Making fake rocks using cement
There are many different ways of making fake rocks.
They can be made with plastic, fiberglass or cement
mixes. I prefer making my rocks from cement. Cement will
be a little heavier than plastic or fiberglass, but they
make up for it in looks. Also known as artificial rocks,
faux, imitation or man made rocks.
An artificial rock can be made any size or any color.
They can be used for covering unsightly features in your
yard such as wells and gas meters. Most are made for
decorations or for waterfalls. You can have a rock
feature that drains into your pool or have a living
rock. A living rock simple has a pump underneath that
pumps the water to the top. The water then splashes down
the rock into a reservoir.
You must first figure out the size, shape and if you
want it hollow or not. Another thing you may want to ask
yourself is if you want any lights or plumbing for
water. There is a few ways you can start your project. I
like to use cardboard boxes then wrap it with lath
(chicken wire) to mold the basic look of the rock. If
the rock is going to need lots of strength, you may want
to weld a metal cage or built a wood frame, then fill it
with boxes. This is only necessary if you are going to
walk on it or it is going to be supporting something.
Some people prefer to use big chunks of styrofoam, then
shape it. I find solid styrofoam to be expensive and messy.
Once you have the basic form of your rock made, you
will need to apply a thick coat of a mixture of
styrofoam balls, portland and sand. I don't know the
exact ratio of each. You will have to experiment a
little to figure it out. Start with the styrofoam and
add water and portland, then add the sand. You will want
the mixture to have a consistency that will allow you to
shape and form it. An additive called calcium chloride
or concrete excellerator may be added to speed up the
drying/curing time. (Don't add too much) If you don't
want to try mixing your own you can purchase it already
mixed (just add water) from other places on the internet.
As the project begins to dry you can shape it further
with carving tools. Giving it more definition anything
from a spoon to a mason trowel will work. The longer you
let it dry the harder it will get. So try and get to it within 24 hours.
Once you have finished shaping your piece it is time
to apply a thin layer of concrete. The concrete mix will
be made from white portland, water and white silica sand
50-60 mesh seems to work the best. This mixture can also
be bought in a bag (just add water) from concrete
resurfacing suppliers. Make sure you use white portland
if you plan on mixing your own. So it will stain
afterwards. This mixture can be colored to create a
solid color. For example if your rock is going to be
dark in color you should mix the cement a couple of
shades lighter than what you want your final piece to
look like. Then when it is dry, you would have to add so
much color stain to it. Once you have you color mixed,
simple scoop up some in your hand (use rubber kitchen
gloves) and rub all over your piece. The thickness all
depends on you, you can leave just a thin layer to give
it a smooth look or you can apply a thicker coat (1/4")
then use a texture mat to give a different look. If you
don't have a texture mat you can anything for a rag or
garbage bag to give it a different look.
Staining or coloring can be done with concrete stains
or using concrete acid stains. Both of these ways will
take some practice in getting the look of a real rock.
For example use a paintbrush to darken areas.
Use a concrete sealer to finish off the piece and to
protect it from stains and the elements. Apply with a
brush or spray it with an airless sprayer.
It is always a good idea to attend a seminar or class
on how to make rocks before trying to make your own
rocks. This way you will practice with their supplies
and pick up on tricks of the trade.