Staining the floor with Manganese was not as straightforward as with Iron or Copper. The reward for sticking to it was a very nice color that reminds me of a hardwood floor. I started out trying to use Manganese Dioxide, but settled on Manganese Carbonate as a superior choice for this project. I made a separate page that explains the difficulties encountered while working out the recipe below.
This is a bag of Manganese Carbonate from the pottery store.
The color is reminiscent of face makeup but I wouldn't put it on my skin because the symptoms of Manganese poisoning are reportedly similar to Lead poisoning.
I tried to stain the floor using only manganese, but it didn't work out.
The addition of a small amount of Potassium (6) Dichromate totally fixed the problem.
Make sure to keep this stuff out of reach of children, hexavalent chromium can cause cancer.
A few years ago there was a movie called "Erin Brockovich" about a town that suffered when its water supply was contaminated with hexavalent chromium.
Below is a bag of bright orange Potassium Dichromate from a pottery store.
Since these ingredients are all so dangerous, you definitely want to wear gloves and eye protection while working with them.
Mix the dry ingredients together in a non-metal container.
Slowly add the acid, be careful not to let it foam up over the sides of the container.
This is like the volcano you made in grade school with the vinegar and baking soda except the acid is stronger, the base is toxic, and there is a carcinogen mixed in for good measure.
When the fizzing is done you'll have an almost black solution.
I brushed it out over 10 square feet of concrete.
The color of the freshly applied wet stain is so dark brown that it might as well be black.
When the solution dried, there was quite a bit of excess manganese powder left on the surface of the concrete. I mopped it up and the mop water looked like old used black motor oil. I accidentally spilled some of the mop water on clean concrete but it didn't leave any stain.
The photo below shows what it looked like after the excess was removed and the floor dried out.
It reminds me of "walnut" stain for wood.
The same area look much darker when it is wet:
I was surprised by how dark the floor was after being stained by the manganese. Especially when you consider how much excess black stuff was removed because it didn't soak into the concrete. I decided to mix up another batch with only one sixth the ingredients and spread it over the same 10 square foot area.
Again you want to wear gloves and eye protection and also use only a non-metal container. Mix the dry ingredients. Add the acid slowly so it doesn't foam over. Stirring with a non-metal spoon helps prevent a foam-over. I added the 1/4 cup of water just so that I would have enough liquid to spread it out over 10 square feet. I guess if you wanted an even more diluted look you could just add more water and spread it out over a larger area.
This diluted stain didn't appear nearly as dark as the first batch.
Of course that makes sense because 1/6th the manganese is spread over the same area, 10 square feet.
The image below illustrates the light brown appearance of the freshly applied "Lite" stain.
When this stain dried, there was much less un-absorbed manganese powder, although it was enough to blacken the mop water.
This is what it looked like dry, after the excess was mopped away:
And here is the same 10 square foot area while wet:
I'm not sure if anyone else would notice but I can see brush strokes in the "Lite" manganese stain. They are not visible in the image above but I can see them in person. The brush strokes were not detectable with any other stains that I tried except the Iron Chloride etching solution. Overall I think it is too minor to worry about and, in my opinion, the variation even enhances character. On the other hand I'm not sure how cute it would be if these were mop-sized lines instead of brushstrokes. Either way, it is very faint and I'm not sure anyone else would even notice.
I would like to see what you'd get if the "Lite" recipe was cut in half again. Also I'd like to try various mixes of manganese and iron stains. Finally I'd like to see if a good stain could be made from the Manganese Sulfate that is sold as fertilizer for palm trees.