I knew from gluing panels together with Gorilla Glue that it foams up and cures very hard. So I wanted to see just how much I could get it to foam up so it would fill gaps where the panels meet. I mixed about a teaspoon full with 3 drops water in the plastic jello cup. After 15 minutes, it had expanded to what you see in the picture. It still cured very firm, much harder than Great Stuff. So when I glue up all the top panels, I'll mix some water in with the glue so it will fully expand and fill any gaps. It pays to test!