Transparently-thin Granite LED Lamp




About: I'm a guy with diverse interests in San Francisco, CA. I enjoy solving problems, inventing and making things, exploring the unknown, making music, and learning new skills. Learn more about me at gordonki...

I got a beautiful piece of rose granite from construction junction here in pittsburgh, and noticed that it appeared to have such clear quartz crystals in it that it might transmit light if cut thin enough.

I cut some wafers on the water jet, and indeed, it could be cut transparently thin!

I set out to see if I could make a monolithic (truly "of a single stone") LED lamp, which had LEDs in cavities cut WITHIN the stone, shining out of transparently thin walls.

Step 1: Determine How Thin You Can Cut Your Granite Before It Falls Apart

It is important to experiment with your particular material. Granite is brittle, and comprised of different crystals (feldspar and quartz, mainly) that can be broken apart from the incredible pressure of the water jet. The cutting behavior probably will vary between types. It also often has cracks. When 60,000 psi water finds a crack, it will inflate it, and your stone may split. This is an unavoidable risk of working with stone in general, and especially with pressurized water jets, so moderate your expectations, and be prepared to tolerate some breakage.

My granite was 1.25" thick. I made a series of cuts across a small bar of material to evaluate cutting parameters. Obviously, cutting at the slowest tolerable speed will give the highest quality / smoothest cut face. I got great smooth texture on the 1.25" deep cuts at settings that produced 1 inch per minute. You might not be able to tolerate cutting slow though, because water jets are expensive to operate. Techshop Pittsburgh charges $3/minute. You may find a commercial shop to do the job cheaper than you can do it yourself at such rates, as my friend did with one of his small jobs. (The convenience of designing and cutting something within the same hour though is wonderful, but inflated operating costs like this definitely inhibit extensive experimentation).

I successsfully cut wafers as thin as 0.10" thick which were nicely transparent. You can certainly cut wafers even thinner than that, but I was satisfied with this thickness.

The greatest challenge with cutting small parts on the water jet is preventing the part from falling into the water jet pool. The water jet's pool (at least ours at Techshop Pittsburgh) is a murky abyss which, though only 30 inches deep, is effectively bottomless, as regards the irretrievability of things dropped in. The support grid resembles a portcullis of pestilential rusty dagger blades pointed upwards, and the tank's contents include a thick mud of powdered garnet and cutting debris, with a dubious ecosystem of microorganisms subsisting on this curious brew. Because the water jet cuts through *everything* - including it's own table - it can be difficult to not lose small parts when they are severed, and pressed down by the pressure of the water.

To prevent losing your part, you can do several things:

  • support the part on a thick stack of plywood - 2 or 3 inches thick. The part is cut normally, and as it is severed, the wood plugs cut beneath it tend to jam, preventing the part falling through. Also, the wood blocks float, further resisting the part falling through (presuming your water level is high enough). Also, the water jet beam diverges and warbles downstream, and if the wood is thick enough, it will sometimes preserve a network of connections between the plugs and the surrounding wood, supporting your part.
  • you can also hot glue a string to to your part, taking care that the string does not get severed as the contour of the part is cut.

Step 2: Design Your Granite Cross Section

I opted to make a triangular lantern cross section, because I could have thick corners with holes for threaded rods, with a flat on which I could attach LED strip, and the LEDs would shine onto the opposing flat faces. Any odd-number-of-sides polygonal cross section would have that property, but a triangle is the simplest odd-sided polygon. Attached is a .DXF file of the cross section of the lamp I made.

Step 3: Waterjet Cut Your Cross Section

Step 4: Affix LED Strips to Flats Within the Lantern and Wire Them Up

Three one-inch cut-lengths of LED strip were adhered to flats inside the granite, wired in parallel, and energized.

Step 5: Use Threaded Rod to Hold the Lantern Segments Together

At least, I intended to use threaded rod. However, the water-jet cut holes were not smooth enough to admit threaded rod. They were still able to be laced together with string.

That completes the project. I'd love to experiment further with water-jetting granite though, and in particular I'm excited to see if I can pierce larger thicknesses, with a five axis water jet, and make fire sculptures consisting of stone through which gas ports have been bored.



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    17 Discussions

    I will never attempt your project but for some reason I read the paragraph beginning: "The greatest challenge...". The vision you created with that was riveting. Your descriptions are so clever, vivid and animated with the vocabulary you employed. It almost stands alone as a work. Thanks, Michele

    1 reply

    I'm sure I'm not alone in being inspired to poetry by the waterjet:-). I wasn't sure if such florid imagery was appropriate, but thought to myself "what the heck, indulge". Thanks for your appreciation and encouragement!


    3 years ago on Introduction

    Poetic indeed! Congratulations on the Pier 9 Residency as well. This piece reminded me of one of my favorite buildings, the Beinecke Rare Books & Manuscript Library at Yale. They protect the books from sun damage by using a thin translucent stone skin for the facade. It looks monolithic from the outside but warmly radiant on the interior. Great collection if you ever have the chance to visit.




    4 years ago on Introduction

    Such a beautiful effect. I would love to see a larger build in the future. You are very lucky to have access to equipment capable of this kind of cutting :)

    3 replies

    Reply 4 years ago on Introduction

    I agree, it is a beautiful effect. I would also love to see a larger build in the future. Perhaps if I get the Pier 9 residency I can use a less(?) expensive, more capable waterjet to experiment with this technique at greater length. You might also have access to this kind of cutting, if you live near a maker space that has a waterjet. Techshop now has 8(?) locations?


    Reply 4 years ago

    Woohoo! I got a golden ticket to be an artist in residence at Pier 9, so I get to use a 5 axis water jet (and much more) at no cost! Stay tuned for much more ambitious experimentation!!


    Reply 4 years ago on Introduction

    Oh my! Congratulations! What an amazing opportunity - you deserve it! Looking forward to seeing more from you soon :)


    4 years ago on Introduction

    Maybe if you bond the stone veneer to a clear substrate like a sheet of plastic it would be easier to work with and still retain the light transmission properties. Light up stone marquetry/stained glass designs would be cool.

    6 replies

    Is stone veneer a thing? I puzzled over the practical challenges of cutting large areas of brittle hard stone to veneer thicknesses. Can you point me towards where to source it, or how it is made? I know it can be simulated, as my clients Forms and Surfaces, and Vivid Glass, have a business making multi-layered images within laminated glass.

    Most home centers have a stone "veneer" so you can recreate a faux brick or massive stone mantlepiece. That would be construction grade and relatively thick and opaque. I think you are on to something though. I believe they used sheets of mica in some architectural things like lamps or door glass/sidelights, maybe from the craftsman era/ Frank Lloyd Wright. You can probably also float a layer of resin to reinforce a cut piece or even tape on top if you plan to embed it in mortar or apply it to a surface. The potential is there for light up bar tops and art pieces.


    Oh, and even wood veneer is sometimes pieced together or patched in. The same techniques used in composite countertop fabrication would work like using the stone dust and resin to fill in or connect the pieces.

    now there's an idea. You could cast a thin layer of stone dust and clear resin to make thin sheets that might have nice properties. I also like the thought of using Mica, but where nowadays does one find large slabs of mica...

    Try slicing some sample pieces of Corian or those other branded composite countertops to see if they have translucent properties. You do find some cheap "slabs" by getting cutting boards made from smaller pieces.


    4 years ago on Introduction

    Nice. Maybe you could try putting the LED strips in a triangular column in the centre (LEDs pointing outside of course) so there will be no dark bands on the stone.

    No, if I had only access to a water jet cutter...

    1 reply

    Reply 4 years ago on Introduction

    I thought about putting the LEDs on a column in the center, and having simply a granite thin walled cylinder surrounding them. I'd like to try that if I do this again. You might have access to a waterjet if you live near any of the techshop locations. Where are you based?