A real question about ultrasounds

As we watched "Juno" a few weeks back (fifth time) I paused the movie at one particular scene. The scene where Juno McGuff is getting her ultrasound. The ultrasound technician squeezes the bottle of ultrasound jelly on Juno's pregnant belly and the bottle sounds rather obviously less than full. It sounds like a sputtering plastic ketchup botttle as it reluctantly gives up some of its last ketchup.

My question is about those ultrasound jelly bottles. Do they come from the ultrasound jelly plant only half full? I remember when my old lady got her ultrasound just like Juno's and that bottle sputtered like a backfiring engine when it was squeezed. And the one at Rochester's Mayo Clinic did the same thing. So, I jumped to the conclusion that there's some sinister company somewhere in the country churning out less-than half-full bottles of ultrasound jelly.

But is there any truth in my assumption? Has anyone actually seen a full(ish) bottle of ultrasound jelly that didn't spit and sputter that cold (from what I've heard) goo all over their pregnant belly?

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