How would you go about producing an antique finish on concrete?
This all depends on what is meant by an antique finish. A simple means of giving the effect of age is to add manganese black or carbon black (not more than 10 percent by weight) to the cement. If care is taken not to mix the pigment in very thoroughly, the surface will show irregular darker hues. The effect can be emphasized by rubbing down the surface with a piece of coarse sacking immediately after the form is stripped. This will simulate a finish produced by long exposure to weather. Certain colors could also be used to create an antique effect. Shades of buff or brown can be obtained by staining with ferrous sulfate solution and shades of green with copper sulfate solution. The depth of color achievable depends on the strength of the solution used, the period of exposure and the age of the concrete. It is best to apply a sulfate solution to concrete at the earliest possible age. A couple of handfuls of ferrous or copper sulfate to a gallon of water would be normal for an initial treatment. The solution should be well soaked over the surface for about 15 minutes before being rinsed off. The treatment should be repeated until a suitable color effect is obtained.