Tutorial ~ How To Make a Hollow Concrete Sphere

• Inflatable ball

• Large and small bowl to mix concrete
  

• Gloves
  

• Dust mask
  

• Vegetable oil spray or petroleum jelly

• Large pot to support ball

• Large trash bag and tape to cover sphere

• Paper towels

• Spray bottle filled with water

• QuikWall Surface Bonding Cement

• FibaTape for Cement Board

Cement and fiberglass mesh (FibaTape) are the two major components used to create a hollow concrete sphere. The information I've compiled regarding these two components is always the boring part of any presentations I've given. I know you're anxious for the instructions to make a hollow concrete sphere, so I'm not going to include this information in the tutorial. However, I'd like to share what I've learned and will post a "Technical Info" thread for anyone interested in the specific cement and fiberglass mesh I've chosen to create my spheres.

Day One:  Gather all materials before starting

• Cut 6"-8" strips of FibaTape and set them aside.

• Fill bottom of large pot with rocks or sand for weight

• Confirm ball is fully inflated and set on pot with inflation tip down.

• Cover exposed surface with PAM or Vaseline

• Determine how large an opening you'd like for the sphere (red dotted line indicates the size of my opening)

• Apply FibaTape strips to the exposed surface, making sure to overlap each strip

• Wearing gloves and dust mask, measure 6-8 cups of QuikWall into the large bowl. Avoid making the most common mistake of adding too much water. Slowly add small amounts of water, mixing after each addition.

When your mix is the consistency of peanut butter you're ready to apply it to the mesh covered ball. If your mix is too wet (soupy), small amounts of QuikWall can be added to achieve the desired consistency.

• Take a handful of the cement mix, make a pattie and use the palm of your hand to apply to the ball surface. For lack of a more sophisticated description, "smoosh" the mix into the FibaTape until it completely penetrates the mesh. Continue this process until the entire surface is covered with a thin layer of cement.

Don't be concerned if the surface isn't "smooth as silk" because you'll be adding two more layers of cement.

• Loosely cover the entire ball with a large trash bag. Gather the ends of the bag around the base of the sphere and close tightly with tape to eliminate any gaps. Leave for 24 hours

Day Two:

• Repeat the process of cutting more strips of FibaTape and mixing cement.

• Using the small bowl, take 1/3 of the cement mix and add more water to create a soupy mix, i.e. "slurry".

• Remove the trash bag and cover the entire surface with slurry.

• Repeat the steps for applying the FibaTape strips and another thick coat of the cement mix.

• Lightly spritz the surface before loosely covering the ball with the trash bag. Secure with tape and leave for 24 hours.

Day Three:

• Mix more cement, again dividing 1/3 of the mix to add water for slurry.

• Apply slurry to the surface. (This time it won't be necessary to add another layer of FibaTape.)

• Add one last coat of the thicker mix and spread over the entire surface. This will be your final layer so strive for a smooth finish before covering. Cover again and leave another 24 hours.

Day Four:

• Remove trash bag. Rotate sphere to expose opening and place it back on the pot for support. 

• Carefully cut away and remove any excess FibaTape before deflating the ball.

Slowly deflate the ball. Remove the ball when it is completely free of the interior wall.

Once the ball is removed mix more cement to smooth the rough rim of the sphere.

• Mix small amount of cement and slurry.

• If you discover tiny cracks on the interior of the sphere use an old paintbrush and 'paint' the cracks with slurry before working on the rim.

• Work slurry into the rough edges of the rim and then apply cement to form a smooth, rounded edge.

• [Optional] For additional reinforcement bend poultry mesh around the rim and cover with FibaTape before applying the slurry and cement.

FYI: I'm always asked how I achieved a "flat" edge on the rim of my sphere. (Note: this option requires at least one additional day)

• Pieces of wire (hardware cloth) were cut to form the desired opening. Thin wire was used to connect the pieces and hold them together before applying more cement.

• Cover with trash bag and secure tightly with tape to form an airtight seal. It's recommended to wait 30 days before painting or staining and sealing to waterproof the sphere. If you're experiencing really hot weather you may want to uncover the sphere daily and spritz with water to prevent the cement from drying too rapidly and then cover again.

*Keep reading to learn how you can finish in just one week!

Painting:

Any exterior latex paint can be used. Patio paints, which are recommended for painting terra cotta pots, are a popular choice because they don't have the tendency to fade in the sun.

Acid stains are another popular choice because they have the ability to create truly unique finishes resembling aged concrete or copper patina. The specific formula used for these stains etches itself into concrete and provides a durable, long lasting finish without fading. However, they're somewhat tricky to use and fairly expensive.

I had hoped to simulate the look of granite with a flat latex paint on the textured surface. The gray base coat failed to meet my expectations, so I added an additional coat of 'faux stone' spray paint in order to achieve the look I wanted.

Sealing:

It is necessary to seal the exterior and interior of the sphere. It's also recommended that you re-apply sealer at least every two years to prolong the life of your sphere.

While any waterproofing sealer (i.e. Polyurethane, Thompson's Water Seal, etc.) may be used they merely form a coat on the sphere and won't provide long lasting protection. It's highly recommended to use a penetrating sealer specifically designated for concrete or masonry. These water-based acrylic sealers are paintable, penetrate the concrete to form a bond with the cement, and actually promote the curing process by retaining moisture.

* Good news! Your sphere can be ready to display in your gardens in just one week! Because penetrating sealers can be applied to fresh concrete you don't have to wait 30 days to paint your sphere. After curing a week the sealer can be applied (preferably two coats) and you're ready to paint!

Most sealers dry within two hours so it's possible to seal your hollow concrete sphere with the recommended two coats quickly and apply your choice of paint all in one day!

That's all you'll need to make your own hollow concrete sphere! Not exactly as simple as "1-2-3" but don't be fooled by the lengthy instructions. It's really a piece of cake! Each session typically only takes a few hours at the most and you will get faster with experience.  I was a total "newbie" when I tackled working with concrete for this project and I'm positive you'll be successful as well! All you need is a block of time, a few materials, and in one week you can have your very own hollow concrete sphere to display in the garden. Let your imagination run wild and create your own unique touch with decorative accents or plant your hollow concrete sphere to use as a water garden!

As promised, I'll post an "Info" thread for anyone interested in the technical aspects of the cement and fiberglass mesh chosen for my hollow concrete sphere.