Ztrains: Z Scale Basics: Rock Molds 101

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Learn To Make Your Own Rock Molds

One of the model railroad tasks I really enjoy is creating new rock molds for my Z scale scenes. I find creating my own molds really adds a custom touch to my scenes. If you can hold a 1" brush, you can make your own molds too.

I've found when people hear the word "rubber molds", they often tend to think about the slightly more complex 2-part RTV (room temperature vulcanizing) rubber. Even 2-part rubber can be a relatively simple process but today we're going to be working with the even easier to use latex rubber.

The latex rubber we'll be using is made by Woodland Scenics. It has the consistency of a slightly thinned pudding and brushes on to your model master (the piece you wish to copy) very easily. Latex rubber cleans up easily with soap and water but when cured is very durable. Latex rubber also capture the detail of your model masters very well, making it ideal for rock casting.

This kind of mold making is a lot of fun and will get you started on your way to creating your own unique rock work for your layout. In short, you simply need to brush the latex on the master and wait for it to cure. To insure your success with your molds, we've created an illustrated guide for your reference with a few tips and tricks. As always, have fun! Ok... let's get started making our rock molds.

Make It Clean And Let It Dry...
There are two simple but important things to remember when making your latex rubber rock molds. First, make sure your mold master is clean and dry. If you're using a rock as the master, you can rinse the rock off an let it dry for a day. If you're using wood as your master, brush off all loose bits of wood and brush on a coat or two of fast drying polyurethane. This will seal your wood to a degree and make the removal of the finished mold much easier.

The second thing to remember is to allow each thin coat of latex rubber to thoroughly dry before applying the next coat. At a minimum I'd suggest three coats of latex rubber with 24 hours between coats You can add more than three coats for an even more durable mold.

1. Start Clean.
Make sure your mold is clean and free of dirt and debris. You can wash your rocks with soap and water and let dry for at least a full day prior to applying your latex rubber.

2. Patience.
It's vital to allow each coat of latex rubber to fully dry before brushing on the next coat. Again I'd suggest 24 hours between coats. Patience is a virtue when making molds.

3. Make Several At Once.
Many times it's hard to visualize how a portion of a real rock or a piece of wood will look when molded, cast and placed next to your Z scale trains. I'd suggest making several molds at a time, this way you increase the chances of getting that perfect mold!

4. Don't Stop At Rocks.
Rocks are likely going to be your main model for making rock molds but don't stop there... experiment, try other masters and surfaces. In this article I used a piece of wood I found in my yard. It had a layered rock look to it that I thought would be interesting. In this photo I cast it in gray hydrocal. Maybe you could color it to work in a desert environment?

5. What The Heck Is Cheesecloth?
In this article I used cheesecloth as a way to create a stronger mold. You can usually find cheesecloth in your local supermarket. It's used for several things including wrapping, can you guess... cheese. Also used for straining liquids in soups as well as a host of other kitchen-related tasks. You can also use gauze pads for mold reinforcement.