Liberty ImportsPack of 12 Wedding Style Stick Umbrellas Large Canopy Windproof Auto Open J Hook Handle in Bulk Photo Props

Q: What material are the white ones made of?

I don't know about the white ones but the clear umbrellas were made out of see through plastic with white handles, and were well made and looked nice.

Q: Would these also provide adequate sun blocking for an outside ceremony, on a hot sunny day?

I don't think so. The ones we got were clear plastic - it seems like the sun would just beam down through them and maybe even magnify the sun onto the person. There was another type that was pure white made out of regular umbrella fabric....those would probably work. The size was definitely able to be used by two people. So if your seats were close together, two people could block most of the sun with the ALL WHITE ones vs. the ones we got, which again, were clear.