Paint Techniques for Realistic Stone Work
by George Riley/photos by the author
Naturally occurring materials such as wood, brick, stone and even concrete have variations in their color and finish. To represent these variations in model form we will outline a technique that has been used by plastic armor (military) modelers for a number of years and refined for our purposes. Our goal is to easily create subtle variations in color and texture as it applies to model railroad structures.
While we will be recreating finished stone work on this project, the techniques that we use can be applied with color changes and experimentation to scenery, structures and rolling stock. We are using Custom Model Railroads' arch bridge for this project. It is constructed from laser-cut acrylic sheet material that inherently has a smooth finished surface.
Since our bridge is not affected by moisture we used water soluble paints and washes. If you are working with wood or cardstock it is recommended that you use solvent-based finishes so as to not damage the base materials.
Step One: Once the bridge is assembled it is given an overall coat of base color. In this case Krylon gray spray primer has been used. Allow the base coat to dry hard. Set the bridge aside for one week to assure that the paint is fully cured. You will know the finish has cured when you can no longer detect the familiar "paint smell" of evaporating solvents.
Step Two: Track will be applied at a later stage to the bridge deck. By painting the deck any missed areas of ballast will not be apparent when the final ballast is applied. In this step the bridge is masked off from the deck and a spray of "spatter" stone texture decorating paint is applied. We chose a color that would match our brand of ballast. Once the deck is painted allow to dry thoroughly and remove the masking tape. There are several brands of textured "spatter" spray paint on the market that are available from any of the major home improvement stores. Two of the more available brands are Flex Stone and American Accents.
Step Three: Since we are attempting to replicate a light gray limestone finish, we have chosen three lighter colors to highlight individual blocks. Chosen were Polly Scale Earth, BAR Gray and L&N Gray. Randomly paint individual stone blocks with a mixture of the colors. Each stone does not have to be painted. Once you are satisfied with the results allow the paint to dry thoroughly, usually overnight.
Step Four: In this next step we applied a black paint wash. This wash is made by thinning normal strength Polly Scale Steam Power Black paint with a mixture of water and a wetting agent. In this case we used Kodak PhotoFlow; however, a couple drops of dishwashing liquid can also be used. The black paint is mixed with the water as we go. This allows us to vary the amount darkness of the wash. You do not want the coverage to be uniform but rather to be lighter on the reflective surfaces and darker in the crevices and areas that would have depth. Again allow this coat to dry thoroughly before going to the next step.
Step Five: The final finish is accomplished by a technique known as "dry brushing." You will need a paint rag, a soft, stiff bristle brush and a paint that is slightly lighter than your base color. We used a ½" china bristle brush and Testors Model Master Light Ghost Gray paint. For dry brushing, flat oil based paint seems to work better than acrylics since this type of paint has a faster setting time.
The brush is dipped into the full strength paint and then wiped off on the paint rag. A small amount of paint still remains on the bristles. Use a scrubbing motion to apply this remaining paint over the surface of the model. A transparent haze will remain on the model that unifies the under colors and highlights the raised areas. Dry brush all of the stone work, working in the color until you are satisfied with the results.
Step Six: Woodland Scenics Scenic Cement, ordinary white glue or a similar adhesive is painted on to the deck of the bridge and track sections are pressed into the glue while it is still wet. The track was aligned with the retaining edge of the deck to provide a 2" track center.
Step Seven: With the glue on the deck still wet apply an even coat of ballast to the deck and track. Use a dry brush to even out the ballast. Next, spray the ballast with "wet" water (water with several drops of dishwashing liquid). Apply thinned scenic cement over the ballast and set aside to dry. I think you'll agree that the finished product, with all of the depth and texture of the real thing, is worth the time and effort invested.