My 35+ years of experience in this area says that there are more factors to this than one might think. To start with, on the subject of setting pearls with glue: Is this a design where the pearl will be standing proud or will it be cemented into a recess? How much of a recess? What is the size of the pearl? If it is going to be standing up out of a recess more than half way, then don't do it. It will get knocked, broken loose and fall out at some point.
As far as glue goes--there is glue and then there is glue. . . Many epoxies break down and loose their strength over time. The ones that seem to hold up the longest are the ones with the longest curing times. I've seen fast setting epoxies degrade in a couple of years. When epoxies are new, then it is almost impossible to loosen them with anything but heat. Even "Attack" usually won't do it. I find the cyanoacrylate glues best but most of them are brittle and will break. There is one called "Flexi-Cure" by the company that distributes "Maxi-Cure" and "Insta-Cure" that seems to be less brittle but it's fairly new. These are some of the best of this type--always use a premium glue. Try hobby shops. Grizzly sells it too.
Prongs--more factors: How heavy are they? Thin ones aren't usually strong enough for a ball shaped gem. The gentle curve of the pearl acts as a wedge. They must reach past the center point of the circumference for them to have any holding effect at all and if they are long enough to really do the job they start to hide/overpower the pearl. Also, if the prongs are sturdy enough to do a good job then you will probably scratch the pearl when setting it. Karat golds are harder than pearls. Glue may help (Insta-Cure) but
nothing other than hard solders hold well to gold or silver. Roughen the glued surface--it helps some. How large is the pearl? The larger it is, the less well prongs or glue will hold it. (leverage)
The best ways are post and glue and fully drilled pearls with a wire runnng through to secure it. (Not good for many designs.) Avoid
cast pearl posts like the plague.
They usually have a crystalline structure and are subject to breakage. Silver is rather weak compared to gold and should have a thicker prong. (...and a wider hole.)
Smooth prongs just don't cut it!! Use a file or jewelers sawblade to roughen the prong. You must have a physical bond--don't count on a molecular bond with precious metals. Again--use a cyanoacrylate glue. With epoxy, for about the first six months or so don't count on unbonding it with anything but heat. (How brave are you?
) After a couple of years or so, many epoxies start to deteriorate. Clean out the hole in the pearl first and make sure that you get the glue all the way down in it. Remove with "Attack."
Good luck!
Marc
http://www.flyrodjewelry.com/home.html