Artificial Rock Painting Technique
This artificial rock painting example is shown on a fireplace that is originally white in color to better emphasize the process involved with this technique
How to always produce consistent artificial rock coloring results
There are many different methods you can use to give your rock near perfect and realistic color. Popular methods include acids that burn the outer layers of the concrete, various painting methods and add-mixes and pigments in the mix. There are benefits and disadvantages of each method but ultimately the pigments vary from one mix to the next easily and acids are difficult and dangerous to use without proper equipment and instruction.
The easiest, most cost effective (and fool proof) way to color artificial rock is to use watered down paint (water based paint only) and spray the color layers on with a pressurized spray system. Typically you will need to mix the paints at the ratio of one part paint to three parts water in order to have create a mist when sprayed as opposed to clumping and blotching together.
The paint will be applied in many layers and there is fantastic flexibility in that you can paint as many layers as you want and the end result will only look better and better. Should you paint something that you are not satisfied with you can simply apply a heavier misting of a single base color over the rock. Once dried this will basically leave you with a fresh palate to begin painting again.
Painting a heavy base coat is also a good method to change the fundamental color of your concrete which is probably a shade of grey to begin with. If you wanted to have a rock that was brown or red in base color this is how you could accomplish this. The artificial rock painting technique that you are learning here will result in a granite or speckled look as this is one of the easiest to accomplish.
If you were to give a close inspection of a real rock you would see that it is not simply grey, brown or red. The rock is likely made up of a rainbow of colors in varying amounts. It is very common to find yellow, red, blue, black, white, tan and brown speckles in what appears to be a predominantly grey rock. You will want to mimic this layered, freckled look with your painting technique.
The tools you will need to paint your artificial rock
Professional quality spray equipment can cost a lot of money and hand held pump action spray bottles produce low quality results. So a good middle ground for the only tool you need for this process is a hand held pump up spray bottle. These are a good buy because they can produce great results, with practice, and they are affordable enough for everyone to own a set. If you need to pinch pennies you can get away with a minimum of 2 or 3 sprayers or else you will spend almost all of your time changing the paint and cleaning the sprayers out. Ideally you want to have a dozen or more sprayers that contain dedicated colors.
You will attempt to mix 3 parts water to 1 part paint to get a result viscous enough to flow through the sprayer in a mist. This takes practice to achieve perfect misting and you must meticulously maintain your equipment or you will lose the fine misting ability. You will find that for many paint colors you will need to dilute greater than this to be able to achieve a fine mist spray as opposed to blotchy paint splatter and jammed up sprayer nozzles. You can increase the water content as much as necessary keeping in mind that the more water you use, the greater the number of coats your paint job will take to arrive at desirable results.
The layering process involves spraying very light misting coats of alternating paint colors onto your rock. You will also vary the concentration of these colors to create color variations on parts of the rock that resemble mineral content, weather staining etc.
Outline of the artificial rock painting process
You will want to choose an overall base color - grey, brown or red are the most common three. In this example we are using brown as our base color so we need one light brown and one dark brown as the minimum to achieve a realistic finished effect.
1) Light brown (tan)
2) Dark brown
You will then need some highlighting colors. In this example the fireplace is being painted to color match the floor and these are the colors used to highlight:
4) Light grey
And finally you will always require these two colors for almost all fake stone painting:
To arrive at the correct finished product you will apply the paints in multiple light misting layers. In most cases you will wait between coats for the previous paint to dry so they do not bleed together but you can also experiment with adding two wet coats of different colors to achieve interesting and unique blending and shading results. In total this example took near to 50 individual coats of paint to arrive at the finished conclusion which is not practical to show in individual steps. Use the pictures as a general guide and then experiment on your own - it really is hard to mess up this process since you can continue to paint layers overtop of one another.
NOTE: White should be used very sparingly (if at all in some cases) and only as the very second to last coat. Black is also used sparingly though more liberally than the white. You can use black throughout the process with the other colors but your very last coat of paint should be as fine a mist of black as you can manage to spray.
Using goggles and gloves is strongly recommended. This painting process involves a great deal of overspray so good tarps and drop cloths are also a good idea. You may find that the sprayers have the tendency to mist occasionally, and sometimes "choke" and spit undesirable globs of color. In this situation you can use a sea sponge to dab and soften the globs of color. A bucket is a must have for spraying your paints into while fine tuning your sprayer. The fine tuning to keep a good misting effect is pretty much a constant throughout the process and you will waste more paint in the bucket than on your artificial rock. This is the price to pay to have a perfectly misted artificial rock as opposed to blotches of splatter and color.
Always turn your sprayer upside down and spray until the nozzle and tube are blown clean. If you let paint dry in the tube or nozzle, even for a few minutes, you may find yourself doing major surgery to your sprayer to clean it out. Another highly recommended idea is to twist the lid to release pressure in the sprayer when not in use. If you leave it pressurized and accidentally knock it over or depress the trigger you might get paint everywhere - or even a blast to the face which will serve as a strong reminder to release the pressure next time if not something even more serious.
In picture one you can see how you should begin with light misting layers and try to observe direction of the spray in your approach to mimic the flow of colors in naturally occurring stone. Picture two shows how you will interject spots of contrasting color which will be covered over by your base colors in the following 30-40 misting layers.
Picture three is difficult to see against the white background but consists of a medium - heavy misting of yellow. Picture four displays how the base colors will be added overtop of the highlighting colors. This process is repeated over and over again, varying the concentration of colors, order they are applied and the drying times between layers.
This is a time intensive process but as you can see the results are remarkable. Because the painting subject used was completely flat and smooth the finished result almost looks like polished granite or marble. This effectively turned the focal point of the room from a plain white drywall fireplace to a fireplace seemingly hewn from a massive block of granite. The finished results are even more impressive in person than in the pictures.
Sealing and weather protection for outdoor artificial rocks
If you are using this technique to paint an artificial rock that will be placed outdoors you will also need to weather protect the paint job. You will need to use a water based concrete sealing product that you will also apply in layers via a spray bottle. Apply in multiple coats and let dry in between and you will find the paint will be protected for a minimum of a few years outdoors. Re-application is easy when required. Simply make sure the rock is clean and dry and spray a few more coats of water based concrete sealer on one at a time allowing drying time in between.
Some people prefer to seal the rock only the initial time and let the weather add to the natural effect of the stone. Since you have so many layers of paint you can readily do this without problem. Leaving the rock to weather outside can also result in moss growing on it - just like naturally occurring stone.
You've built the first of many wonderful rock additions to any yard or building. If you'd like to view the advanced artificial rock tutorials proceed to the next page.