Studio-Quality FDM Terrain: Part 2 – Painting & Weathering

Prefer to watch? Our full video tutorial demonstrates every stage of the process, with plenty of additional context and advice along the way. 

We'd recommend checking it out!

Printing & Preparation

• FDM printer and PLA filament (black recommended)

• Heat gun

• Coarse or medium builders' sand

• PVA glue

• Sandpaper or abrasive pad

• Old brushes, including a large brush for basecoating

Texturing & Painting

Additional Tools

• Household sponges, cut into manageable pieces

• Mixing containers

• Paper towels

• Small detail brushes

• Super glue

• Clippers

• Water for thinning and cleaning

A note on materials: These are the products we used in the UK, and some have been chosen by virtue of dwelling in my shed already. Don’t be afraid to substitute with similar products from your own collection or local hardware or hobby shop. 

If you’re not sure, test unfamiliar materials on a spare print before applying them across an entire collection.

Rather than drybrushing the stonework, we're using household sponges to build up the colour.

This is an important distinction: drybrushing can catch and emphasise FDM layer lines, while sponging introduces irregular patches of colour across the surface.

First Colour: Dark Anthracite

We used a dark blue-grey masonry paint from a tester pot.

Method

1. Cut a household sponge into small, manageable wedges.

2. Load the sponge with paint.

3. Dab away the excess on a paper towel.

4. Apply the paint in irregular patches across the masonry.

Aim for approximately 75% coverage, leaving some of the original black visible in recesses and between stones.

Avoid uniform patterns. Rotate the sponge and vary the pressure to create a natural-looking colour distribution.

Second Colour: Light Sandstone

Next, repeat the process using a light, neutral ivory or sandstone colour.

We used a colour called Sandstone, as it’s more neutral, but you can use ‘Magnolia’ which is more commonly available.

Apply this more sparingly, covering approximately 30% of the surface.

The result may look rather stark at first, but the subsequent washes will bring the colours together.

For the wooden elements, we used Dulux Dipped Chocolate, a neutral brown household emulsion.

Paint the wooden floors, beams, scaffolding and other timber details, taking care not to cover the surrounding stonework.

Once dry, lightly drybrush the wood using the same Sandstone colour from the previous step.

This brings out the grain and sculpted details.

Don't worry if the highlights look too bright. The washes will substantially darken and age the wood.

While we’ve got this sandstone drybrush ready, give all your previously sponged stonework a look over - lightly pick out any details that the sponge failed to reach.

Dreadwatch includes separate iron-barred windows and doors, which can be printed in either FDM or resin.

For this batch, we opted for resin to preserve the finer details with less preparation, but both methods work perfectly well.

Method

1. Test-fit the windows and doors, then secure them to the terrain using super glue.

2. For broken windows, use clippers to cut selected bars at irregular points, creating a more naturally damaged appearance.

3. Basecoat all exposed ironwork using a dark metallic paint. We used Citadel Leadbelcher on the windows, doors, spikes and other metal details.

We also picked out some of the visible Keystone connection holes with metallic paint, allowing them to collect a little rust colour during the later weathering stages.

Don't worry about achieving a particularly refined metallic finish. The subsequent washes and rust effects will do most of the work.

The first wash introduces depth and begins bringing the stonework colours together.

We used Vallejo Wash Effects for Dark Vehicles, a dark acrylic wash suitable for larger terrain surfaces.

Method

1. Apply the wash generously across the stonework and exposed metal.

2. Work it into cracks, recesses and overlapping details.

3. While the wash remains wet, gently dab raised surfaces with a clean paper towel to recover some of the lighter highlights.

4. Allow everything to dry.

Avoid applying this initial wash heavily across the woodwork. We'll treat the wood with the dirty brown wash in the next step.

The black wash should significantly reduce the stark contrast between the grey and ivory sponge layers.

Next, introduce some earthy colour variation using a homemade dirty wash.

Our mixture is:

• 200ml empty bottle (I’m using a finished bottle of vallejo airbrush thinner)

• 80 drops Burnt Umber Ink

• 30 drops Black Ink 

• 10 drops Crimson Ink

• 45 drops Sap Green Ink

• 20 drops Raw Sienna

• 50:50 Mix of:

  • Matte Medium

  • 10:1 Mix of Distilled Water & Flow Aid

We’ve used Liquitex branded stuff here, but any artist-grade brand will do. You can adjust the consistency to suit your materials and preferred application.

Applying the Wash

Using a large brush, apply the mixture in broad, irregular patches across approximately 40–50% of the stonework.

Rather than treating individual bricks, work across whole sections of masonry, allowing some areas to develop a greenish-brown stain while others retain their cooler grey appearance.

Let the wash settle and dry naturally. Avoid repeatedly dabbing it away with a paper towel, as this can remove too much of the colour.

The objective is to create noticeable variation between cooler stone and warmer, dirtier areas.

Weathering the Wood

Apply the dirty brown wash much more generously across the wooden elements.

This darkens the earlier highlights and creates a more aged, rotten appearance.

Alternatives: Similar effects can be achieved using commercial brown and green hobby washes, such as Citadel Agrax Earthshade and Athonian Camoshade, although these can become expensive when painting large quantities of terrain.

Oil washes are another option for painters comfortable working with that medium.

One of the most distinctive elements of our finished terrain is the rusty ironwork and the orange staining running down the surrounding stone.

For this, we're using Dirty Down Rust, a specialist weathering product that creates convincing corrosion effects.

Preparing the Product

Dirty Down Rust requires thorough mixing.

Pigment can settle into a thick deposit at the bottom of the bottle, so shake vigorously and stir if necessary until the material is properly combined. This can take several minutes.

Use an old brush that you don't mind sacrificing, Dirty Down is a brush ruiner.

Painting the Rust

Apply Dirty Down directly to the metalwork, concentrating on areas where moisture would naturally accumulate:

• Rivets and joints.

• Overlapping metal plates.

• Recessed details.

• Areas where metal meets masonry.

Vary the amount of rust according to the size and exposure of the metalwork.

Large iron-barred windows can support heavier corrosion and more substantial staining than smaller spikes or fittings.

Creating Rust Streaks

The key to convincing rust streaks is to imagine how rainwater would carry rust down the structure, following the contours of the masonry as it goes.

For example, water running off an iron-barred window might drip down the wall, follow a mortar joint sideways, then collect in a recess before continuing downwards.

Following that logic gives us much more natural-looking stains than simply painting straight orange streaks down the walls.

Here you can see the rust streaks in action, alongside a bunch of bird crap!

Building Colour Variation

Thin applications of Dirty Down can dry to a relatively bright orange. Additional layers can create progressively darker, richer rust tones.

Once the first application has dried, revisit selected areas to build deeper corrosion and introduce variation.

Reactivating with Water

Dirty Down reacts to water, allowing you to adjust the dried effect. Using a clean brush lightly dampened with water, gently work over selected raised metal edges.

This can thin or redistribute the rust effect, revealing more of the original gunmetal and creating additional tonal variation.

Important: Test water reactivation on a small area first. The result depends on the amount of water, product thickness and surface beneath.

For a more detailed exploration of Dirty Down's properties, we recommend Vince Venturella's dedicated tutorial.

This Azerai Sigil is a good example of the effect of layering dirty down, and water reactivation to create an interesting finish.

Our final painting step is another application of the Vallejo black wash. Unlike the earlier all-over wash, this application is highly selective.

The objective is to reinforce the deepest shadows and restore definition after the rust weathering.

Concentrate on:

• Deep recesses beneath archways.

• Overlapping bricks and masonry.

• Areas where rusty metal meets stone.

• Joints and overlapping sections of ironwork.

• Any details that need stronger contrast.

Use a smaller brush and avoid covering entire surfaces.

In particular, don't obscure all the rust effects we've just created. A little black wash in the deepest recesses helps break up the orange and gives the metalwork additional depth.

Step back occasionally and assess the piece as a whole. Only add more wash where it genuinely improves the definition.

Once dry, the painting is complete.

And there we have it! Our Dreadwatch terrain is finished, and we're delighted with how it's turned out.

Across these two guides, we've taken raw FDM prints through surface preparation, texturing, painting and weathering, building up a finish that's suitably crusty, grimdark and lived-in.

The combination of textured masonry paint, modelling paste, sponge painting and layered weathering has helped disguise those telltale printing artifacts, while introducing plenty of natural variation across the stonework, wood and metal.

We've also deliberately mixed inexpensive household materials with specialist hobby products. Hopefully, you've discovered a few new techniques and materials worth trying on your own projects.

Of course, this is simply the approach we've arrived at after a fair bit of experimentation. There are plenty of other ways to tackle FDM terrain, and we'd encourage you to adapt the process to suit your own needs.

Whether you're preparing a few pieces for your gaming table or an entire ruined city for miniature photography, we hope these guides have given you some useful ideas for achieving a more convincing finish.

If you're new to Dreadwatch or our modular Keystone Terrain System, we've got more videos covering printing, assembly and building your own ruined structures.

Dreadwatch / Keystone YouTube Playlist →

We'd also love to see your own painted terrain. Join the Bestiarum Discord and visit our dedicated Keystone channel to share projects, exchange tips and find inspiration from fellow hobbyists.

Bestiarum Discord →

Explore Dreadwatch →

Happy hobbying!