bob Cleek

[Martes]

Thank you very much for the reply

 

So, if I understand correctly, the bottom of a coppered ship that is (relatively) constantly moving in water would appear brown-red, not green-blue?

 

[Sea Hoss]

Just to jump in, a newly coppered bottom can be artificially "aged" to look old with the application of easy to get household chemicals. Depending on what you want, it can be sort of bronze colored or more toward a greener look.

[Bob Cleek]

2 hours ago, Martes said:

Thank you very much for the reply

 

So, if I understand correctly, the bottom of a coppered ship that is (relatively) constantly moving in water would appear brown-red, not green-blue?

 

Yes, but only when it's under water in an airless environment. When it's hauled out into the air and the barnacles and seaweed are scrubbed off, it would probably be more accurately described as blotchy "brown-green." Copper deters marine borers, but it doesn't do much to keep vegetative growth at bay, so a coppered bottom hauled out after a period of time in the water will likely have a lot of crud growing on it. When that is scrubbed off, it will initially turn green very quickly as new verdigris develops on the abraded copper when exposed to air. That will thereafter turn to a "brown" penny color. Think of it exactly like a penny you found on the bottom of a swimming pool or somebody threw into a fish pond for good luck.

 

See: https://ussconstitutionmuseum.org/2016/11/18/new-copper-sheathing-2/

 

 

USS Constitution's coppered bottom hauled out for repairs. Green color a result of having been scrubbed (in this case, probably pressure-washed) and abrading previously oxidation. 

 

 

 

 

Note difference in colors of oxidation, perhaps from differences in plate alloys (e.g. plates wrapped around sternpost between above lowest gudgeon and the one above) and in other areas, perhaps due to intensity of pressure-washing. When she initially was hauled, she likely would have been pretty well covered with growth unless regularly scrubbed by divers while at the dock, which is also a distinct possibility.

 

 

Note above how very well scrubbed rudder which was brighter green in earlier picture above has, perhaps a few days later, already started to mellow to "penny" color.

 

 

Constitution being re-coppered. Copper tacked over (black) Irish felt underlayment. Original planking below that. Seams stopped with underwater seam compound. (Brown "stripes.")

 

 

Edited March 20, 2019 by Bob Cleek

[Martes]

1 hour ago, Sea Hoss said:

coppered bottom can be artificially "aged" to look old with the application of easy to get household chemicals.

 

Huh, it is a little simpler than that.

Since I am making 3d models that I want to look relatively natural within a computer game, it's all more or less about a color of a texture, and seeing the photos of Trincomalee in dock I began to doubt what actually it should be.

 

 

Edited March 20, 2019 by Martes