Looking for a material that:

  1. Is transparent/clear - the clearer the better
  2. Can be made to about 80cm long x 8cm wide by somewhere between 2-5cm thick (likely 2-3cm, exact details will depend on the material's properties)
  3. Can be shaped on the cross section, either during manufacturing, or after
  4. Is at least a bit flexible - I'd estimate no more than 20 degree bend along the length, without too much force required - i.e. something that could be bent by hand, like a plastic ruler.
  5. Has a refractive index for visible light of 1.5 or above (higher is better)
  6. Is cheap, or at least not too expensive
  7. Is resistant to chipping or snapping

Can anyone help?

Partial matches to the above might be welcomed, but it would be useful to know why they are only partial matches. The key points are (1), (2), (3), (4) - other than those, the higher refractive index the better, the cheaper the better, the more resistant to chipping and snapping the better, but those are continuums rather than fixed points! The method of shaping also matters, ie something that can theoretically be shaped but in practice requires a really expensive or rare process, or hand shaping, is not practical.

For example, I have access to injection molded Polyester resin, but I understand that might not be flexible.

  • $\begingroup$ Transparent ABS? $\endgroup$ Nov 30, 2019 at 9:17
  • $\begingroup$ unicgroup.com/_en/02_product/03_product_detail.php?mid=27 says ABS has 'excellent [...] strength' which suggests to me no flexibility - am I wrong? $\endgroup$ Nov 30, 2019 at 9:39
  • $\begingroup$ Strength is not the same as stiffness. High stiffness means won't deflect very far for a given force, which is what you are thinking of. High strength means can take a high force without failing. For a given stiffness this means it will bend further before snapping, so high strength is good for you. $\endgroup$ Nov 30, 2019 at 12:23
  • $\begingroup$ Thanks, as a side note you've pointed out something I need to clarify in the question. I'm looking for 'flexible without too much force required' - like a plastic ruler or perhaps a little harder to bend than that. (And yes, I do know the difference between 'strength' and 'stiffness', which is why I asked the follow up question, because I couldn't find anything about its stiffness - so is Transparent ABS potentially bendable as long as I have a handy set of tools, or is it something I could do by hand?). $\endgroup$ Nov 30, 2019 at 16:29
  • $\begingroup$ There are optically clear silicones which are usually used for encapsulation. Don't know how they work in very thick sections, but they may be a solution. smooth-on.com/product-line/solaris $\endgroup$
    – Eric S
    Nov 30, 2019 at 16:48

1 Answer 1


There are optically clear silicone products often used for encapsulation. These are usually two part mixtures that are then cast. They are quite flexible. I doubt they are machinable so you would have to cast to shape using a form or mold of some kind. Here is an example, but there are many others. Just do a Google search.

I've also found optically clear urethanes. Here is an example. Urethanes can be found with a range of stiffnesses.

  • $\begingroup$ Thanks Eric, that's perfect, I've been looking at the suggestions you gave, both very interesting. The Urethane seems particularly good and I'm looking into their refractive index. Again, many thanks, you get the win... $\endgroup$ Dec 2, 2019 at 6:02

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