I've never heard of index matching fluids! Will have to read up on this.

Video on the project https://vimeo.com/354927033

I actually discovered pretty early on that my interest was more in clocks than watches, but the early explorations in the watch realm were almost entirely applicable to clock repair as well. I have since repaired at least a hundred clocks and pocket watches. Next month I'm going down to the NAWCC school of horology in Columbia, PA to take my third workshop there, this one on the repair of wooden works clocks. The school was closed for a number of years, but has fired back up in the past few and I know they're actively working on getting more watch repair workshops going. Last time I was there they were just putting together a killer watch lab with some very expensive benches and equipment.

You will need a set of flat headed screwdrivers. These are 80% of the tools you'll be using.

If you are approaching middle age, you'll need some magnification. I dont like loupes (those lenses you hold to the eye), and the visor mounted magnifiers are also not that good for me. I got a second hand long armed stereo 10x microscope for £30 which is perfect for me. You might just want a big old magnifying glass.

You might want a movement holder, again you can get super cheap ones, but second hand ones are better (because the shit ones are thrown away). they are basically specialized vices, or tiny little buckets(those are custom to each movement though.)

Next, start off with pocket watches, they are much bigger and more forgiving, and also cheaper.

In the uk: H samual, Thos russel are good brands to look for anything £20 or less.

For america: waltham/elgin (they often have broken balance though so watch out ) Eglins and Walthams look a lot more pretty, and have a better standard of finishing than the english counterparts.

https://sutcliffehansen.com/pages/tool-kits

I guess the epoxy's index of refraction depends on all kinds of factors such as the mixing ratio and the conditions under which it cures.

The question is whether there is any overlap at all where the price would be high enough to motivate supply (worth it to him) but low enough that there's still demand (worth buying). Also factoring in the cost of marketing, since potential buyers don't just automatically find you.

There are a huge number of business ideas where there is no overlap at all. Finding an overlap even without competition is hard enough. (Then add competition and it gets even harder, of course.)