We had a bizarre mystery closet in our apartment that had no door and was right next to another closet. We hid it behind a sheet and started calling it "the bat cave". But for Halloween, I decided it needed something different... Here is how to build your own (temporary and storable) bat cave.
You will need:
--junk fabric, enough to cover your area
Step 1: Building the Cave Walls
To start you will need to dye the fabric you will be using as the cave walls. I was able to find a lot of cheap fabric at Walmart for $1 a yard in the sale section and a pack of black dye. I also used a bottle of the black RIT dye.
Follow the instructions on your dye package. To get this gray color, I only dyed my fabric in the black dye for ten minutes instead of thirty.
Make sure your fabric is rinsed and dried!
Step 2: Stalactite/stalagmite Structures
Start building the bases for your stalactites and stalagmites by building cones out of newspaper. Make sure you have a strong structure underneath--either something for it to sit on or perhaps a frame of chicken wire or something. I built mine out of only newspaper and that turned out not to be strong enough once the foam got it wet, and they sunk in and collapsed.
On my second try I stuffed them with newspaper and empty foam cans, and that worked pretty well but not the greatest. So make sure you have a frame in the cones!
Make them of varying heights and widths, they don't have to be (and shouldn't be) "perfect".
DO NOT use duct tape! The expanding foam needs air to dry as well as a surface to stick to, and since the duct tape is slippery and will also cause it to dry more slowly, the wet foam will simply slide down your structure and build up at the bottom.
Step 3: Creating the Fake Rock
Cover your structures in the expanding foam, following the directions on the cans. Your foam may slide down your structures and will pile up at the bottom, so make sure to lay down newspapers or cardboard or both. Newspapers will make it easier to move your stalactites later, so I would recommend that.
The lumpier look came from working in circles from the base of the cone upward; however this seems to waste a lot of foam and creates a heavier, bumpier looking cone. The taller, smoother look came from working in vertical lines moving back and forth along the cone surface.
As well as stalactites and stalagmites you may want to make some rock formations for the walls or rocks for the cave floor.
In terms of expanding foam, the EcoFoam seemed wetter and would create a flowier, more unified surface as it expanded. GreatStuff seemed less likely to slide down but also did not expand into itself as well, creating a surface that had a "rougher" (that is, lumpier and less flowing) appearance.After the stalactites have dried, remove them from your work surface and trim any newspaper or cardboard that is showing around the edges.
Step 4: Fake Rock (continued)
Using whatever color scheme you have picked for your cave rock, paint your foam with the craft paint. You can be as detailed or plain as you please; I simply mixed white and black paint without much concern as to streaking or shade so that there was some seemingly "natural" variation.
DO NOT use spray paint! Spray paint is known for eating away foam, which could destroy your stalactites. I tried it on the EcoFoam and didn't see much of a problem, but that could be the materials that the EcoFoam is made of. However you could possibly use this technique to create an interesting "rock" surface, so if you do (and it works), please post a picture and I will add it!
Step 5: Prep Your Cave Zone
Hang up your "background" fabric wherever you are planning to build your cave. Then create a pile of surfaces for you to place your stalagmites on. Try varying heights or even protrustions (such as the traffic cone shown) to create an uneven surface. After you are satisfied with your cave surface, drape your dyed fabric over these surfaces to create your cave walls/floor/ceiling. Try to show as little of what is underneath as is possible!
Step 6: Hang Your Stalactites
If you have a low "ceiling" to your cave, you may be able to attach them directly to that surface. However, I had about three to four feet from the ceiling in our closet to where I wanted the stalactites to hang, so rigged them up with duct tape and string. The duct tape held for about a week and a half, so if you want something that will last longer, you should find some kind of more permanent rig.
As for the stalagmites, arrange them as they look best on the "floor" surfaces you put under the fabric.
Step 7: Add Your Finishing Touches
Let your bats move in (i.e. hang them up) and keep an eye out for a secret batmobile door.
Sit back and enjoy your very own new portal to the underworld!