Filled my first CO2 tank and...

I learned you should bring gloves! That cylinder was so cold it almost hurt carrying it! I didn't even think of that before I grabbed it from the guy at the gas store. Next time I'm definitely bringing something to wrap it in at least!

How big a tank? I've never noticed that with my 5 lb tanks. But I usually leave them for pickup, so the outside must have time to adjust to ambient temp.

Hmm, mine is usually not cold at all, and they hand it to me immediately. Except for once. My guess is if they overfill it, and need to let some out, it gets very cold, since the liquid co2 boiling off is an endothermic process.

PV=nRT

When, the likely vent some off after they fill it. Tanks get cold if you let the gas too fast, like if your burner is drawing propane fast and the tank freezes...

The place i used to get mine filled at before i moved, always cooled the tank down with dry ice before filling. Not really sure why.

I believe you can get them full more easily by cooling them first. Sometimes they do that by filling them just a little and releasing the CO2 to rapidly chill the tank prior to the actual fill.

CO2 is filled from a bulk tank with a siphon tube drawing liquid. Once some of that liquid enters your tank it expands into a gas and the pressure increases. The two tanks will quickly equalize and no more CO2 will flow from the bulk. In order to keep the pressure in the customer tank lower than the bulk tank it must be chilled. Some shops will put them into a freezer before filling, others will partially fill the tank and then vent it to chill the tank.