I put a circle of GE II where the 2 items touch, not all over the whole area - Laura

you want to put an abundance of the silicone a thick bead, press pieces together, you want the silicone to ooze out all the way around assuring a full seal. Then dip your finger into water and run it around the edge where it is oozing out, keep wetting your finger as you work your way around. I keep paper towels handy to wipe up the excess from my finger. Do that all of the way around every seal you make. It locks the seal tight and should create a water tight seal.
If you don't do that and have weak or lacking spots in the seal it will allow water to seep in and will create water vapor in the sealed pieces if it is a container type piece like those used in totems.

Using things that are not flat edges will be more difficult but using plenty of silicone on these is essential for that reason.
I would guess in the absolute perfect conditions crystal glassware in the sun could act like a magnifier and start a fire. Haven't heard of this happening.

Thanks for the response. I have been trying to finish up a few projects before tackling this one. I have gotten almost 7 projects done this week, Yeah!! I need to quit seeing things I want to do.

It is the curse of my life to see something I want to do, gather up a big portion of the things needed and then set it down to finish something else and get back to it a year later. All the while getting this and that to complete what ever it is but not getting it done immediately.

Do any of the rest of you all suffer from delayed completion? I do get done eventually, much to the surprise of my DH.