Foam Background Guide

No terrarium or vivarium would be complete without a custom background, right?

File:Foam background (36x18x24).png

Well, not necessarily - but a custom background can enhance the naturalistic feel of an enclosure and provide more usable space for plants and animals.

Hobbyists use many different methods to build custom backgrounds, and the Foam Method is among the most popular.

Pros and Cons

Pros:

• Longevity: Foam backgrounds can last up to 10 years, often longer
• Durable: With proper precautions, this method can even be suitable for large reptiles
• Highly customizable: Can be used to create ledges and other features, attach hardscape, and apply substrate texture to walls

Cons:

• Extremely messy: Foam is very sticky, and pieces of foam will fly EVERYWHERE if a wire brush is used for trimming
• Time-consuming: This method requires time between steps to cure; don't try to build a foam background in a single day or weekend

Materials

Required:

• Enclosure: Suitable size and type enclosure for future plant or animal inhabitants.
  • Examples: Exo Terra, Zoo Med, Fish tank.

• Safety equipment:
  • Well-ventilated space: Some materials used in this guide release fumes prior to curing that are toxic or flammable. The work space should have plenty of fresh air and ventilation while working and curing.
  • Disposable gloves: Some materials used in this guide will stick permanently to most surfaces, including skin. Gloves can also be used to spread silicone and substrate.
  • Eye protection: Use safety glasses, ideally goggles. You do not want expanding foam in your eyes, enough said.
  • Face mask or respirator: Some steps in the background construction process will send dust or small plastic foam particles airborne. These particles can be dangerous if inhaled - so be sure to use a face mask or respirator when applying or shaving expanding foam, or applying substrate to your background.
• Expanding foam: Polyurethane expanding foam, typically sold in an aerosol can.
  • Examples: Great Stuff ™ Gaps & Cracks, Great Stuff ™ Pond & Stone.

• Silicone: The important thing here is to use 100% silicone, which is free from filler ingredients that may interact with water or living things in your enclosure.
  • Example: ASI Aquarium Sealant, other aquarium-grade silicone, GE Silicone 1*.

• Substrate: Any fine substrate with the desired texture will do, but it must be completely dry during the application process. Substrates or mixtures with some organic plant matter may be more suitable for vines / epiphytic growth.
  • Example: Reptisoil, fine coconut coir, etc.

• Caulk gun: For applying silicone that typically comes in 10-oz tubes.
• Utility knife or Drill with Wire Brush bit: For shaving off the shiny outermost layer of the expanding foam.

Recommended:

• Cork bark: Can be adhered directly to expanding foam to create texture or ledges.
• Other branches / hardscape: Wood and other hardscape can add habitable space for plants and animals, and aesthetically adds depth.
• Vacuum cleaner: To clean up tiny bits of foam, and substrate.

* There is some debate within the community over the safety/purity of GE Silicone 1. Aquarium-grade silicone is strongly recommended.

Pro Tip: We strongly recommend buying all supplies before you begin, and buying more than you think you'll need (unless you live across the street from a hardware store). It's not fun to spend half your project time driving back and forth from the store to get more supplies! You can usually return what you don't use later.

Directions

Step 1: Prepare the enclosure

Use a damp cloth or paper towel to gently clean and prepare the enclosure. Dust or debris may make it difficult for silicone or foam to adhere properly. Allow the enclosure to dry completely before continuing.

Step 2 (optional): Apply a thin silicone foundation

Some experienced hobbyists have reported issues with foam backgrounds partially peeling off or become unstuck after construction.

It's not known why these issues occur (e.g., environmental factors like temperature or humidity, user error, etc.), but using the caulk gun to apply either a thin layer or a few long beads of silicone across the surface area you intend to cover with expanding foam can provide a stronger foundation for the foam to adhere to.

Let silicone cure 24-48 hours, until the acetic acid (vinegar-like) smell is completely gone.

Step 3: Apply expanding foam

Now's the time to put on your eye protection, face covering, and gloves. Increase ventilation in your workspace by opening windows and doors (as weather permits).

Lay the enclosure gently on its back on a soft, flat surface like a rug, carpet, or towel-covered floor.

Shake the can of unopened expanding foam vigorously per the instructions on the can, and screw on the application tube.

Then, apply the expanding foam by holding the tip of the application tool about an inch (2.5 cm) from the enclosure, and using slow, smooth motions to apply foam evenly across a single side of the enclosure. Take breaks as needed.

Allow this side to expand and dry for at least an hour, then repeat on the other sides of the enclosure you want to cover, turning the enclosure as needed so that the side you're applying foam to is face up.

Tip:

• Leave at least 2 inches (5 cm) of clearance from the edge of the foam to the top of the enclosure, as well as the doors of front-opening enclosures . Remember the foam is going to expand while curing - if you're not careful, it can expand far enough to break the doors of the enclosure or seal them shut.

Step 4: Touch up foam and add hardscape

Repeat Step 3 until each wall is covered. Use expanding foam to attach cork bark, wood, and other hardscape to the background by pressing pieces into freshly-applied foam.

Allow 24-48 hours for all of the foam to cure before continuing.

Step 5: Shave off the surface of the foam

Once the expanding foam is done curing, and you're done attaching your hardscape, it's time to remove the shiny surface layer of the foam to add texture and improve the adhesiveness to silicone.

After putting on your protective eyewear, face covering, and gloves, use either a utility knife or drill with a wire brush drill bit to remove the shiny surface layer from all of the expanding foam.

This is also a good time to carve texture into the foam, if there's a "look" you're going for.

Step 6: Applying silicone and substrate

You'll need your safety equipment for this step, and it has to happen pretty fast.

Lay the tank on its side, with the side you're applying substrate to facing up.

With your gloves on, use the caulk gun to apply lines of silicone across the surface area of the expanding foam. The silicone will begin curing immediately, and will lose adhesiveness as time goes on, so you want to do this quickly.

Once you're done applying the silicone lines, use your (GLOVED) hands to spread the silicone evenly across the background, no more than 1/4" thick. Try to cover all of the foam.

Then, pour your substrate mixture onto the uncured silicone and gently but firmly press it down with your gloved hands - use more substrate than you think you need. Try to cover all of the foam.

Allow 24-48 hours for the silicone to cure, until it no longer smells like silicone.

Repeat this step until the first layer of substrate has been applied to all background surfaces.

Step 7: Touch up

Stand the enclosure up and allow loose substrate to collect in the bottom of the enclosure. Vacuum up as much as you can.

Unless you've done this a hundred times, or you're some type of silicone-substrate artisan, you'll likely notice spots where you need to go back and touch things up with more silicone and substrate.

Remember to use your safety equipment, and a fresh set of gloves each application.

Repeat until all of the foam is covered, or you're satisfied with the result!