Giant bubbles!

I tried making giant bubble solution using glycerin, water and dish soap.  It didn't always do what I wanted it to do,  1 out of 8 times were successful with big glorious bubbles...  the other times, not so much. Anyone have a recipe for these that they have actually used and got great results with? I want to do a photoshoot in the park next weekend during the golden hour... if the solution doesn't work well, frustration will show on my subjects faces.