Instructables

Step 2: Mix concrete, fill your mold...


Spray your mold with cooking oil and set aside. Mix the concrete so it is about the consistency of peanut butter, not a slushee. It should hold a bit of form when shaped into a ball, but not so wet that it slumps, and not so dry that you can't make a ball without a great deal of effort. Not too wet, not too dry.

Pack the mold, tapping and poking the concrete down into any crevices in the mold. Once filled, level off the top with something flat like a ruler. If you can, carefully bounce the project on a firm surface that is covered with something cushy. You don't want to break the mold, especially if you've chosen a glass mold.

Set on a level surface out of direct sun. Wait twenty four hours before you even think of touching it.
 
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Livy Apple3 years ago
but ...
it may occur that chicken wire can get rusted... and isn´t it bad for gardening?
even if chicken wire doesn´t have direct contact with roots, oxide can pass through concrete mix (hypertufa) and damage the plant!!? opinion?

BrianJewett3 years ago
What about reinforcing materials like chicken wire or some sort of fiber? Will the bowls be strong enough without it?
WUVIE (author)  BrianJewett3 years ago
Hello Brian,

As these bowls are relatively small, I don't know that reinforcements
are necessary, but certainly a good idea just to be certain. Especially
if the bowls are going to be used outdoors.

Many thanks for the mention of wire or fiber!

:-)
jsadler1 WUVIE3 years ago
I like to use chicken wire in any project just to save the occasional foot from being crushed. It is not always that the product will ever be stressed in use but having a bowl snap in half while moving it can make a mess out if a foot. And anything that could ever involve a falling chunk of concrete absolutely needs wire or rebar for safety. A few layers of chicken wire can boost the strength of some cement-sand mixes to astounding strength and without need for rock in the mix capturing detail in a mold is rather easy.
WUVIE (author)  jsadler13 years ago
Chicken wire, oh, and we have plenty of that around the house. Can't wait to try my next project using reinforcements.

Thanks for your post! :-)
glorybe WUVIE3 years ago
Several layers spread a bit apart can build a very strong structure. Everything from ships to roofs that you can park cars on has been built with layers of cement and chicken wire but you want to apply the cement all at once. A common toilet plunger can be used to make the cement mix spread nicely through all the layers of wires. Some people make little poker chip like objects from cement-sad mix to keep the wires spread apart. With good sand a mix of 15-20 percent cement will get the job done. Remember that wires replaces the rock found in concrete so you want to have about five layers of chicken wire for two inches thick finished product and always mix with as little water as you can and still work the mixture into the forms.
outdoorart3 years ago
Concrete reaches something like 90% of it's strengh in 3 days...the last 10% is complete after 30 days....in construction work, forms can be removed in 3 days.
It is a chemical reaction so the right proprtion of water to cement is important. You don't want this water needed for the chemical reaction to evaporate, so it is good to keep the surface moist (or at least not dried out). Cement is not an environmentally friendly material so substituting portions if a different material is a good idea. You can experiment with sand, soil small rocks, ground glass, etc.
Thanks for posting...this is a great project and your bowl is beautiful.
WUVIE (author)  outdoorart3 years ago
Great information, Outdoorart, thank you so much for your compliments and input! :-)