How to Make Fake Rocks with Concrete
from wikiHow - The How to Manual That You Can Edit
Making fake rocks is a fast growing hobby and profession. Combining basic construction skills and artistic creativity you
can create artificial rocks with concrete that are virtually
indistinguishable from naturally occurring stone.
Fake rocks are quite inexpensive to make yourself and if it turns out
that you have an eye for sculpting you could find yourself in a new and
profitable profession. From small stand alone stones like an address
marker to a grotto covered hot tub or rock retaining walls or better
yet –rock-climbing walls, artificial rock has many practical
- Building a form - You will need to
use a form to build your artificial rock since concrete is very heavy.
Make the bulk of the size of your rock from foam and cover with
concrete at a thickness of 2-3”. This will make an artificial
rock that feels and looks very real while being much lighter than real
stone. You will need to wrap the form in chicken wire and steel
reinforcement mesh so the wet concrete will have something to cling to
on vertical surfaces and to provide overall cohesive strength to the
- Mixing concrete - This is done in a bucket by hand or with a point trowel, or in a wheel
barrow with a pointed shovel, OR on a piece of plywood with a square
head shovel OR in a cement mixer. These options are listed in order of
smallest to largest batches of concrete needed. Mix 3 parts fine grade
clean, washed sand with 1 part type 1 (also known as type 10) portland
cement. For additional strength you can add glass fibers to your mix in
small quantities. Wood glue, fly ash and silica fume are also used for
professional level rock sculpting. Add water to a thick paste and mix a
very, very long time before using. If your muscles are not burning you
have not mixed it enough
- Sculpting the concrete - Use a point trowel to sculpt the concrete after applying to the form. Become
familiar with how rock formations look and plan to be patient.
Sculpting rock is a very marketable skill and takes practice to achieve
- Texturing the concrete - Use a sea
sponge to create a pock marked, weathered effect. Texture mat imprints
from real stones will drastically increase the cosmetic value of your
rock. Nothing looks more like real stone than an imprint made directly
from a real stone. Texture mats will also help to provide inspiration
for the sculpting process as you can continue the veins by hand past
the edge of your texture mat impression.
- Curing the concrete - Concrete
takes a full month to cure and is about 75% cured after the first week.
If the rock is left to sit in direct sunlight during curing stage
hairline cracking will be excessive. Soak with water often to minimize
hairline cracking and proper curing.
- Scraping the concrete - Wait a
minimum of 3 full days of curing before commencing this stage. More if
you are not in a hurry. Using a fine grit scraping stone grind the
entirety of your artificial rock to remove rough edge that concrete has
to the touch. When finished your rock with be smooth just like real
- Washing the concrete - Wash the
rock thoroughly before proceeding to add color. Use a stiff (but not
wire) brush to clean concrete dust out of all the nooks and crannies as
this will look unsatisfactory later. Dry completely before coloring.
- Painting the concrete - Using
spray bottles and water based paints you will mist multiple layers of
complimentary colors over and over again to create a deep and realistic
rock color. Inspect real stone closely to learn what colors produce
which effect. Common upon close inspection of real rock are blue,
green, red, orange, yellow, brown, etc. The higher quality your spray
bottle system, the better your finished results. Ideally you should be
able to gently mist each application of color without any blotching.
- Sealing the concrete - Use water
based concrete sealant and apply 3 layers allowing time to dry
completely between. Reapply once yearly via spray bottle to retain
- Lots of warnings. Beware of power tools,
concrete mixers and heavy construction. Proper safety attire and work
habits are required. Safety glasses, protective gloves, cartridge
ventilators are an absolute must. Concrete contains Quick Lime, a
strong alkaline substance that can cause chemical burns on exposed
skin…imagine what it can do to your lungs or eyes.
- Do not attempt to build anything bigger
than what your skill level allows. Features like ponds / swimming pools
or rock-climbing walls can be extremely dangerous and you should not
attempt to build items like these unless you are sure that you have all
the required experience to do so.
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