Resin? acid free varnish

I am a beginner and I have made several different size bezels that I
would like to place collage and found object type things and encase
them in a sort of resin? I am not sure if that is the right word, but
I am also using old metal pill boxes that I am turning into pendants
etc and I want to pour some sort of solution into them that will
harden and encase the objects in a clear type varnish. Does anyone
have any sources and instructions on how to do this? Any info would
be great!!

Nikki in Dallas