A Quick And Easy Recipe For Synthetic Rubies

With what it takes to make synthetic diamonds – the crushing pressures, the searing temperatures – you’d think similar conditions would be needed for any synthetic gemstone. Apparently not, though, as [NightHawkInLight] reveals his trivially easy method for making synthetic rubies.

Like their gemstone cousin the sapphire, rubies are just a variety of corundum, or aluminum oxide. Where sapphire gets its blue tint mainly from iron, rubies get their pink to blood-red hue from chromium. So [NightHawkInLight]’s recipe starts with aluminum oxide grit-blasting powder and chromium (III) oxide, a common green pigment and one of the safer compounds in a family that includes spectacularly toxic species like hexavalent chromium compounds. When mixed together, the two powders are heated in a graphite crucible using an arc welder with a carbon electrode. The crucible appears to be made from an EDM electrode; we’ve seen them used for air bearings before, but small crucibles are another great use for the stuff. There’s some finesse required to keep the nascent rubies from scattering all over the place, but in the end, [NightHawkInLight] was rewarded with a large, deep pink ruby.

This looks like a fun, quick little project to try sometime. We wonder if the method can be refined to create the guts of a ruby laser, or if perhaps it can be used to create sapphires instead.

35 thoughts on “A Quick And Easy Recipe For Synthetic Rubies

  1. https://www.gia.edu/gem-synthetic has some details about the four main ways synthetic stones are made on a commercial basis. Manufacturing techniques like arc and flame formation usually result in crystals that have poor transparency so they can’t support the gain that a laser medium needs. http://www.madehow.com/Volume-6/Solid-State-Laser.html is a reasonable description of how the most common solid-state optically pumped laser media are made, which is pretty similar to how silicon for use in integrated circuits is made.
    I’ve made small quantities of synthetic ruby via the verneiul method. Using an arc is a really neat way to do this and certainly gets a lot larger product than my attempts ever did.

  2. badass! I wonder if they have a true crystollographic axis orientation when made this way.

    I’ve always wondered if arc furnace could actually do this- and it appears so. This is really quite amazing.

    I’ve wanted to make my own ruby from crystal for years for the watch I’m working on- just to say I even made the jewel material itself. This may be a practical way of actually doing that, without buying a crystal furnace.

    I know, the Verneuil method also exists, and should be able to make ruby boules that will crack in two with simple equipment- but this is the simplest functional way I’ve ever seen for doing this.

    I will absolutely be trying this myself now- with other trace metals- to see if I can get definite colors.

    1. You (and pretty much everyone else) are confused. This is a solid mass of microcrystalline rubies fused into a solid mass. Small pieces of aluminium oxide are melted and fuse. They don’t crystallise into a single ruby crystal. Neat, but if you want a single crystal you’ll need to use a more complicated process.

        1. It’s not out of the question. Don’t they make huge sapphire crystals for SoS wafers and other applications? Looks like you can buy a 4inch sapphire wafer (0.65mm thin) for about $50.
          (natural rubies have never been large enough (or perfect enough) to make laser rods out of, have they? (despite assorted spy/scifi movies.))

          1. We made a lot of wafers (six inch at the time but much larger now) out of our standard sheet stock. We also made electrostatic chuck from wafer sized sapphire. Some reasons, sapphire has very high resistance to high voltage in thin sheets, it doesn’t shed particles and is lighter than standard ceramic. I silk screened the conductive material directly on the back side of the chuck.

      1. Yes, I was tired and too astonished to see the full process.

        Unfortunately HaD has no edit or delete button. I quickly realized its a fused mass of polycrystaline ruby, not a usable material for bearings.

        Should still work to make ruby files and stones for stoning perhaps, once the shell of the the mass is ground away.

        Back to saving for a crystal furnace.

    2. I’d read into semi-conductor material manufacturing to gain some insight into what is needed to produce desired effects. I’m no way an expert at this… though have done some micro testing on metals in my earlier carrier with a little later study and hands on crystallization for synthetic and crystallography methods (impressive skill). Mono-crystalline materials manufacturing is an art and science in itself too.

      In regards to the mono-crystalline materials… maybe this wiki will gain some insight for starters:
      https://en.wikipedia.org/wiki/Monocrystalline_silicon

      I’m not sure of a good video reference regarding the history of manufacturing to gain some more primitive techniques insight… though I did watch this series recently that details at times processing materials methods and development:
      https://www.youtube.com/channel/UCzGJnKGMwUpm7_P6Y0UwTaw/search?query=A+video+history+of+Japan%27s+electronic+industry

  3. I worked for Saphikon, a company now bought out by Saint Gobain for 12 years. My job was to invent new process gear and control systems for our crystal pullers. We grew tiny fibers hundreds of feet long used in ceramic parts for spacecraft engines, large sheets (12 inches wide, 3/8″ thick and 15 inches long and everything in between. We also grew sheets used in supermarket scanners since sapphire is so hard that it can’t be scratched by ordinary items. Semiconductor manufactures used sapphire in their processes because it doesn’t shed particles and is resistant to most acids.

    We grew sapphire from molybdenum or tungsten crucibles heated in induction coils in an argon atmosphere with the melting temperature of 2200 C. It was edge defined growth meaning the crystal would take the shape of the die. The seed, slowly lowered to the top of the die determined the orientation of the crystal, C plane being the usual but also M and A plane for special projects. Growth speed varied from 4″/minute to 0,5 to perhaps 4″/hour for the larger sizes. Temperature control was with non-contact, two color controls made by Ircon.

    For most of the growth systems, we would replenish the crucible with more feed material to keep the level constant. I made many of these feeders using weighing systems to keep everything balanced. I used PLC controls for everything but later converted over to PC computers to handle all the other variables.

    The sheets came out with an uneven surface, later polished with Blanchard grinders to get an optically flat crystal.

    All I have time for now but I can answer questions if needed. It’s been a while since I left, but that hard-won knowledge sticks.

    1. Thanks for the informative anecdote of real world creation. Confirmed a lot of things I suspected would make better crystals and some of the right technical terms for further research.. Also damn you, now I feel even more inspired to give it a go at some point!

    2. Been wanting to do this (ruby laser rod) since the early 70s as a kid. Do you by any chance recall the induction coil frequencies and ~currents required (given a certain size crucible I expect)? I also got stuck on determining crystal planes, but I suppose you buy a small piece of laser rod as a seed.

    3. I would buy you a case of beers to pick your brain on this.

      Any idea what make of furnace was?

      How much for crucibles? Any idea? It’s been hard to price these, and I’ve seen iridium crucibles used as well.

      What mesh size and purity was your starting material?

      Any idea if they did custom colored melts?

      So many questions probably too proprietary or nda controlled to answer…

    1. Yes, long familiar with them.

      To be clear- before my stupid was showing-

      Getting material to make my own jewel bearings was never the problem. As you can see, you can buy a lot of that off the shelf these days.

      Hell, I even have a half of ruby boule from a Verneuil furnace here right now, solid crystal. Buying them is cheap, and good quality watch jewels can be made from it.

      I specifically wanted though a specific color for my jewels not commercially available, and in a hue concentration I control- so the hue when cut to thicknesses I need stays controlled. I wanted a Czochralski method boule for optical clarity- but they don’t do specific colors with that method, as that’s mainly for industrial uses. And its extremely expensive to buy boules made with that method.

      Practically, I’ve seen Czochralski method furnaces sold in the 20k$ range for small college laboratories before. A Verneuil furnace is probably more doable, but then you can’t control the orientation of the crystallographic axis that way for putting the hardest axis in line with the bearing surfaces for extremely wear resistant bearings, though that may not matter that much.

      Would love to see an article on building a working Verneuil furnace- I think that is actually doable at home- though dangerous- there are plenty of them running in rural India making gem material everyday.

  4. OK, a few questions to answer.

    Power to drive the induction coils ranged from 25 Kw to 250 Kw, input power 480 volt, 3 phase. Frequency was 9.6 khz, chosen to be below the frequency where the FCC (I think) restricts radiated power. We were working right up next to these systems so biological considerations were also a concern. Being too close when trying to see through welding glass filters would cause a sharp pain right between the eyes.

    The furnaces were made by local machine and welding shops who were rated competent to make vacuum equipment. Process included electro-polishing all interior surfaces to minimize oxygen retention. Any oxygen at those temperatures would quickly oxidize graphite insulation and other parts. We had to pump the chambers down before bring the temp up before turning on the argon gas.

    The feed material was boule ends imported from China and Switzerland where they grew sapphire to use in watch crystals. We would get the shipments in 100 KG barrels. Each shipment had to be carefully inspected to make sure that contaminants wouldn’t ruin our clear crystal products. We used UV light that would cause unwanted bits to glow. We would then crush these boules to the consistency of beach sand. I don’t know the mesh size although we would screen to get constant feed in my vibratory feeders.

    Since we were pushing a LOT of power through the 1/4″ to 1/2″ coils, they were all water cooled with deionized water. Other parts like the stainless steel double wall chambers were also water cooled. We had two cooling towers outside to get rid of this heat. Long distance focal length microscopes with proper filters were used to visually monitor the placement of the seed(s) and the growth process. Our technicians were very skilled at keeping the process stable.

    Knowing what I know, I wouldn’t recommend anyone trying this at home. I’ve done some crazy things including a microwave vacuum chamber to dry green turned wooden bowls, very impressive to the layman with all the extra instrumentation I’ve put on it but as far as I know, only the truly obsessive would go to those lengths. Sure is fun though but no ways near the potential for death as what I worked with before.

    1. Thank you for so many details you cared to share. The electropolished furnace interior makes sense, and was never something I knew of.

      Yes- honestly, a Czochralski furnace is not possible in a house. 480 3 phase I use I use at work powering EDMs- yes- would be crazy expensive to even get the power company to wire that to my house, transformers alone for equipment are a few feet square.

      I think, though highly dangerous, a Verneuil furnace would be doable at home, as I’ve seen pictures of the original furnace from 1904. Its not a large object, would be perfect for my needs- but hydrogen gas is extremely extremely dangerous.

      would definitely have to be done outdoors away from a house in a ventilated structure- far from living beings. Still, extremely dangerous. Darwin award waiting to happen. I’d still try it though.

      People like you are why I read Hackaday.

  5. Not personally interested in the jewelry applications but would it be reasonable to start with this process, add some machining and create a 3d printer hotend?

  6. I cringed at 3:35 when he used the welder on the powder on the plate. Having super-hot ruby blobs flying everywhere is pretty damn scary and completely unsafe. Could’ve burned down his shop. Not only that but you should always wear some kind of particle mask when handling any kind of powder like these. You really don’t want to breathe in this stuff even if it’s “not toxic”.

  7. Hello everyone
    My nickname is axonf. This tutorial is about the production of a ruby crystal is very interesting. There are two ways to get a high temperature of about 2000 Celsius degrees to melt aluminum oxide, that i tested. The first way is an induction heater with a special coil and in the middel a molybdenum melting pot. The second way is an electric arc supply with a small molybdenum melting pot with a cover. You experience something about my composition in the german forum mosfetkiller under sintern und schmelzen von Aluminiumoxid mit Induktionsheizer. Habe a nice day, axonf

Leave a Reply

Please be kind and respectful to help make the comments section excellent. (Comment Policy)

This site uses Akismet to reduce spam. Learn how your comment data is processed.