How I stained my concrete floor
Updated March 2007
I stained my entire first floor for about $5 using a safe lawn additive. Before I learned about this technique, I had been planning to use acid stain, which would have cost hundreds of dollars and required me to use some nasty stuff.
Photos
Summary of the process
Details
FAQs
Miscellaneous tips
Links and publications
The floor's color varies depending on the light. Below are several shots taken at different times during a sunny day in early spring. (The floor is a bit darker in the humid summer.) Click on a picture to see a larger image.
Here are some closer views.
Caveats:
- The colors might look a lot different on your monitor. The floor is basically tan with reddish brown variations and grey "veins." What might look like yellow on your monitor is light brown in real life.
- The colors get deeper as the air gets more humid. The floor is slightly pale in winter compared to its summer color.
- Your results could be quite different, depending on the age and type of concrete, strength of the sulfate mix, type of sealer, and who knows what else. Make several test spots.
I did the staining when the slab was six days old and exposed, before the walls went up. Briefly, I:
- Mixed one pound of iron sulfate into each gallon of water (a weak solution compared to other recipes)
- Wet the slab with the hose
- Mopped on a coat of stain, using random, rounded strokes as if applying a paint wash
- Let it dry (about 1.5 hours)
- Did two more coats the same way, wetting the slab before each one
- Let it sit overnight
- The next morning, hosed it thoroughly
I probably used about one pound of iron sulfate to do 640 square feet--I mixed four gallons and had most of it left.
The stain: iron sulfate
I read in strawbale publications that iron (ferrous) sulfate, also called copperas, stains concrete a reddish brown. I decided to get some and experiment.
Right away I learned the stuff must be more common in California and the Southwest, where supposedly you can get it at "any" nursery, even Wal-Mart. I finally found it at the farm bureau co-op, after the staff said they didn't have any. I had asked for iron sulfate, but the bag calls it copperas.
If in doubt, read the ingredients. Mine were
- 11% combined sulfur
- 19% iron
and nothing else. The brand was Hi-Yield. The co-op had only three 4-pound bags for $2.50 each, and I bought them all. It turns out I could have bought just one.
A young slab
On a Monday in November, the slab was poured, then scored to look like big tiles. The following Sunday, I stained it. I wanted to stain before the walls were up so I could use the hose for rinsing, and I thought the stain would take better before the concrete was fully cured.
Nature does the first staining
In the six days after the pour, oak leaves and acorns fell on the slab and were rained on. The leaves left subtle prints; the acorns left rust spots. Birds also made some contributions, and I had to pry off a dead skink. Overall, the slab took on a more natural, mottled look.
The slab dries after a rain. Some of the leaf prints remained after iron sulfate staining.
Two cleaning jobs
I did the first cleaning the day after the slab was poured and scored. The saw had left long piles of dust; I brushed, hosed, and scraped them off.
I did the second cleaning on Saturday, while I did test stains. The slab workers had left blue chalk lines and blotches. I had hoped the sun would bleach them but was out of luck. The only thing that got rid of them was Oxi-Clean powder.
For blue blotches, I applied a paste, let it sit about one minute, scrubbed, and rinsed well. For narrow lines, I mixed Oxi-Clean in a plastic container with some water and let it dry into rocks, scrubbed the line with a wet rock, then rinsed. Both techniques removed some concrete, leaving rough spots, but at least they weren't blue.
Before Oxi-Clean, I tried other approaches recommended on the helpful discussion board at Acid-Stain.com. None worked for my chalk, but they might work for your stains:
- 1 cup vinegar in 2 cups water; saturate, then rinse
- hydrogen peroxide, straight; let it sit, then rinse
- Carbona fabric stain remover
The blue chalk stained the concrete so well it would probably be a good colorant to make blue plaster.
Test stains: too intense
I had found only two stain recipes. Both have you create a saturated solution: you add iron sulfate to water until it doesn't dissolve anymore. In one recipe, you keep the solution stirred; in the other, you strain the solids or let them settle.
I put about half a gallon of water in a plastic bucket, poured in some iron sulfate powder, and stirred it with a piece of maple. Most of the powder dissolved, while some settled as grit on the bottom. I decided that was a saturated solution and started staining.
I made test patches under the future stairs. Keeping it stirred, I applied the stain with an old flannel pillowcase, using different approaches for each patch.
As the stain dried, it turned green-grey, then dusty orange. I wet the spot to simulate the effect of a wet-look sealer and saw a rich, reddish brown--too rich and too red. The color was more intense than I wanted.
If you like this color, you can get something like it with a saturated solution. Left of the line: one coat applied to dry concrete; right: two coats on wet concrete. The only part I liked is the brown trickle into the drain, and even that was a little strong.
Final stain: watered down
The next morning I mixed a much more dilute solution. According to a recipe from Matts Myhrman, 1.5 to 2 pounds of iron sulfate per gallon of water makes a saturated solution. I mixed just one pound per gallon. The liquid was a pale version of my test solution, and since I applied it to wet concrete, it got even more diluted.
Feeling brave, I wet the slab, then applied the stain, keeping the solution stirred. It turned out much closer to the color I wanted. So I put on two more coats, wetting the concrete before each one and checking the color after. I did all three coats in one long day, the last 50-degree day in November.
Tools and techniques
For each coat, I tried a different approach more out of desperation than artistic intent:
- "Wonder Mop"--a rag head mop that didn't squeeze out thoroughly enough, dripped, and was too hard to control. It left big swipes of stain.
- My tried and true pillowcase, swirled in two directions in each square. Fewer embarrassing swipes (or they just mixed in with the first ones) but a pain to use on 640 square feet.
- A standard sponge mop. I moved it lightly in small circles. This seemed to give the most consistent coverage.
I quickly learned to keep the bucket off the slab to avoid round stains, which I got even when I put an old sweater under the bucket. Since my boots would leave prints, I worked in two pairs of wet socks.
The stain looks just like water when it goes on--it takes awhile for the color to appear. When you're applying it to concrete that's already wet, it's hard to know if you're covering things completely.
I mixed four gallons of stain and still had most of it left after three applications. Dry concrete would have sucked up a lot more stain.
The next day I hosed the slab off thoroughly, though there wasn't much excess iron sulfate dust.
Nature gets another turn
The slab sat in the rain and snow for a week or two, collecting leaves and acorns again. When it was time for the walls to go up, we protected the floor with plastic topped by a layer of OSB. The slab is vulnerable until it's sealed.
Sealing
Once the concrete was inside and the weather had warmed up, I sealed the floor with the "wet look" masonry sealer from Seal-Krete.
It was easy to apply with a roller, gave off little odor, and dried to a matte finish. It intensified the colors of the floor, though not as much as water did. The result is a variegated light brown floor with some grey and copper "veins." People think it's stone.
I'm happy with the satin finish I got; it looks natural. Other sealers might have a glossier look. Probably all sealers affect the color somewhat, but a wet-look sealer makes the colors more intense.
The test area when dry.
The same area wet. It wasn't really this red. I gave up on trying to make my scanner get the color right. See the gray leaf stain?
The same area after sealing is less intense than the above photo but not as pale as the dry look.
Where can I get iron sulfate?
I used Hi-Yield brand iron sulfate, which they call copperas. If you can't find it locally, you can buy it from online garden supply and hardware stores. Search for "Hi-Yield copperas."
But isn't copperas a copper product?
"Copperas" is a common name for iron sulfate among American garden suppliers. Some art suppliers make the distinction between green copperas (iron sulfate) and blue copperas (copper sulfate). I've seen a site in the UK use "copperas" to mean copper sulfate, so be careful. The Hi-Yield copperas that I used contains only 11% combined sulfur and 19% iron--no copper or anything else.
What did you do to prepare the concrete?
I scrubbed off chalk marks and used a hose to rinse off the floor. I didn't buff the concrete or do anything like that.
How old was the concrete when you stained it?
It was 6 days old. I don't know how the stain would have been affected if the concrete were older.
Why did you stain the floor before you put up the house walls?
It seemed easier--I wanted to use the hose to rinse the floor.
How many coats of stain did you apply?
Three. You might try fewer if you want to see your application strokes more clearly or more if you want the strokes to blend more. If you use a stronger concentration, you might find one coat is enough. Make test patches.
Can I get a darker/lighter/different color?
You can get darker or lighter shades of reddish brown by using stronger or weaker concentrations of iron sulfate. You could also get a more intense color if you used the same dilute mix I used but you apply it to dry concrete. I wet the concrete first, which further diluted the mix and, I think, added "veins" where puddles overlapped.
I've also heard of several people who have added coffee to make a darker stain. If you want a greenish floor, you might try copper sulfate.
How far apart are the scored lines?
The lines make "tiles" that are 38" (96.5 cm) square. I made the lines run perpendicular to the walls for a peaceful, traditional look. You might consider diagonal lines for a more modern look, smaller or rectangular "tiles," etc.
How deep is the scoring in your floor?
The lines are cut about 1/4" (.5 cm) deep.
Won't the edges along the scores chip?
Yes. They've got lots of small chips. This just adds to the illusion of natural stone tiles. A machine-perfect edge would look odd.
Why didn't you fill the scored lines with caulk?
I like that the lines appear deep--it adds to the illusion of thick tiles. I also just prefer natural tiles to be laid without grout (I didn't use grout on the slate wall in the living room). I don't care that bits of visible debris sometimes end up in the scored lines--I just vacuum occasionally.
One drawback to open lines is they act like channels for spilled liquids. If you spill something in one spot, it will run along the lines to places you'd never think to check.
What sealer did you use?
I used a Seal-Krete product. At the time, it was called their "high solids" sealer. Now I think it's the masonry sealer they describe here.
Do I have to use a sealer? Can I just wax the floor?
The professionals at the Acid-Stain discussion board debate a bit over whether just waxing a concrete floor is enough. Some say you should seal, then optionally wax. You can't do the reverse and apply a sealer over wax. Seal-Krete makes non-toxic sealers.
Can I seal right after staining?
It's important to wait until the concrete has cured enough. If I remember right, the Seal-Krete sealer required the slab to be at least 30 days old. Be sure to follow your sealer's instructions. If you apply the sealer before the concrete is the right age, the sealer could fail dramatically and leave you with a nasty scraping job.
How has the sealer held up?
Four years later, some of the sealer is worn down. It's most noticeable in front of the sink, where I stand a lot. In other high-traffic areas, the sealer has lost some gloss. I plan to reseal the floor this summer. Every sealer needs to be redone at some point, but I suspect mine would have lasted longer if I had put down two coats originally. I may also wax the new sealer to get a longer life out of it.
Although the sealer shows general wear, it doesn't scratch easily. My Great Dane has monstrous claws, and we play fetch in the living room without worrying about the floor. Hard black plastic will leave a mark if it's dragged.
The sealer isn't completely waterproof. Water beads when first spilled but will seep through the sealer if it isn't wiped up in 5 minutes or so. This means I might stain the floor if I spilled coffee or something similar and didn't notice. A sick dog left no stain, but a sick cat did. The floor would probably be more waterproof if I had applied a second coat of sealer.
When I spill a little water when watering plants I don't bother wiping it up. I also don't worry much about rain coming in through open windows. If you like a low-maintenance floor, you've found it.
Has the color of the stain changed over time?
I don't think so. If the color has changed over the last four years, it's been so gradual that I haven't noticed it. The color does change temporarily with the relative humidity. As the air gets more humid, the floor gets darker.
Have you had any efflorescence?
No. The only strange marks that have appeared on the floor are small white spots below spider's webs. I can scrub them out.
Does the floor sweat on humid days?
The floor sweated a few times during its first two years. When the air temperature was in the 70s and the humidity was high, moisture would condense on the floor. This was clearly condensation, not rising moisture, because the floor was dry under my area rug. Only parts of the floor exposed to the humid air got wet, and only when other cool things, like the toilet tank, also sweated.
It happened mostly in spring and only when the dewpoint and air temperature were almost the same--for example, when the air temperature was 78 and the dewpoint was 76.
What would you do differently?
- Pay more attention to my strokes when applying the stain. Some of my less adept swipes are too visible.
- Apply two coats of sealer.
- Buy only one bag of iron sulfate.
Don't attempt this if you need a lot of control over the outcome.
If you're going to use a wet-look sealer, don't judge the color of the stain until you wet it. Other sealers might not affect the color so much, so be sure to test them as you go along so you know when to stop staining.
You might get very different results on older concrete, especially if it's been sealed.
Consider using a sprayer for more even coverage (strain the solution first).
Wear rubber gloves to avoid staining your hands, and wear old clothes.
Don't get the solution on glass (leaves a film) or wood (turns it grey).
You might smell rusty for a day or two.
While the sealer had little odor, it hung around subtly for a couple of weeks. If you have a sensitive nose, seal in warm weather so you can keep the windows open. It wasn't a toxic smell, just a slight odor of Elmer's glue.
A detailed description of how another homeowner stained his floors using a similar process.
"Staining Concrete Floors--My Experience" by Betty Wanck. In The Last Straw no. 31 (Fall 2000). How one woman stained several concrete floors. The most detailed info I found.
A one-page description of the process for stucco, by John Swearingen. Inspiring photos.
In the January 2003 issue of Fine Homebuilding (no. 152), one writer mentions that he used coffee to stain his concrete countertop. It looks great--mottled brown. He also used Scofield's Overlay to make a relatively thin, lighter weight countertop.
Discussion board on acid staining. Lots of info that could be useful for natural approaches.