Pink Brass and Lemi Shine


Lemi Shine has been questioned as a cleaning agent for brass because, in some circumstances, it seems to turn the brass pink.

But is it?

The issue is whether or not the Lemi Shine is damaging or somehow making the brass less suitable for use with ammunition. That is, has the brass been weakened, become brittle or suffered some other change that might make it dangerous to re-use as a result of exposure to Lemi Shine?

I decided to find out.

Normal cleaning advice is 1/2 teaspoon of Lemi Shine in a gallon of water along with several drops to as much as a tablespoon of Dawn dishwashing detergent.

Some then advocate a one hour “shake, soak, shake and soak” treatment before using a vibratory-style or ultrasonic cleaner. Those of us who use the wet tumbler method simply tumble in that solution for two to four hours. Regardless, it is at this point that the pinkish cast, if any, will be apparent. (The soaked brass is rinsed thoroughly in plain water before the cleaning process continues.)

Wanting to “get there sooner”, I increased the concentration: I used a full tablespoon of Lemi Shine (1 tbsp = 3 tsp) and only one quart of water (4 qts = 1 gallon). In effect, my solution has 48X more Lemi Shine than the recommended dilution. (I omitted the Dawn dishwashing detergent in the hope it was not a necessary ingredient for the “pinking” effect. [It was not.])

For the first test, I wanted to see what effect, if any, Lemi Shine appeared to have on good brass. I randomly selecting ten pieces of “fired many times” 45 ACP brass from my own collection.

In the picture on the left is one of those pieces of 45 ACP brass after 48 hours in the concentrated solution. All ten pieces in this sample had essentially the same appearance.

You can see for yourself there is no hint of discoloration with used but otherwise “good” brass.

I conclude that long exposure to high concentrations of Lemi Shine will not cause used or otherwise good brass to turn pink.

So, if the pink is not caused by the Lemi Shine, then where is the pink coming from and why does it show up only after cleaning in Lemi Shine?

Some comments by others suggested that the pink might be evidence of a process known as “dezincification”. This occurs when brass (or other metals alloyed with zinc — brass is copper alloyed with zinc) is exposed to acidic soil and weather conditions for an extended period. What happens is that the zinc is leached out of the brass, first to the surface and then into the soil. What’s left behind is plain, and much weaker, copper which appears red.

For the would-be metallurgist readers, there’s more on “Selective leaching” at Wikipedia.

To see this for myself, I went to the gun range and scrounged up some brass that had been sitting out a while. It looked almost black in the full Arizona midday sun. I collected up a dozen pieces of brass after using a magnet to cull the steel shells.

One of these range-pickups had visible red spots (copper) where the zinc had been leached out by the soil and weather. The middle picture is that piece “as found”. The only thing I did was gently wipe away the worst of the dirt so you could see the copper red spots better.

Also in the middle picture, note that while there are red spots, the rest of the shell is still brass-colored.

I then put the weathered brass picked up at the range into the concentrated Lemi Shine solution for eighteen hours. I then took the third picture you see here. This is the same piece of brass as in the middle — you can see that the red spots are in the same locations.

The overall “pinking” is now readily apparent. The red spots are redder and what was brass-colored before cleaning now appears pink after cleaning with Lemi Shine.

What we see in the third picture is large spots where the zinc has been completely removed — the red spots — and microscopic-sized areas all over the shell where this has also happened. That’s why the entire shell appears pink.

Why does the shell appears brass-colored before cleaning and pink afterwards?

I don’t know exactly. But I do know that in brass where dezincification is taking place (middle picture), the Lemi Shine makes this extremely obvious by making the entire shell look pink.

And where dezincification has not started, no pink appears. (The left-most picture.)

In summary, then, weathered brass shows pink under the influence of Lemi Shine whereas unweathered brass does not.

So, is the Lemi Shine damaging the brass or is it simply making a defect obvious?

I pretty sure it’s the latter: Just as Litmus paper turns red in the presence of acid, I think these shells are turning pink under the influence of Lemi Shine when they already have some degree of dezincification.

The brass is starting to come apart at the molecular level and the Lemi Shine, in cleaning the shell, is allowing the elemental copper — where dezincification has taken place — to be seen.

Since the Lemi Shine not only helps in the cleaning process but also makes dezincification visible, the Lemi Shine is a double-win. You get better cleaning and also an early indication of deteriorating brass.

Thank you, Lemi Shine!

You’ll find more details on my use of this product and where you can purchase it in “Wet Cleaning with Stainless Steel Media” on this blog.

(This article was edited on September 25, 2015 for clarity and to add the link to the Wikipedia article.)

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