This is my first tutorial, so bear with me, while wary of cringe.
EDIT: Apparently (to no surprise, considering the 5+ years Glass existed) someone already found this, and it puts it in a more to-the-point format of making it:
Hey there! If you’re here you probably liked my post about a strange property of glass! Well, I’m here to elaborate on that, and provide some limits I have found while trying to use it.
HERE-A WE GOOO!
FIRST: Create a Glass-Material part… duh.
NOTES: Make sure is it not a square… That way, the effect is more noticeable. Try a Sphere or Cylinder! I’m doing a Cylinder.
Make your Part:
SECOND: Raise the transparency!
NOTES: Make it more than 1 if you want this effect… otherwise, why did you come here…?
I’ll do 5! Make sure to keep selected on the Part. If you don’t, it will disappear from sight. If you do end up deselecting it, just select it in the explorer, if you can’t find it, or in the Viewport, if you can find it.
Selected:
Deselected:
This is because transparency is >1! “Then, why make this, if it’s just gonna disappear upon play?” you might ask. And the answer is, I have a way around this… STEP THREE!
THIRD: Add a Highlight Object!
NOTES: This part is… finicky… And, overall, I don’t know how this works! I just know that it does (can someone explain, if they find out? that’d be great 
)!
What you need to do (unless you want this distortion to be colored) is make both Transparency values (both Fill and Outline) 1. This means that this Highlight is blank, and actually doesn’t do anything! Now if you deselect the Part, it won’t disappear! Hooray!
Make the Highlight:
Properties:
Deselected:
CONGRATS, YOU MADE A DISTORTION EFFECT!!!
But, as I said, there are technical limitations… So, I’ll try my best to list all I have found, here…
TL;DR buggy, but usable
The first, I should mention, is that (obviously) it won’t show anything that regular transparent glass wouldn’t show. “Ok, small price to pay, for better distortion…” Not quite…
This is just a bug with Highlights in general… If you have other highlights, this will get very buggy in Studio mode! Colors of other Highlights in your games will swap, despite even the Adornee option set to the right Parent!
In my testing place, I have a Dark Sonic with some Highlights on it… Look here:
His glove should be dark with the Highlight! but it’s color swapped with the Glass Part’s Highlight. And, as you can see, the Adornee of the empty one is set to the effect part we made! It’s annoying, but you’ll get used to it, as this is only a bug within Studio/Editing mode. It will not carry over to Run/Play mode, AFAIK from testing.
Another thing to note, is that in 3D Particle Emitters, it just decides to stop… Don’t know if that has to do with the thirty-something Highlight limit, but I’m too lazy to check 
As this is a “glitch” this may get patched in the near/not-so-near future! If it is, I hope by that point we’d have support for some kind of Distortion Maps, lol.
If you are going to use this, keep in mind that the 8-below Graphics Settings don’t support Glass Distortion, so this will go bye-bye for those players… Also, I’d use it places like, stationary torches or fireplaces, where the distortion is also stationary.
One more note, changing the Transparency of the Part even higher will cause it to have more of a kick with it’s effect. I find 10 good for most cases, even tho I did 5 here.
Thank you for reading (and, hopefully, putting this to use)! I hope to make more of these in the future (maybe not, lol), and look forward to hearing on how you possibly could improve this (maybe a less buggy workaround than the Highlight)! I’ve been thinking on creating a series of posts recreating some famous game engine (Ori and the BF/WotW? Metroid? Overwatch?), pushing the Roblox Engine to it’s limits, recreating a game that people love (Of course, I won’t publish it to Roblox for fear of Copyright)! Tell me what you think about that idea, might make it a reality…
Anyways,
LATER, DEVS!