I've had two attempts at making my own salt water hardened eggs sacks. Last year I used chum eggs from a nice doe I caught. I scraped the eggs off the skien with a spoon (they won't break) then hardened them in a saturated salt brine. They looekd awesome when done, but popped pretty easily if you squeezed them. I tied up a butt load of sacks with them and (foolishly!) froze them (didn't know better). Well, most of them burst! Of the ones that didn't burst, they were not that durable and broke easily when fishing them.
After that learned online (a lot on this site) that you want MATURE eggs, pretty much from a fish that is ready to spawn. Apparently the eggs are much fuller and the membrane is much tougher.
This year/try #2. I kept some chum for smoking, but none had eggs that were that mature. So I just bought some single chum eggs from Fred's. Not terribly cheap but you can tell they are NICE mature eggs. They were pretty durable the way they were, but I wanted them extra tough, so I did up a saturated salt brine and left them in there overnight. The result was a super plum and tough egg. I'd have to squeeze one very hard to get it to pop. I tied some smaller sacks for clear water or to put on the back of a jig, and some bigger sacks for fishing ona bare hook. I've stored them in the FRIDGE this time, out of the salt sollution, just in mason jars. I'm sure they would keep longer in salt water but I plan to use them up over the winter.