Difference between red and brown copper toning?

What causes a copper coin to turn red? What causes one to turn brown? Are they caused by different chemical processes? Or is it the same process and brown has just been exposed to the necessary conditions longer? Like first yellow, red, purple, blue, brown, then black or something like that.

I've googled this one quite a bit and I always see conflicting statements (sometimes within the same article). Reading Coin Chemistry (Weimar) and even that seems a little contradictory. I believe it's saying various sulfurs in the air (hydrogen, carbonyl, and dimethyl) cause toning. It says keep your untoned copper coin AWAY from sulfur if you want it a nice red someday. Copper oxide is the nice red. Theres cupric oxide and cuprous, right? There's copper 1 and copper 2, right? One red and one is black. Is something other than sulfur making the copper red? It must be or he wouldn't say keep copper away from it. What's making the good red copper oxide? Does something other than sulfur create the good copper oxide?

So as you can see, I'm a jumbled mess. Seems that it's pretty well established that sulfur turns it brown. What turns it red? Well...I'd like to know. I guess I could go boil and egg and find out but that would be too easy

 

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Red is the bright shiny color when it is freshly minted. Brown is the color it tirns after a while. That's the difference!

 

It's not actually the color red.. It's just a numismatic term. Strange right?
Here is a chart for you

 

This would be a Red Cent.. No toning

 

I see. That's solved

 

Oh so that's how they turn red!

2 for 2!

 

Let's call red all the colors it will tone from mint fresh to before it is brown. Is it just a matter of different lengths of exposure to sulfur?

 

I have no clue..

 

Me neither!

 

Probably not sulfur.
Generally just oxygen.

Sulfur is the bane of silver.

 

It is any chemical that will combine metallically bound with copper. Some are more common than others in different environments. If it is in a sealed vacuum and/or anhydrous conditions, it will occur so slowly, the process will outlive even the youngest collector. IMO.

 

Paddy, Perhaps its my eyes, but the first red-brown ( left 2nd row) looks more red than the last in the the first row.

 

Sulfur is also the bane of copper, but the toning process is complex and involves oxygen and anything else that can oxidize the metal.

 

I'd like to know if that same process that turns the copper coin red (all the stages before it's considered brown) is what turns it brown. Is it just under those conditions longer? Or can a copper coin go right to brown?

And for the love of God, I know what the difference between red and brown copper looks like

 

There are copper cents that do actually turn a real red color. But all the ones I have seen were from environmental damage.
So maybe that's some of the confusion about "red" copper cents, which start out as red, but the color is not actually red.

 

It's like saying White Diamonds.. They are not actually white, they are clear. So a Red Cent is a brand new freshly minted look. Kind of like a golden copper color.