How to Color Concrete for Crafts

Three families do this job. Oxides are where most people should start, because they are cheap, forgiving, and your set time and workability barely change from an uncolored batch. Natural minerals like mica and cobalt are the other earth-based route. Synthetics are the third family and they come with their own rules.

Look at the tubs and you can see the difference already. The oxides here are rated to 10 percent. The synthetics next to them are rated to 4.5. That number matters more than the color on the lid.

The max loading rate is a percentage of cement weight. Not sand, not water, not the whole batch. Cement.

This mix uses 200 grams of white Portland. The oxide is rated to 10 percent. That puts the ceiling at 20 grams of pigment, and the on-screen math is worth pausing on. Work your own number out before you open anything, because guessing here is how people end up with a piece that never fully cures.

Pigment goes into the water first, before it meets anything dry. Measure out your one part water, pour it onto the powder, and add your water reducer at the same time.

This is the step that decides whether your color comes out even or streaky. Dumping dry pigment into dry cement leaves you chasing pockets of concentrated color through the whole mix.

Pigment settles. Tip the cup, chase the corners, and keep going until the liquid is uniform and there is no grit sitting underneath.

Anything still down there will not disperse later. It shows up in the finished piece as a dark fleck.

Now combine it the way you normally would. The mix here is three parts sand, two parts cement, one part water, with a little water reducer.

That reducer earns its place on small castings. It loosens the mix so it flows into tight mold corners without you adding extra water, and extra water is what weakens concrete.

This batch used about half the maximum and landed on a soft sage. You have room to keep going up to your ceiling if you want it deeper and more saturated.

One thing to hold in your head while you judge it: wet concrete reads darker than cured concrete. What you are looking at will lighten. If it looks exactly right now, it will probably end up a shade paler than you wanted.

When the color you want is not in any single tub, mix. Yellow oxide and ultra blue at 10 grams each gives a yellow-leaning desert green. Shift the ratio to 75 percent blue and 25 percent yellow and the same two powders give you something mossy and muted instead.

Oxides stay earthy no matter how you combine them. That is the nature of the material, and it is why a genuinely vivid violet is not reachable this way.

Synthetics are what you reach for when you want saturation that oxides cannot reach. Purple is the obvious case, since violet barely exists in the natural pigment catalog.

The trade is a lower ceiling and a learning curve. This one maxes at 4.5 percent. Anything above a 1 percent loading rate needs considerably longer drying time, and blending it with an oxide helps stabilize the batch.

Efflorescence is the ashy film that turns up on concrete that has been in contact with water. Darker pieces show it worst, and anything living outdoors unsealed will get there eventually.

It comes off with a mild vinegar and water solution and a fair bit of scrubbing. Fine sandpaper handles whatever is left. Then seal with something rated for outdoors, which is what stops it coming back in the first place.