DIY Light Transmitting Concrete (+ HD Video)




About: Travelling since 2013. I'm currently in Australia for some reason. --- I’m Calvin Drews, and I love to learn, experiment, invent, create, repair, and generally just do things myself. A sort of modern jack o...

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I'm going to show you (as best as I can) how to make light transmitting concrete. Google it, and you will be amazed at how beautiful it is! I was desperate to get my hands on some...but considering the cost, I decided to make some with stuff I already had around.

This material has the strange effect of looking shiny or sparkly...but it's dull concrete at the same time! It's very entertaining to show off or play around with.

If this material interests you, check this article out:

Here is the HD video:

Here is the normal video:

Step 1: Making the Mount

 You need to roll some polymer craft clay into a flat circle. Make it as level as possible.

Step 2: Making the Mold

 I cut out a ring from a spray paint can lid...anything that is waterproof will work. After you cut it, press it into the clay.
The whole point of this is to make a mold to cast the concrete into.

Step 3: Fiberoptics

Get one of those plastic fiberoptic toys. They have that sort of 'frill' of glowing wires...see the photo :)
Cut a bunch of small 1 inch segments by breaking off about 10 wires from the bundle, and cutting them short en masse.

Step 4: Placing the Fibers

 Stick the small fiberoptics you cut short (in the last step) into the polymer clay. This may take awhile...but it's kinda fun!

I used pliers. If you use them,too, be mindful not to crush the fibers...they are quite fragile, even though they are plastic.

Step 5: Pouring the Concrete

 I used Rockite Floor Leveling Cement. It's realty just super-duper's more durable and looks way cooler. I even think it's finer grained than plaster (and takes on finer detail. Unfortunately, it doesn't take paint well).

Mix the concrete pretty do not want air bubbles.

Step 6: Breaking the Mold

 Once the concrete is cured (2 hours?) pull off the polymer clay and cut off the plastic ring. The concrete will not stick to the fact, it's practically repelled by it!

Step 7: Trim the Fibers

 After you let the de-molded concrete dry out over night, cut off the extra long fibers. I used finger nail clippers to pick them off :)

Step 8: Polishing

 Use sandpaper to polish your new piece of light transmitting concrete! the effect is quite strange...sort of alien feeling. Light, even colored light, is able to pass right through and create a pixelized likeness on the opposite side...!



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    143 Discussions


    2 years ago

    i made lightconcrete some years ago, but during the polishing it broke the concrete around the fiberoptics... Furthermore the fiberglassstripes came out of the holes... :/ How you fixed this?


    3 years ago

    Many thanks for this interesting project.... The videos are not shown though, can you provide me with a link that I can watch the videos? I really like to watch them.. thanks


    5 years ago on Introduction

    im going to take this technique and make constellations with different shapes and the sort, thanks for the idea


    7 years ago on Introduction

    This is an awesome instructable!  As soon as I saw it, I knew I needed to do a project with this technique.  But what to make? One of my friends owns a concrete supply company, so I put his logo in the concrete. He was very happy to receive it as a Christmas present!

    I ended up having to make this thing twice. The first time, I really messed up the water to concrete ratio on the mix, and when I tried to demold it, it was very crumbly and pretty much fell apart.

    I took photos of the construction of the first one, but didn't photograph the second one until it was complete. I learned quite a few little techniques on the first try that made the second attempt go much easier, so I'll describe those techniques as I go.

    I started with the clay base. Then I printed his logo in black on my HP inkjet printer, cut it out, pressed it onto the clay, then wet the back of the paper and dabbed it a bit with my finger. HP inks are water-soluble, so when you peel the paper away, it's transferred enough ink to see what you're doing onto the clay.

    The second time round, I decided that was still too hard to see, so I filled the design in with Sharpie. This helped a bunch.

    I started putting fibers in one by one with plastic tweezers, but the fibers are so low-contrast that I had a very hard time seeing where they were going and where they needed to be.

    So I used a highlighter to color about the last quarter inch of the fibers, and worked under a blacklight, and I could see what I was doing just fine. The inked part of the fibers ends up in the clay, and it doesn't bother the finished piece.

    I also discovered that an incense holder makes the perfect staging area for fibers, the ash trough makes it very easy to pick them up individually with the tweezers.

    After it was cast (and I fixed a crack with epoxy), I polished it up as best I could on a disc sander (killing 2 discs in the process), and covered it with several coats of triple-thick glaze.

    On one side is random dots of light...

    On the other, a logo!

    2 replies

    Reply 7 years ago on Introduction

    Hey that turned out great! What kind of fibers did you use?

    Oftentimes, crumbling happens because of too much water. In order to get regular concrete thin enough to fill the spaces around the fibers, it's too wet and cures strangely. Rocktite is really magical stuff, you can't add too much water. It pretty much cures no matter what.

    A secret I learned from casting lots of stepping stones is that once you open a bag of concrete, you have to either use it within 24hrs, or put it in an airtight garbage bag and seal it really good. Old, opened concrete will pretty much crumble no matter what you do with it (absorbing water in the air reacts the lime in the micture)

    Rocktite seams to work fine even if its left exposed for a very long time.


    Reply 6 years ago on Introduction

    Oh man, I forgot this comment was even out here!

    The fibers I used were from an LED fiber optic lamp I found at the dollar store. I snipped them to length with scissors.

    I presented this piece to the owner of the concrete business, he really enjoyed it.

    He gave me some tips on working with concrete. Firstly, concrete will always shrink a bit. If you don't want your piece to shrink, use non-shrinking grout mix instead. (he gave me an 80lb sack, yay!) He said it probably crumbled because I put too much water in. The grout apparently doesn't have that problem, you can mix it thinner if you need.


    6 years ago on Introduction

    The most beautiful fiber optic in concrete art I've seen is by the artist Clyde Lynds.
    First saw an example of his work back in '88. Looks like he's gotten more sophisticated.


    7 years ago on Step 8

    just to add a similar idea I recently heard.
    My Cousin is in Peru helping villagers to add sky lights to their huts. They use a clear plastic pop bottle filled with water (clorinated to keep out green stuff)
    It is embedded in the ceiling and sticks out of the roof. It channels sunlight into the hut and apparently lights up as well as a 60 watt light bulb. As long as the sun is shining!

    1 reply

    7 years ago on Introduction

    My friend Karl (KRЯRL to the rest of the world) and I have started putzing around with fiber optics in a fine concrete or mortar. KRЯRL scanned a small relief his friend made from one of his unique figure drawings and had the scan printed into a large styrofoam (polystyrene for the Brits?) negative. The styrofoam served as both a mold for the concrete and a soft substrate to poke the optical fibers into.

    you can read about the process on Karl's blog at:

    1 reply

    7 years ago on Introduction

    Hi, may i know if the following 2 works :
    1) Sticking the fibres into the concrete AFTER pouring the concrete into a mould,
    2) having less space in between the fibres to allow more light to pass through

    Thank you in advance :D

    1 reply

    Reply 7 years ago on Introduction

    I doubt sticking the fiber into the concrete afterwards would work too well, you'd get concrete on the ends and end up with it looking fairly dull, in my opinion. I don't see why you couldn't stick as many fibers in as you want to. Just my opinion.


    Reply 7 years ago on Introduction

    You may want to try to find a book called Sculpting With Cement by Lynn Olson. He uses white cement extensively on the outside of his concrete sculptures


    7 years ago on Step 8

    I think I might try making the "bowl" of a birdbath this way! It might make for some interesting sparkles of light on the ground surrounding it! (hopefully!)


    8 years ago on Step 4

    I must say out of the hundreds of decorative fiber optic devices I have never seen glass fibers used. They would be too fragile.

    1 reply