Making T-Glase Crystal Clear

There are 3D printing filaments out there with a lot of interesting properties. Whether it’s the sanded-down MDF feel you get from Laywood, the stretchy and squishy but somehow indestructible feel of Ninjaflex, or just regular ‘ol PLA, there’s a filament out there for just about any use. Even optically clear printed objects. Yes, you can now do some post-processing on printed parts to make T-glase crystal clear.

The big advance allowing translucent parts to be made clear is a new product from Smooth-On that’s meant to be a protective and smoothing coating for 3D printed objects. With PLA, ABS, and powder printed parts, this coating turns objects shiny and smooth. Strangely – and I don’t think anyone planned this – it also has the same index of refraction as T-glase. This means coating an object printed with T-glase will render the layers invisible, smooth out the tiny bumps in the print, and turn a single-walled object clear.

There is a special technique to making clear objects with T-glase. The walls of the print must be a single layer. You’ll also want a perfect layer height on your print – you’re looking for cylindrical layers, not a nozzle that squirts out to the side.

The coating for the pictures above was applied on a makeshift lathe built out of an electric drill and a sanding pad. This gave the coating a nice, even layer until it dried. After a few tests, it was determined lenses could be printed with this technique. It might not be good enough for 3D printed eyeglasses, but it’s more than sufficient for creating windows for a model, portholes for an underwater ROV, or anything else where you want nothing but light inside an enclosure.

26 thoughts on “Making T-Glase Crystal Clear

  1. if you modified the slicer program to leave gaps then pulled a vacuum on the print while it is in a tank of this product you might get a thicker print to be clear. this is quite fascinating Tenneco that i think has some potential to create prints with less grain.

      1. Yeah, dichloromethane is probably above the regular hacker danger threshold too. I thought of acetone or ethyl-acetate cause they aren’t that toxic, but ethyl-acetate would require some heat to get it into vapour though.

          1. Yeah, but it’s worth noting that the auto-ignition temp for dichloromethane is pretty high, while it is pretty volatile and gets to partial pressures high enough to get it to attack the surface without heating it enough to pose a big flame danger.
            Biggest danger is it’s toxicity, but provided that you use a well designed closed system to vaporize it and cold traps to keep it from going into atmosphere it shouldn’t be that trouble.
            But, other solvents are probably better chices.

        1. no exactly what he said under vacuum…it forces any air bubbles that were caught into the solution to be removed as a vacuum environment removes gases from the environment.

          1. A vacuum chamber causes the bubbles to enlarge and hopefully pop. But it also causes the bubbles to dramatically expand. Curing under pressure minimizes their appearance completely.

  2. You would degas your epoxy under a vacuum with its separate parts. Mix it, degas mixture in a vacuum then coat object.

    I used to work in a machine shop where we had to degas compasses for oilfield work. If you put a perfectly clear oilfield compass down the hole that is over 250 deg F bubbles could occur. That is why we vacuummed the solution for about an hour.

    Yes under a vacuum the bubbles will get bigger and pop out of the solution. For the compasses we would pull a vacuum for an hour. Hold the vacuum, seal the unit under a vacuum. There were some expandable bellows to take up the slack space and for expansion.

    If you have never played with a vacuum chamber, you need to. Can be dangerous too…hackers paradise.

  3. I bet this Smooth-On product is nothing more than garden variety clear epoxy given a fancy name. Their Sil-Poxy silicone mold repair goop is only clear GE Silicone II (or similar) condensation cure RTV in a tiny and extremely overpriced tube.

    I bought that once. The cap broke so it wouldn’t seal and the whole little tube hardened. The next time I had a mold tear to fix I just bought a squeeze tube of the GE product for less money.

    The downside to using this type of silicone to repair a platinum cure mold is if you need to cast a new mold part against the repair, any exposed part of the repair will cause cure inhibition. Dunno if that’s a problem with tin cure against condensation cure.

    Platinum cure RTV will not inhibit the cure of any other type of silicone, but most non-platinum cure silicones will inhibit the curing of platinum cure silicones.

  4. The article says this doesn’t work for lenses, presumably because solid infill isn’t optically clear- could you print the outside of a lens like this cup and fill the inside with some clear mineral oil or other liquid with approximately the same refractive index as the filament?

    1. You might as well just print a mold and cast epoxy in it.

      Problem is that good lenses are accurate down to about 100 nanometers. Best 3D printers have mechanical accuracy at around 10-100 micrometers.

      But it could work well enough for something like LED lamps etc.

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