Smash and Grab Bowl_Cast Concrete + Glass.




Introduction: Smash and Grab Bowl_Cast Concrete + Glass.

About: I am a qualified Industrial Designer based in Johannesburg, South Africa, and UK Citizen. I currently am working as a researcher, Industrial Design Lecturer, and direct a registered Industrial Design Company.

This is a bowl cast from concrete, utilising glass fragments from one of the infamous ‘smash and grabs’. I am not sure if this is an international term, of if it is mostly understood in my hometown Johannesburg and the rest of South Africa. I have featured this on my website, but I know that Instructables reaches a lot more people/ inventors/ magicians.

If you’ve grown up in Jozi (Johannesburg), you have more than likely seen the extra large glitter sprinkled messily beside your car. If not you, then someone you know. This sadly is not glitter. Rather, it is the cookie crumb trail left by the izinyoka (the snake) to whom you have just donated your car radio/speakers/ anything forgotten on your car seat. This happened one evening to a car parked outside my house. Lurking in the darkness with a dustpan and plastic packet, I collected all the glass fragments as I knew there may be a possible use for them in the future. These remained in a tub on my shelf for many months until I decided to use them as aggregate in a cast concrete bowl. It was a couple months after I made the badass concrete rocket, in which rubber fragments were used as aggregate.

The contrast of the matt, porous concrete and the sharp smooth greenish glass fragments create an interesting visual appeal. This however does not translate into an easily usable product for storing household items... The concrete grit will scratch your phone, or get transported on an apple and end up chipping your teeth.

Even though there are many sharp corners, they get enveloped by the concrete and create a relatively soft form.

What I would like to do next, is use a much higher percentage of glass, which may allow some light to pass through solid concrete. I have seen this online, but it is much easier said than done as concrete is a very difficult medium to 'tame'.



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    23 Discussions


    5 years ago

    Maybe crush up some wine bottles? Maybe some blue wine bottles would look good

    To All

    You may not be aware of this (the instructable author as well!)... So I won't give the initally 'unbelievable secret' away right here but I will give everyone a web site to the French Chemist that discovered this over thirty years ago and has great utility today...I dare say you could make a cup out of this and drop if from 250 feet and not break it... There is a lot on the web site and a book(s) you can buy to learn more about this and to make it yourself... I think that I am going to 'pour' my own house of Granite.

    Here the U.S. Military is using it and there are a lot of great links in the below story too:

    Have fun!!!

    One can purchase hollow glass beads which can be used with the cement in lieu of sand. It can make the cement object semi translucent and can be used to form many types of items. Additionally the glass beads make the material much lighter and have a much higher thermal R value than standard cement. A 6 inch block of cement made with hollow glass beads can pass shadows through the brick in bright sunlight and is rigid and strong enough for a permanent building material. . The University of Alabama built a canoe using this cement mixture with fiberglass and carbon fiber and built a light weight strong and curiously flexible ( the lateral flex actually helped propel the canoe) racing canoe. As the beads are rounded one can create an extremely smooth surface of the cement items. The cost of the hollow glass beads is about 4 times the cost of standard sand but if one is interested in the special properties it is probably better that waiting for your window to be broken for material. Interesting project

    Thanks everyone for all the feedback! I will sift through all my images and try find the photos of the actual moulding process...

    I am familiar with a smash and grab. It happened to me twise and I live in Lancaster Pennsylvania. I am preety sure it was not an amish person though.

    Also cast some concrete shoes for those caught smashing windows.
    Seriously, glass can show off its best with nice cracked edges. There is a special ice like gloss in the edges of a fracture. I like the way you did this more than if the glass was tumbled first. Small pieces of solid copper wire can add to the look as well.

    If you turn this into a proper instructable and tell us how you cast this I will tell you cool ideas how to coat the inside of this bowl with felt, leather or straw. -_-

    Well, this all very interesting but I sure would like an Instructable on how to make these beauties.

    The easiest way to make "Transparent" concrete, that lets light through, is with fiber optic cables, but glass shards might work.

    "Smash and grab" is certainly the popular name for any such property crime here in Memphis. There's also Shoot and scoot, Stab and grab, Gun and run, you get the idea.

    I saw a show at the National Building Museum in Wash DC of advanced concrete and you are on the right track. Concrete is made of rocks, sand and cement. Glass gravel is your rock, and finer glass could be your sand, but portland cement is opaque.. Using polyester resin as your cement gives a product called polymer concrete which would be much more translucent.
    Bowls and sinks like this are cast using big and smaller bowls, which I get from restaurant supply houses or more industrial sources, such as tank head makers. Or, Target!
    You can't really sand concrete. You might do better to rub-in the surface with fine sand and cement mix (wear rubber gloves.)

    here you go, this is based on what some potters use/do to create small windows in porcelain...what they do is press rice into the walls of the vessel. when the bisque fire is done, the rice has burnt out leaving holes. the glaze fills those voids during the glaze fire and creates filled, semi transparent "windows".
    what about using very old, dry bread or toast or crackers...then when the concrete is cured, you can wash out the core making bits and filled with the larger bits of glass that you have...mortar them in place. maybe use small silicon shapes cut our from material or like the cruciform shapes used as tile spacers...carefully push them through, once the concrete has set.

    I like your final product. If you are concerned with "grit" coming off the bowl, just seal it with a food safe varnish. But, this isn't really and instructable, it's a picture, there is no instructing going on. Please describe the process and techniques you used to create the bowl. What was used as the mold? What was the ratio of the concrete mixture? What releasing agent did you use? How did you keep the bowl flat on the bottom? Document with good pictures and explanations.

    Very Niece piece! Granny Jones has a good idea tumbling the glass first to smooth the edges. Although you can still sand the bowl and smooth out the edges.

    When I saw your design and read your comment about using bigger pieces of glass to allow light through, I thought of "See through concrete". I remembered a novel design where they mix clear plastic fibers in the concrete and mold it into bricks. I've included a link so you can see how neat the idea is. You could use a similar technique to make your bowls.

    I would think you could take fishing line cut into short lengths maybe 1.5" to 2" mix it with the concrete - mold the bowl then sand the bowl with increasingly finer sand paper until the fibers a become transparent. Actually you could course sand the bowl to smooth out and expose the ends of the fiber then quickly "paint" the surface of the bowl with a torch. Melting the ends of the fiber, not burning them makes them more transparent.

    Check this out.

    Since it sounds like you are a very frugal person who never waists anything - like we should all be. While searching for the see through concrete I stumbled on this very unique brick design that uses leaves and plastic - I thought it is ingenious - maybe its a material you could use? Keep up the good work, it is a very niece looking bowl!!

    Novel concept for a green brick - interesting choice of material I thought:

    Best regards,

    - Phil

    1 reply

    Found another link here on instructables with a similar design that maybe of interest..


    I would suggest breaking thrift shop colored glass into bits and then tumbling in a rock tumbler to make it look like sea glass.
    no sharp edges.