Faux Rocks That Look Real

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Introduction: Faux Rocks That Look Real

About: I like building things mainly from wood or metal. Especially if they look complicated to make, then I like to think about how to make it. And I love it when the result looks good.

I have been rock climbing and bouldering in the past 20 years and I really like rocks. I already had several small rocks in the back yard and wanted to add some larger ones. Unfortunately, there are no rocks and no boulders in the area where I live.

Real rocks are also expensive and difficult to transport, so I decided I would try to make some rocks out of concrete.

I have seen photos of faux rocks made by other people but they did not look real. My solution to make the concrete look like real rocks, was to build up the surface in multiple layers and to use a coloring powder to get variation in lighter and darker shades. Also I recommend to make more than one faux rock because when there are several faux rocks of different shapes but the same color and structure, they also appear more natural.


Supplies

  • Portland cement
  • Sand
  • Black powder to color cement
  • Chicken wire
  • Styrofoam
  • Tape
  • White paint

All materials that I used were left over from previous projects, so I used what I had. It is possible to use other filler material instead of the styrofoam and it is also possible to use pre-mixed cement instead of the portland cement that I used.

Step 1: Option A: Use Styrofoam and Chicken Wire

I made one really large rock and three medium size rocks. I used the chicken wire only for the largest rock, because I did not have enough chicken wire to wrap all 4 rocks. Both methods worked, but I liked the option with styrofoam better as that gives more strength to the concrete. If you are making faux rocks and never plan to move them, it is easiest to skip the chicken wire.

I used styrofoam to get a rough shape. Styrofoam is light weight, it can withstand moisture and cement sticks well to styrofoam. But you could use for example empty plastic bottles as alternative.

I broke the styrofoam in some large pieces, wrapped a bit of tape around the pieces to keep them stacked together and after that I wrapped the pieces in chicken wire.

Step 2: Option B: Use Styrofoam Without Chicken Wire

Since I ran out of chicken wire, I made the last three rocks by just putting some pieces of styrofoam on top of eachother and then I covered them with cement.


The small rock which is on top of the styrofoam was there just temporarily to prevent that the wind would blow away the styrofoam.

Step 3: Mix the Cement

I mixed the cement in the ratio of 1 part portland cement and 3 parts of sand.

It works best to first put a small layer of water in a bucket and then adding one scoop of portland cement and 3 scoops of sand, then stir the mixture and again add 1 scoop of cement and 3 scoops of sand and stir again. It is real easy to stir the mixture when it is still too wet, so you just keep adding cement and water until you like the consistency. Do not make the mixture too dry as it will not stick very well to the styrofoam when the mixture is too dry.

It is not needed to add the black coloring powder to the mixture at this moment.

I had a second bucket filled with water only, so I had water available to dilute the mixture if that would be needed. Our chicken came to see what was in that bucket.

Step 4: Cement Underneath or Not

I decided to start with a layer of cement under the styrofoam, but that is not necessary. The advantage of starting with a layer of cement is that the cement is all around the styrofoam so the rock can be used in all orientations.

If the rock will be used on it's side, it is best to make the cement at the bottom not flat, so make a dent in the sand before adding the first layer of cement. On the contrary, if you prefer to give the rock a stable bottom to use it upright, it is best to make sure the cement at the bottom is flat.


Step 5: Cover the Styrofoam With the First Layer of Cement

Use gloves to cover the styrofoam with cement. If you make the first layer too thick, it will fall off by it's own weight. So just add a layer of about 2 cm (3/4") thick. The surface of the cement may be quite rough, as a second layer will be added soon.

Step 6: Same As Step 5 But Now on the Other 3 Rocks

I repeated the process of step 5 on the 3 rocks where I did not use the chicken wire. The method is basically the same only here I needed to start covering the styrofoam from the top so the weight of the cement would keep the pile of styrofoam in place.



Step 7: Take a Break

Wait for 30-60 minutes before adding a second layer of cement. In that time the first layer has started to set so the second layer can be added without the cement falling off due to the weight.

The time that I mention is based on me using portland cement. If you use a quick cement mixture, the time might be different.

Step 8: Second Layer

Add a second layer of cement over the first layer. It is a bit like a gentle massage. In principle you want this layer to have a really smooth surface, but you can make some small sharp ridges just like real rocks have.

The second layer is also the moment to add the black powder to get different shades of gray. The variation in color is very important to get the rock to look real. I used a spoon to drop a little bit of powder on the wet second layer of cement and used my hand to rub the powder into the cement. I made sure that I varied where I added the color so that some parts are dark and others are light.

Step 9: Add Small White Details

After the cement had cured for some days, I added a bit of white paint to add some details. I added some white dots and also some lines. It works best to highlight the areas where there are some edges and ridges.

Step 10: Quality Inspection

Our chicken checked the result and I think it was approved.

Step 11: Enjoy

I placed some of the small rocks around my new faux rocks and I like the result.

On these photos you can also see the metal sphere that I made one year ago. I also made an Instructable about that, so check out my previous Instructables if you want to know how I made that sphere.

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Stone Concrete Cement Contest

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    62 Comments

    0
    HughM34
    HughM34

    Question 8 weeks ago on Step 1

    Great 2nd place win. This really looks good. I want to make the inside hollow to hide a metal ammo box to use for a geocache. So would I do the same with Styro foam, chicken wire and tape and cement? It only needs to cover the ammo box but be strong enough incase some kids or people walk on it, but not too heavy. I liked your finishing touches.

    0
    Liebregts
    Liebregts

    Answer 8 weeks ago

    It would be possible to make the "rock" hollow and to hide an ammunition box inside. Just place the ammunition box on a flat sandy surface and start placing styrofoam around it. Tape and chicken wire are useful to give it strength and to hold everything together. I can stand on my "rocks" without damaging them, but the weight could be an issue, especially for kids. I guess my largest "rock" weighs around 50 pounds, but if you make a smaller one you would probably end up with a weight of 25 pounds. You could make the rock sort of round so kids can roll it over instead of lifting it up.

    1
    shalnachywyt
    shalnachywyt

    3 months ago

    Great instructable! You won second prize! AWESOME!
    When I took an "Art in the Garden" course at my local university, the professor taught us how to do what you're doing. However, we took the meshing used by contractors to adhere stucco to concrete block and used that to cover the foam substructure which we had sculpted into various form. (See pics) The first pic is of the foam cut to show the shape. The last two pics are the final look, including the shallow depression for water to collect so butterflies could have a drink. I had originally painted the whole thing with blue and silver acrylic paint to make it look more like there was mica in the stone, but the paint faded very rapidly. Since then the sculpture has been moved around and a lot of the concrete has fallen off the foam so I have to repair it. (Another thing on my list of things-to-do.)
    I've also been taking those blasted foam containers that fish and meat come in and recycling them into "fake rock" for my "fake" Zen garden. I've been having trouble making them look real but figured since they're probably going to be hidden under bushes and plants it wouldn't matter, except, there are some places where they will be seen. You're solution of doing layers and adding some of that black colorant to get different shades of gray may just be what I'm looking for. I don't cover mine in chicken wire. I just slap the cement on top of the foam containers enough so there's some overlapping. After they harden, I turn them upside down, coat them with a solution of water and concrete binder on the edges, then fill up the void with more broken pieces of foam and concrete. When it's completely hardened I then paint a solution of acrylic sealer on top to help it survive the wind/rain/sun of NE TN. So far, so good.
    I have larger pieces of foam from packing materials that I intend to do the same to.

    Japanese Bench and Butterfly fountain.jpgJapanese Bench and Butterfly fountain 17.jpgJapanese Bench and Butterfly fountain 16.jpg
    0
    s.y.driver
    s.y.driver

    Reply 3 months ago

    Can't wait to give it a try.
    Your instructions are so clear and the outcome awsome.
    Im going for a waterfall rock. Just need to figure out the last coating suitable for running water .

    0
    Liebregts
    Liebregts

    Reply 3 months ago

    Maybe you can try it without coating. Concrete is not fully watertight but if there is styrofoam below the concrete that will not suffer from some water.

    0
    shalnachywyt
    shalnachywyt

    Reply 3 months ago

    The problem was that I needed to have at least a coating of concrete that would be about 1 or 2 inches think all around. I didn't do that. The thickness of the concrete is maybe 1/4 inch at most. Since then I've learned a bit about how thick concrete should be in order for it not to suddenly flake off when moved. Of course, I also should've just found a permanent spot for it and stuck it there and then nothing would've happened, but I sometimes (okay, lots of times!) do stupid things. Right now I'm in the middle of making a 'fake' Zen garden (I say fake because it's inspired by Japanese gardens, but the Japanese would be shaking their heads at the result!) and this piece will be repaired and situated somewhere in this garden area which is about 600 square feet.
    In the meantime, I'm recycling those blasted foam containers that meat and fish come into fake rocks. (see pics) The 7th pic in shows you what it looks like before I've covered the bottom of the fake rock with concrete. The others show what I have already made. I think the 4th, 5th & 6th pics show the top side of those in progress, but with the extreme cold weather, I can't work on it. If you're wondering about the one that has what looks like holes poked in it, there's a simple explanation. I have this work area under my deck and, apparently, when it rained really hard, the water dripped onto the wet concrete and made two rows of "holes". I found it so amusing that I left it. Might give some people a puzzle to work out! I'm just letting the concrete slurp onto the forms with the idea that it might look like lava had oozed out and this was the result. Also, I'm lazy and can't be bothered smoothing it out! (ha ha ha)
    The intent is to eventually have two or three layers of these rocks, but most of them will be under bushes and other plants so they really won't be seen that much. Those places that will be viewed by folks will have real rock laid down.

    Fake Rock from foam (6).JPGFake Rock from foam (7).JPGFake Rock from foam (8).JPGFake Rock from foam (9).JPGFake Rock from foam (10).JPGFake Rock from foam (11).JPGFake Rock from foam (12).JPGFake Rock from foam (1).JPGFake Rock from foam (2).JPGFake Rock from foam (3).JPGFake Rock from foam (4).JPGFake Rock from foam (5).JPG
    0
    Liebregts
    Liebregts

    Reply 3 months ago

    I like the pattern that the rain made.
    Thanks for sharing your experiences and the photos. I am sure you will get a nice zen garden.

    0
    Liebregts
    Liebregts

    Reply 3 months ago

    Your rocks also look good!
    So far my rocks have been in my garden for about 6 months and the concrete has not suffered from the weather. Two and a half years ago I made a dolphin from concrete and there the concrete is also still fine. I made an Instructable about the dolphin too so you can see it in my previous Instructables. Just before the dolphin I made a concrete chicken. It is hollow and the bottom is open and during the summer ants like to live there.

    0
    s.y.driver
    s.y.driver

    3 months ago on Step 10

    Ms Chicken maybe will add some organic color as well to improve the natural appearance.

    0
    Liebregts
    Liebregts

    Reply 3 months ago

    Actually, the only time she ever sat on the rock was when I made this photo. At that moment I put some treats there and she is always interested in food so she jumped on the rock and I could take the photo.

    0
    s.y.driver
    s.y.driver

    Reply 3 months ago

    She is a beauty

    0
    lockstitch99
    lockstitch99

    8 months ago

    what exactly is the "black powder"? the only BP that i know of is used in making fireworks and explosives.

    0
    Liebregts
    Liebregts

    Reply 8 months ago

    It is not that type of black powder :-)
    It is a pigment specific for cement. I found it at a large hardware store.

    0
    lockstitch99
    lockstitch99

    Reply 6 months ago

    oh...sometimes, my mind just fastens onto the too-obvious. also, i enjoy blowing things up.

    0
    shalnachywyt
    shalnachywyt

    Reply 3 months ago

    Are you related to Dorothy "Ace" McShane of Doctor Who? ::smile::

    0
    nedchurch
    nedchurch

    Reply 8 months ago

    Manganese dioxide, it gets very dark very quickly so you need very little.

    0
    austin.hall.129794
    austin.hall.129794

    Reply 8 months ago

    cement dye - can be bought in various shades.

    0
    Suz Ldy
    Suz Ldy

    7 months ago

    I love this instructable! I have a bag of Sculptcrete that I didn't know what to do with, and I'm thinking garden stones would be a great idea!

    0
    Liebregts
    Liebregts

    Reply 7 months ago

    Thanks.
    If you are making several stones, you might need an additional bag. Of course that depends on how big you will make them.

    0
    ellisbrenton
    ellisbrenton

    Question 7 months ago

    Looks Great! One question though - what type of paint did you use? - Oil or acrylic? for the highlights.