I recently experimented with a process of germinating old spinach seed where the seed is placed in cold water and held 24 hours in the refrigerator; dried for two days: then back into the refrigerator for up to a week before sowing. I tried this with some Maui pepper seeds as well and it worked. I had some saved sweet pepper seeds which I soaked yesterday but more than half the seeds were floating when I removed the jars from the refrigerator. I know tomato seeds which float are probably not viable, but I don't recall if the same applies to pepper seeds.
I don't think it is something that is that reliable for small seed as a little bit of air adhering to the seed will make it float. I suspect it is even less useful for something like pepper seed because it is somewhat cupped and can easily trap air.
I tried a 24 hour soak with stirring before and after placing the water jar with seeds in the refrig. However, somewhere in the back of my mind I recall pepper seeds which float may still be viable, however I can not find any references in my down loads. My files on peppers and seed saving is rater extensive and it may take a couple of days to completely review them. Just looking for a fast fix incase anyone knew for sure. Memory just isn't wht it use to be.
Pepper seeds... I always soak them (in water with a splash of hydrogen peroxide) to speed germination. A stir or two gets rid of air pockets. The ones that sink almost always germinate... I've had a few floaters germinate, which surprised me, but usually if they still float after, say, 6 hours they're not viable. But, you know, if you don't plant them, then they definitely won't germinate. ;-)
I paid a little more attention this time, and I'm not sure I noticed any difference in germination between floaters & sinkers, although fresher seed (that sank right away) did come up a little sooner, no surprise there.
I've seen on many forums that people use the float test for flowers as well as veggies. But it seems to more of an old wives tale. I had some Roselle seeds soaking and some of the floaters were starting to sprout. Little white nubs were sticking out.
To save pepper seeds, I let peppers ripen on the plants then dry in my shop all winter. I crumble up the dry peppers to get seeds to plant, so I never have them in water to know if they float or not. Same with beans, okra, and such.
I ferment seeds that I'm saving from tomatoes and cukes, though, to get the protective layer off the seeds. At the end of those fermentations in plastic cups, I use a garden hose and rinse the pulp away from the seeds, kind of like panning for gold. The good seeds sink to the bottom and the pulp and immature seeds float or are suspended in the water so they get swirled out of the cup and discarded. With those veggies, anyway, it seems to me that immature seeds float and good, viable seeds sink in water. I don't know if that's true of peppers, though.