Large Holey Concrete Voronoi Orb

Voronoi shapes are quite interesting and lend themselves well to the use of concrete. Why not combine Voronoi shapes into the structure of a sphere; a large Holey Concrete Voronoi Orb! Let me enlighten you…

What is Voronoi?

‘A Voronoi diagram is a special kind of decomposition of a metric space, determined by distances to a specified family of objects (subsets) in the space’ as explained by J Smallwood. Look closely as you will see many small odd shapes that come together to create the leaf cell pattern. You know how much I love taking inspiration from nature; and Voronoi in nature is amazing! It’s quite complicated to figure out the geometry but my design is quite simple.

The Shaping:

Before you get ahead of yourself you need to get the shape ready. I’d rather use a deflatable beach ball as balloons can burst and not be so round. When making concrete orbs often covering a ball is difficult since the concrete slides off so here we use a wrapping of poly-twine in ‘Voronoi’ random shapes as an aid for reinforcement. Also add some drywall mess to help to adhere to the ball since it has slight stickiness. Tie and twist as you wrap so that the string does not slide off.

The Concrete Mix

I get many questions about which concrete to use and this mix is my favourite (no affiliation with company) It works easily and cures/hardens fast enough to allow continuous working. Do be aware of temperature and other factors that may dry the mix too fast and always be safe with gloves and dust mask. If you are new to concrete crafting then you may want to check here for some tips.

This mix acts somewhat differently than other mixes but also hardens to a stronger finish. The amount of water needed tends to be less than other mixes as it’s absorbed quickly to make a more ‘plastic-like’ mix. The company recommends adding mix to water; and after using it many times I understand why now; who reads instructions?!

This very part is important; as the consistency of the mix makes all the difference when molding by hand. If you allow the mix to sit for about 30 seconds it will thicken already and become more like a moldable clay. Adjust of it’s too stiff or too runny and only mix small quantities as it will harden before you can use it; I mix about 300ml or so.

Let’s go!

Here’s the fun part… getting a bit messy! As the ball is very stable on a bucket start at the top to keep the weight distributed or it will roll (don’t ask…) Work over a ‘string line’ and across others… Shape the concrete into rolls in your hand and apply, smoothing with your fingers. Since this is a plastic ball the concrete does not stick to it so I do not use any release agent.

Maybe I’m secretly wanting to be a ceramic artist again without the kiln?! This is much like working with clay but a tad quicker. Shape & smooth, add a line, shape and smooth… Slightly rotate the ball as you work downwards. The lacework is about 1/2″ thick

An old brush and water will help take away any lumps and curve the shapes. There are no rules here; and no perfection expected; only that it has enough structure to NOT fall apart. Divide up the larger ‘holes’ into smaller ‘cells’. Once the finished areas are cured/hardened the sphere may be turned to work on the other half

Doodling is very similar; just add as you feel like & keep turning and looking… Use you intuition where it needs more shapes. When adding to areas that are somewhat dry/cured makes sure to spray with water so no cracks happen. Additional concrete can be added later to the concrete orbs if the first layer is well wetted so it does not ‘steal’ the moisture from the new layer.


Concrete likes to be damp when curing. Spray it with water often to build it’s strength and have even curing. This mix will cure to a very strong finish in about 1 hour but you can always give it a bit longer.

Why waste when you can reuse? Deflate the beach ball and pull out of the largest hole of the concrete orb.

Winters in Canada can be crazy but this concrete orb does not have any places to catch water so it fairs really well all year long outside. Ivy will grow through the concrete orbs and it will accent the natural shapes of garden much nicer than the artificial manmade shapes. My theory is that a garden should be about the the natural elements and anything else should follow suit…

Thanks for joining me in my garden and my crazy concrete addiction… IF you want to make more concrete like the large face or other orbs or eggs … concrete on.

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    1. Art in any form is a process; so whatever it takes to make something from the heart & soul is fine… I wish I had a few elves to just clean up behind me. Oh well, sometimes cleaning up does give some new glimpses of how a media works.

  1. THought you might like to know that the link you use for your choice of cement goes nowhere . It says “page under construction” It has been like this for a couple of months now .

  2. Hi Barb! I just wanted to share this with you. Adding simple Vitamin C powder to the water you mix your concrete with will give you up to 10 to 15 minutes to work with your concrete without compromising the strength. I use about 1 tablespoon in 2 quarts ice cold water. Cold water will also give you more working time. I will not pour any rapid set without adding the vitamin c powder now.

    1. Thanks for sharing! I do wonder if it’s the acidic quality that is somehow affecting the alkalinity of the concrete. I also have citric acid that I use for eco printing. I know that when adding some pigment to the rapidset it would change it’s consistency so I have been cautious about adding to it. I’ll be giving this a try soon! Happy concreting

  3. You’re the bomb Barb!! I’ve got 10 centerpieces to make to donate to a fundraiser in June and your ideas really help!! Thanks!!

  4. I have viewed many of your concrete projects and they are fantastic. What a crafter you are.
    Keep the great ideas coming, I love getting messy too.

  5. I love the concrete coasters with leaf design and want to make some for gifts but don’t see them and when I try to go to madebybarb, it says not available. Where do I go to get directions? Thanks. Betty

  6. I love your orbs and I have done some, I have discovered that if you fill the ball partially with water or sand it stays more stable without it starting to turn when you apply the cement. Thank you for so many wonderful ideas (translated by word)

    1. Good idea! It might be had to get water in a beach ball or other ball, balloons it was easier but I hate how they may burst. If you find a proper size base then it will nestle better. It’s all a creative adventure!

  7. Very cool. Thank you for the clear, concise and step by step explanation. I have worked with clay for many years and going to try something like this with clay.

    1. Sure, but I would think you’d skip the rope. I actually started with concrete sculpting since I did not have a kiln and wanted to create things. So many ways to be creative!