Creating Realistic Corrugated Roofing Part 1

Written by Shawn Branstetter, photos by the author.

Bill of Materials

Ferric Chloride (Mine is from Radio Shack called Archer Etchant. This can also be found at some art supply or hardware stores.)Water with liquid dishsoap
TweezersPaper towels
Razor blade or hobby knifeMakeup sponges
Ak-Interactive acrylic rust colorsAk-Interactive acrylic rust pigments
Mineral SpiritsFlat Varnish

Aging metal roofs and siding have always been a sore spot with me. I have tried, over the years to achieve the patina look with paint and never could quite get the color right, or at least to my liking. This technique has been around for some time and I can remember reading Mic Greenberg's article in the Narrow Gauge Shortline Gazette way back in the 1980's, however, never gave it much thought. Fast forward to now when I stumbled upon this technique again from Marc Reusser.

The idea is rather simple, using ferric chloride of some type, submerge the aluminum roofing material, clean up and weather it.

What is ferric chloride? Iron(III) chloride is also know as ferric chloride, which is commonly used by computer guys (and gals) for etching PC boards. Modelers are, and have, been using it to patina copper, aluminum and other metals with fantastic results.

Using this material can be hazardous so precautions must be observed when working with it. I always use rubber gloves along with eye and respiratory protection.

Setting Up a Workstation

I like to set up a work station to simplify the process and to keep my table organized. To begin, I have a small glass container to hold my etchant, followed by a container of water with dish soap added. Paper towels will be used to lay all the material on.

Getting Started

There are a couple of items to note before we actually begin; first, this only works on metal. Card stock, styrene and other material will not work. Second, if you are going to be using aluminum foil to create your own roofing material, typically, the store bought brand is extremely thin and the etchant will completely dissolve it in seconds. Be sure you are using thicker or heavy-duty foil.

The material I am using is from Builders in Scale which comes in many scales and styles. It's thick enough to handle the etchant however, thin enough to look very realistic. Out of the package it is very shiny as seen above. Cut your pieces to width and lay them in a pile on your work station. You will want to work with them one at a time.

On some of my sheets I like to add holes and dents to add more character. The etchant can and will attack these holes further adding to the aging process.

Using tweezers, hold each sheet in the etchant for a few moments. You will notice nothing happens at first. Be patient and again, work one at a time. Bubbles will appear and then a violent reaction will take place as the etchant is eating into the material. Remove the sheet and quickly place it into your water solution to neutralize the etching process.

Now, place them on a paper towel to sit. The pieces will look dark grey/black and tarnished which is exactly what we are looking for.

While each piece is still wet, use a toothbrush to remove the top coat of etched material. It will start to take on a lighter grey appearance as you are brushing them. Continue the process by dipping the material into the water and then brushing them, repeating this process a couple of times to stop the etching process and clean the material throughly. Allow them to dry on the paper towels. Do this with all your sheets and allow them to dry overnight.

Acrylic Weathering

Now, in part one, we will discuss weathering your metal sheets with acrylics and pigments. In another article we will use another natural technique using water. But I digress.

We will begin by using a make-up sponge as our paintbrush. Depending on my weathering, I may use a more porous sponge such as the ones used for painting home interiors. Tear a small piece off of the sponge and use tweezers to hold it while you work.

Add color beginning with the darkest first. I like to lightly touch the sponge into the paint and dab the access onto a paper towel until almost dry.

Build your colors in layers using multiple pieces of sponge in order to keep the weathering patterns different.

Once I'm satisfied with my background colors, I will use pigments to add more texture and dimension to the weathering effect. Starting with darker colors first as before, place a small amount of the pigment onto the desired area with a brush or sponge. Dip another brush into your mineral spirits and lightly dab it onto the pigments, allowing it to flow into the material. Make sure the spirits are running with the flow of rain water.

You can further the weathering effect by dusting on a thin layer of dirt. This will also tone down your colors if desired. After everything is dry, spray the metal sheets with a flat varnish to protect your color and lock everything into place.

In part two, we will look at adding peeling paint to our tin sheets. 

About the Author

Shawn Branstetter's picture

Shawn Branstetter

I am a graphic designer and front-end developer, creator of Shortline Modelers. I have been a life-long model railroader with a focus on California shortline and logging railroads.


eTraxx's picture

Excellent article. I was doing something similar a while back and mostly by accident discovered that scrubbing a bit of white weathering powder on the tin helps moderate the colors ..well .. I think so at least! :)

"I drank .. WHAT?"
--- Socrates

Shawn Branstetter's picture

That looks awesome!

Shawn Branstetter