Jewelling is not some magical thing that makes paint looks amazingly better. It is really a term that I started using because I heard others use it as well to describe taking the paint to a higher level, even when it already looks close to perfect. This is has been done forever by porter cable users.
You can make paint defect free by using a medium polish and pad and make it look good. Most of the time using a finer polishing pad and finer polish will result in more glow or sharpness from the paint.
When you using a rotary it is possible to remove all the holograms and paint defects and still likely have microscopic defects on the paint's surface. Any defect that cannot be seen still scatters (or refracts) small amounts of light which can take away from the overall finish. To work out these microscopic defects you should use a pad with little to know abrasive (mechanical) property and a very fine abrasive that will finish down with no cutting power. Then slowly massage out these hidden defects which will end with the surface of the paint being more microscopically flat and true.
If the surface is milled like a diamond and flat it will reflect (instead of refract) more light which will increase the over all optics of the paint. As Ryan Blanchette (a friend and amazing paint polisher)/rydawg has said to me, "hell I'm just getting started when the paint looks perfect."
Also, since pads can and will abrade the clear coat’s surface and allow the carriers of the polish (most commonly mineral oil) to leech into the small abrasions, you can sometimes a light shadowing of holograms return up to several months later. The final jewelling step (or in some cases: steps) can eliminate the pad abrasions and prevent any defect return.
When we put 30 hours into a paint job, the paint has been perfect for 25. The last 5 hours are focused (thru trial and error) of finding the best combination of product, pad, and technique that will give us mind blowing results and make our haters think we are doctoring our photos (which is always nice when a client pops on here and comments the pictures do not do the car justice). Or when our cars win best paint at major shows, etc... It’s in the microscopic polishing and chasing 1%'s that makes all the difference, IMO.
Using a pad with the no mechanical ability (though harder paints can "tolerate" slight mechanical action such as a white LC pad on a Corvette for example) and an ultra fine polish and massaging the paint will moderate to lower RPMS (although you will want to use a little pressure at the beginning of the pass to help fracture the abrasives since the pad isn't providing abrasion) and backing the RPM to match the fracture rate of the abrasive of to ensure it is smoothly polishing it self out is my definition of jewelling. Experience and a keen eye to match the best finish to each paint is also necessary for best results, though you cannot start learning what works for you until you start trying.
Now keep in mind that on a professional level this will not make sense because a lot of clients are not willing to pay the money for the considerable amount of time required to jewel the paint perfectly. There are no set rules because each vehicle's paint is different (even same year/make/model) and we detail in dynamic environments. However once you have the paint perfect, dare to make it better. Never settle and you might be surprised!
Here is a video in which I explain what I feel are the merits of "jewelling" a finish and a small demonstration on a Ferrari.
Please ignore the stuttering in the video
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direct link
YouTube - Bella Macchina-Proper Paint Jeweling