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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    49 Comments

    0
    Suz Ldy
    Suz Ldy

    5 days 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 4 days 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 4 days ago

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

    0
    Liebregts
    Liebregts

    Answer 4 days ago

    I used acrylic paint because I had a leftover can in the right color. But I think oil based paint might last longer.

    0
    sstorm63
    sstorm63

    4 weeks ago

    Great job, they look so realistic. You should not skip the chicken wire (wire lath). The mortar will shrink and crack over time. The wire helps the mortar hold together and keeps it from falling off of the styrofoam. You can also buy a lot of different color powders that you can basically throw or sprinkle on to the wet mortar and use a trowel or your hands to work it in, just like the mica flakes W2QLH suggested. If you don't like the way it looks, let it dry and apply another coat and try again.

    0
    Liebregts
    Liebregts

    Reply 4 weeks ago

    Thank you for your advice

    0
    LeslieGeee
    LeslieGeee

    5 weeks ago

    Hi Beautifully done, and thank you so much for sharing your process. I too LOVE rocks and your iteration makes them look really real in the pictures. Hypertufa I think can also be made to make rocks if you want them a bit more light weight. Love Ms. Chicken lol. I am wondering about what looks like the cut metal orb on your dry river bed. Did you make it and will you be posting a tutorial on it??

    0
    LeslieGeee
    LeslieGeee

    Reply 4 weeks ago

    Thank you so much for your reply and the info. Not sure if you know about welding but I need to ask. I have never welded anything and read somewhere that braising is similar and easier. I am wondering If I could braise these squares together instead of welding.

    0
    wannabemadsci
    wannabemadsci

    Reply 4 weeks ago

    Hi Leslie,
    You might want to address your question to Liebreats, which I think is about Liebreats steel sphere Instructable. You might even want to ask your question in the comments to the sphere instructable.
    They can reply, but I will share what limited experience I have. I have brazed and welded, both just a little.

    From Wikipedia: "Brazing is a metal-joining process in which two or more metal items are joined together by melting and flowing a filler metal into the joint, with the filler metal having a lower melting point than the adjoining metal."

    Welding uses high heat (and electric arc) to fuse the materials together - melting the base materials. "Welding is distinct from lower temperature techniques such as brazing and soldering, which do not melt the base metal (parent metal)."

    As Wikipedia states, brazing is a lower temperature process where you melt a filler rod between the metals to be joined. It is usually done with a torch and you must heat up the metals to be joined so that the filler material will get hot enough to melt and 'stick' to them. Arc welding is much faster a process as the electric arc instantly melts the materials to be joined.

    I would think that you could braze the squares together, but it would not be as strong as welding and you risk the possibility of softening the brazed joint nearby from the heat of the new joint you are trying to make. Welding would be faster and stronger.

    Good luck!

    0
    LeslieGeee
    LeslieGeee

    Reply 4 weeks ago

    Thank you for the explanation. My last post was for Liebregts because it is still I think attached to my original post to him. I think because you answered that question you will get the additional posts. Sorry about that. I will have to do more research because I am thinking a lighter weight metal might work. Only way to know is to jump into the deep end and try and maybe make a smaller sample sphere:)

    0
    Liebregts
    Liebregts

    Reply 4 weeks ago

    It is not that easy to braze this type of joint. Brazing works best if you have only a very small gap and a large contact surface. The welding I did on the sphere was MIG welding and I think you could do it after just one hour practice. But you need a welding machine and someone who knows how to set up the machine.

    0
    LeslieGeee
    LeslieGeee

    Reply 4 weeks ago

    Thank you so much for responding. I guess this is going on my long list of "how to". That's OK, will keep the grey matter functional :)

    0
    Khovet1
    Khovet1

    4 weeks ago

    Would you please expound on the exact method you used to finish the surface? What smoothing tool(s) did you use? Did you let the concrete dry slightly first? Please help!

    0
    Liebregts
    Liebregts

    Best Answer 4 weeks ago

    I just used my hands (with gloves) to finish the surface. I use the cement quite wet and do not let it dry first. I just very gently and slowly move my hand over the surface. Imagine that you are putting something on the skin of a baby when you are applying the final layer.

    0
    Khovet1
    Khovet1

    Answer 4 weeks ago

    Thank you for your reply. That's very helpful.

    0
    shalnachywyt
    shalnachywyt

    4 weeks ago

    Really nice. I recycle those blasted foam containers that you get from the supermarket that meat and fish come in. Keeps them out of the landfill.
    Although I should cover them with some type of chicken wire (I certainly have enough of that!) I don't. I just slap the concrete mixed with binder, on the foam and build it up to about 2 inches. What I should do is be more careful putting the second and third layers of cement on the form and smoothing it out so it looks like rock and not just a blob of cement. (I'm lazy and in a hurry half of the time.) You're instructable has made me realize I need to slow the process down.

    Every time I mix sand with the cement the end product falls apart after a couple of days. What am I doing incorrectly?

    I have tried using paint to cover the rock and discovered that after about a year, the paint simply fades away, which is disappointing.

    Also: have you tried using the acrylic cure compound instead of water to "cure" the cement the way it's done with cement slabs? If so, what has been your experience?

    Thanks for the instructable!

    0
    Liebregts
    Liebregts

    Reply 4 weeks ago

    I have never used acrylic cure compound, so I don't have experience with that.
    About your problem with adding sand: could it be that you are using a pre-mixed type of cement that already has sand in it? When you add more sand to such a mixture the total amount of sand becomes too much. I recommend that you check the instructions on the bag of cement that you are using to see if they specify that you can add sand or just need to add water.
    Also make sure to mix everything thoroughly.

    0
    shalnachywyt
    shalnachywyt

    Reply 4 weeks ago

    Thank you! It never occurred to me that sand may have already been mixed into the bag. I'll check the bag next time to see if that's the case.