|Step 1 : Materials|
I used the blue Styrofoam (DOW) that I picked up at my local Lowes. Here in South Carolina all I could find was 3/4″ sheet. Later on I found thicker pink foam (Owens Corning) at a Home Depot. I like the blue foam as it tends to ‘fracture’ in a rock-like way. I haven’t tried the pink stuff but it appears to be similar. There is a green foam you can get but it has more of a fiber-like structure to me .. I used it for stratified rockwork in another project.
Here I have some scrap Styrofoam and plywood which I will use to demonstrate my method. Note that I will deliberately glue the different layers of foam to create a stepped set of layers/strata .. making use of the 3/4″ thickness of the foam. You can hide the joints with spackle .. but much rock is layered so why not make use of it?
|Step 2 : Stack and Glue|
Glue the Styrofoam sheets together. If you live in colder climes you can find thicker sheets then the 3/4″ I used. Like I said, I didn’t have the pink Styrofoam others use available locally, so I can only talk about the blue stuff. I used ‘Liquid Nails Foam & Panel Adhesive”. Make sure you use an adhesive that specifically works with foam as many will melt it.
Read the label as some foam specific adhesives will only work foam to wood .. and not foam to foam. Go figure.
|Step 3 : Implements of Destruction|
These ‘steps’ .. are in no order what-so-ever and the tools are up to you from knives to your fingers. Whatever works.
I used a pocket knife to gouge the foam. Stick the blade in and pry up. Foam will fracture and pop out leaving random texture. I like the pocket knife as the blade is nice and sturdy and this process isn’t exactly delicate work.
|Notice how the foam is fracturing. When you stick the knife blade in and pry up .. it ‘pops’ or fractures .. making a very nice ‘rocky’ texture.|
|Use your thumb and fingers. Pry, claw, scratch, twist, poke, prod .. whatever.|
|The foam cuts easily. Use the knife to cut .. but continue to create texture even while cutting .. slice in and twist the blade. You want it to fracture and not so much cut cleanly.|
|I had a sheet-rock saw handy. Fine. Sliced off a corner. Yea .. nice rough texture there!|
|Took the saw and dragged it down and across the surface to rip and tear.|
|How about another ledge? Easy .. just slice away.|