I wanted to make concrete pieces for the yard, but using standard gray concrete seemed a little dull. I have used the usual colorants with grey concrete and the resulting colors OK but muted. The "earth tones" were fine, but not what I was looking for. I had read that Latex Paint could be used to tint concrete, so I thought I would see what I could do. The finished products turned out pretty well; I have been doing this for several years now. I have made flower pots, table tops, a workbench top, pavers and various yard ornaments. The only downside that I have noticed is that the colors will fade when exposed to direct sunlight. I live in Arizona, so that may have some bearing on the fading.
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Step 1: Concrete Base Materials
This photo shows what I use to make the concrete base materials. I use standard bagged concrete mix to make the darker colors. Bright colors need a white base, so I use white mortar mixed with aggregate (rocks) to make white concrete.
- Standard bagged concrete
- White mortar (I use what ever is cheapest or on sale)
- Pea pebbles
Step 2: Colorants
These are the materials I use to color the concrete. I use the "charcoal" concrete tinting material along with black paint to get a very dark color with the standard grey bagged concrete. The other coloring materials are normal latex house paints. I have found the best paints to use have a lot of pigment in them, as the white mortar lightens the colors. I buy my paint from the "mis-tint" tables at the local big box store. We have a local Habistore that also sells cheap latex paint. Note that it MUST be latex based paint. I have used other paints and the concrete does not cure.
Step 3: Mixing the Concrete
I mix several colors at the same time. This allows you to cast different colors at the same time, giving you the opportunity to create a "marbleized" effect.
- Place pebbles into buckets first. This makes mixing easier.
- Add white mortar. 1:1 ratio of pebbles to mortar.
- Add liquid. 4 parts water to 1 part paint. Too much paint will weaken the final product. This ratio is for both the white mortar and standard bagged grey concrete. Do not make the finished mix too thin ("soupy"). A thin mix will be weak. I try to make the mix similar to a "mashed potatoes" consistency.
- Note the small plastic container - I use that as a measuring tool for the paint & water.
Step 4: Molds
There are lots of things that can be used as molds. I have used plastic flower pots, cardboard boxes, wooden forms that you can make, plastic storage containers, glass objects, styrofoam, etc. The smoother the material that you use, the smoother the final surface. Glass and plastic provide a very smooth finish that I have NOT had to sand, polish or work in any way.
What I am showing in the photo are glass lamp globes and some styrofoam packing material. The globes came from thrift shops (very cheap), and the styrofoam was wine bottle packing (free).
Step 5: Unmolding
The first thing to know about unmolding is to WAIT. Standard grey bagged concrete can be unmolded in one to three days. If I have tinted it with paint I usually wait at least a week. Using the white mortar, I always wait at least 2 weeks, sometimes longer (a month). Longer is better. Trust me, I have broken several pieces this way. I have planters, pavers and table tops that are several years old and are quite strong, but they DO need time for the initial cure.
Unmolding the glass globes is pretty easy, but messy. Just tap with a hammer and the glass will break away. Obviously you need to be careful of the glass shards. Gloves and glasses are always a GOOD idea.
The styrofoam is not too hard to unmold, just be patient. You CAN break thin/delicate parts of the concrete if you are too rough. Voice of experience again.
Step 6: FInished Products
This is a photo of the finished articles. I like the marbleized effect, and you can see how the white mortar makes the colors more pastel.
The cactus garden shows a couple of planters I made using tinted concrete.