Swing tops didn't carb!?

[AlexM40]

I bought a case of 16 ounce swing tops at my local brew supply store. Being new, I rinsed them with hot water and then sanitized them with Star San on brew day.
I bottled some in 12 ounce bottles and the majority in my new 16 ounce swing tops.
The batch in the 12 ounce bottles are nicely carbed and have a good head while the swing top batch are flat, or almost flat.
Do new bottles have to be washed with cleaner? Do they have a coating that could impede carbonation?
It's strange, I hate to pour 19 bottles down the drain.

 

[Dixon9717]

I've used swing tops a lot and never noticed a difference from crown caps. Maybe your seal wasn't seated properly?

 

[AlexM40]

I checked the seal when closing and they seem to squeeze down tightly. I was thinking that I didn't properly wash the brand new bottles. I assumed that because they're new all I needed to do was rinse them, then Star-San them and bottle. Could they have been coated with something from the factory?