Making rocks is easy if you choose the correct material to work with. Rocks made from concrete look extremely realistic and are much lighter than real rocks and boulders. If you are looking for a large landscaping boulder this could weigh as much as 500-1000 lbs where a similar size rock made from concrete will weigh 50-150lbs. Since concrete already looks like real stone, and feels exactly like real stone, this makes concrete rocks the most suitable material for the average person to make rocks from.Https://www.durbinrock.com
Other options for making rocks include plastic materials such as ABS, resin and fiberglass. Much of the faux rock and fake rock industry that exists revolves around products such as this. Fake rocks made from plastic are extremely lightweight and this makes them ideal for shipping purposes. The cost of shipping either real rocks or fake rocks made from concrete is generally too much which is why plastic rocks dominate the retail market. The downside of rocks made from fiberglass or plastic is that they do not look realistic at all. Even from a distance plastic rocks are discernable from real stone and up close they do not look at all like real stone.
Rock Making Stages
1) Make a styrofoam form
2) Wrap in steel reinforcing wire
3) Apply, sculpt and stamp concrete
4) Scrape and wash artificial rock
5) Paint & Seal concrete rock
The stages involved with making rocks involve building a basic form and then adding steel layers which will assist in the concrete climbing vertical surfaces as well as minimizing cracks and breaks in the concrete. The function of the form is essentially to take up space. If the rock were made from solid concrete it would defeat the purpose of having a fake rock since it would weigh close to a real stone. The form can be made out of foam which is lightweight and will not rot over time. The steel is sheets of rolled wire that is wrapped snugly around the form and helps to resist major cracking in the concrete. The steel also acts as a ladder for the concrete to climb and stick to the sides of the form.
The finishing of the concrete is what defines a fake rock as the finish should be textured to be like a real stone and natural faults and cracking should be carved into the concrete for maximum effect.
Using real rock textures and imprinting these into wet concrete in a very similar fashion to how stamped concrete is done will achieve the most realistic look and feel to your fake rock. Polyurethane rubber mat molds made from real rock impressions are the most important tool required in order to make realistic looking stones. Granite, slate and basalt are the most common rock textures with granite easily being the most popular.
Concrete Mix For Making Rocks
A regular bag of concrete mix from a hardware store will not do a very good job at making rocks from concrete at all. A special mortar mix is required that is extremely dense and has a number of concrete additives and admixtures in it to make the concrete creamy, smooth, sticky and extremely strong by comparison to regular mortar mixes.
Other than some of the concrete ingredients and the rock texture mats that you will need to make fake rocks, all other components can be found at most hardware stores. The materials needed for this process are extremely inexpensive by comparison to almost any other type of building material.