Monday, May 4, 2015

Rock On!

Real is pretty much always better than fake, but when it comes to rocks, there's just something about an artificial rock that I find fascinating.  Armed with some mortar mix and a few how-to videos off YouTube, I set out to create a few of my own.

Here is the before shot:


Step 1: I planned to create five rocks total, and wanted a nice balance of tall and short.  So I bent 3/8" thick rebar with my foot into the shape I wanted and wrapped some 1/4" hardware cloth around the rebar skeleton.  I secured the hardware cloth to the rebar with wire in as many places as I could to help rigidify the hardware cloth.


Step 2: There are a few keys to getting a fake rock to look like the real thing.  The first is the shape.  Rocks are usually very angular.  Maybe it broke off from a bigger piece of rock and has slowly eroded over time to round off its corners.  Whatever its story might be, it has to look like it has been sitting around for at least a few thousand years.


Step 3: I experimented with different mortar mixes.  This mixture in the photo below is a 3:2 mix of Portland cement to Lane Mountain sand.  It hardened into a very dense material that was completely smooth and rock-like.


Step 4: I wanted the rocks to be orange, brown, and grey in order to match the brick pathway surrounding them.  I knew it was important to vary the color of each rock while maintaining a cohesive palate.  In each batch of mortar mix I made, I put in different amounts of color so that no two batches would be exactly the same.  This is still the first coat (aka "scratch coat") but some of it is going to show through.


Step 5: Most of the rocks I made are hollow, but I found a great way to hide the scraps of paver stones left over from making the pathway.  No one will ever know!


Step 6: After allowing the scratch coat to dry, I applied the second and final coat.  Then I took some crumpled up aluminum foil and pressed it against the surface of the rock to texturize it.  I let it dry for a few hours until the cement had the consistency of packed sand, and then took a paintbrush and brushed over the entire rock.  At this point the cement is at the perfect stage for making cracks, dents, and crevices and then eroding it away with the paintbrush.  Basically it's just a matter of messing with it until it looks like a real rock.

Here is the final picture before I started getting carried away adding plants:


And now these heat-loving plants have a new little slice of paradise to call home.


So now you want to create your own rock, right?  Let me know how it goes!  The total cost was around $200, or about $40 per rock.  Definitely cheaper than buying a real rock - which would also include renting a backhoe to move it into position.  The time it took was around 15 hours total or 3 hours per rock.  I am sure if I were to do this again I could do it in 10 hours now that I know what I am doing.

Here are the materials I used:

Tools:
- Wheelbarrow for mixing
- Rubber gloves (wet cement is caustic)
- Shovel for mixing
- Small bucket to hold mortar mix when applying it
- Triangular trowel to apply the mortar mix to the hardware fabric
- Aluminum foil
- Paint brushes with different sizes and thicknesses

Ingredients:
- 4'x3/8" rebar poles
- 1/4" hardware fabric
- Mortar mix
- Water
- Cement color

10 comments:

  1. Great work there! It looks good and very realistic!

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    1. Thanks. Yea hopefully they're not so realistic that people won't believe me when I tell them they're fake.

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  2. Oh my gawd, you made your own rocks! That's just crazy-cool.

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    1. They go really well with agaves too. :)

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  3. You never cease to amaze with all of your talents! Your rocks look real! I could do the rebar/hardware fabric/ concrete part but the part about roughing them up and making them look natural would be a challenge!

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    1. It's definitely an art but it's easier than it looks.

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    2. That was inspiring.. I have used concrete in the past to make fountains. The stuff is very heavy even when one employs tricks to make it lighter. It would be interesting to make a lighter artificial rock.

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  4. How sturdy are the rocks? If somebody sat or stood on one, would it crack? It's difficult to tell how thick the mortar ended up being. Look great!

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