The concrete creation process can be broken up into three important phases. First is form construction, next mixing and pouring, and last is surface finishing. Although all three phases are important the form construction phase is critical and careful considerationshould be undertaken. I will explain the process used to create what I call the butterfly bench.

I used one quarter inch masonite strips for the sides of the form. The masonite bends easily and for tight curves such as the smaller end of this bench the masonite can be soaked in water and bent slowly. By tightening the rope every ten or fifteen minutes for an hour or so the masonite was able to be wrapped around a semi circle with less than a ten inch diameter. Diameters shorter than 6 inches could be achieved.

This piece is poured "upside-down". The butterfly mosaic is laid face down on the base and when the piece is flipped over after it has set the bottom becomes the top. I used MDF particle board for the base of the form which has
a smooth finish and is reflected in the top of the piece. Oftentimes a MDF sheet with a melamine coating is used. The melamine is a plastic which water does not permeate and allows for an excellent smooth finish. Next I caulk all the seems between the base and the masonite strips. This prevents water leakage and ensures the mix sets correctly.

To begin the mosaic I draw an outline. Remember that since it is "upside-down" when turned over the mosaic is transposed.
Small greenish stones were cut with a tile saw and used for the body of the butterfly. I apply a very thin layer of caulk to the surface of the stones and the broken tile. This seals them to the base so that the mosaic is even with the surrounding concrete. It also prevents small movements when the concrete is poured. Care is taken not to use too much caulk because this results in the mosaic being slightly below the finished concrete layer. Finally I caulked two small
strips of copper wire to the base for the butterfly's antenna. Now wait twenty-four hours for the caulk to fully set and dry before pouring
the concrete.

Rebar or wire mesh should be used for reinforcement. Take care to place it in the middle of the piece. If the metal is too close to the surface then "ghosting" can occur. "Ghosting" is a faint image of the metal in the surface.

The concrete mix used in the butterfly bench is Maximizer concrete found at Home Depot. QuickCrete 5000 is also a very good mix. Both mixes include small fibers to prevent microcracks. They are strong mixes (up to 5000psi compression) with a large proportion of portland
relative to sand and gravel. When I mix concrete myself I like to use the ratio 1 part portland : 2 part sand : 1.5 part gravel. If integral dyes are used make sure it constitutes less than 10% of the mix by weight. More than 10 percent will adversely affect the integrity of the mix. The butterfly bench did notuse integral color because the surface will be acid stained.

The concrete mix should be mixed with water very thoroughly. It is important not to use too much or too little water. Use only enoughto completely mix the ingredients. The consistency should be similar to thick oatmeal. If done correctly very little water should rise after the concrete is poured.
While pouring the concrete make sure to push the concrete into the corners of the form and to get the concrete in between the cracks of the mosaic. It is helpful to lightly
slap the concrete with your hand as you scoop the concrete into the form. This causes the concrete to gel together and to minimize air pockets. Halfway filled lay in the metal reinforcement. Continue pouring and slapping until the concrete fills the form.
If your desire is to have no small pits in the finish caused by air bubbles then the form should be vibrated extensively. Use a concrete vibrator or lightly rap the form with a hammer.

It is best to let the concrete cure slowly. A range air temperature of 65-85 is preferable. After the concrete has hardened enough not to be easily smudged cover with a plastic tarp. This causes the water to evaporate slowly and the piece to cure slowly. Let sit for at least two or three days. It takes 7 days for concrete to reach 75% strength.

After 3 days the concrete should be cured enough to work on the finish but as long as a week might be necessary. Depending on the desired look, finish, and texture one can sand and polish now. If sanding start with a low grit number such as 60 and progressively move to 80,120,220, and even 400 for an extremely smooth finish. I use a regular orbital sander. If you do not want to see any sand or gravel aggregate then sand little or not at all. The portland is the smallest particle in the mix and will be on the surface if vibrated well and left unsanded.

Lastly apply acid-stain if desired. Acid stain can be purchased at a concrete or masonry supply store. Dilute the acid stain with water in a 1:1 ratio. I use a regular plastic spray bottle to apply the stain. A fine mist is best. Spray enough to cover the surface entirely but apply slowly enough to prevent running. Two coats will do.
I used several colors sprayed independently to achieve the mottled look on the butterfly bench below.

Finally, a sealer should be applied to the concrete. Many types of sealer are available from water-based to acrylic to urethane. Satin, semi-gloss, and glossy finishes are also choices to consider.
I used an semi-gloss penetrating sealer on the butterfly bench.