[EHall]

A microbrewery here in Northern AZ recently started canning and I was able to get some down here in PHX. All the cans so far I have opened have had no 'pfft' and extremely low carbonation. They taste fine but not much carb. When they were bottling years ago it was all good. I emailed them to ask if they knew there was an issue or they were changing it to be more like a 'cask style'. Here's the brewmaster's response:

You are correct, the carbonation level has been lower in the can than in bottle.  We have been wrestling with just the right level.  Some of the cans remain in Northern AZ and some go south.  If the levels of saturated CO2 are perfect here (2.5v), then due to the change of atm pressure, the beer seems under-carbonated in the valley.  If perfect at low elevation then it gushes up here.  I am trying to nail down a happy medium.  You should expect higher levels in the future.  Thanks for your support!

This doesn't make sense to me. If you carb your beer to a certain level why would it change in a sealed can when taken to lower/higher elevations? I've never come across any other can of beer like this before. I gotta wonder if I'm getting a straight answer...

[rabid_dingo]

Could it be because the cans are less rigid and respond more to atmospheric pressure?
Drop in elevation and the volume inside the can drops(increase in pressure squeezing the sides)?
It may be marginal but it is possible.

The only insight I have is driving from Denver up the mountains to snowboard. We take bags
of chips and sometimes some of them pop. And let me tell you it is loud! I am sure a can
wouldn't pop but the pressure would change with elevation and carbonation could change as well...

[morticaixavier]

The pressure inside the can does not change. the differential between the can and outside changes resulting in CO2 coming out of solution faster. Just as water boils at a lower temp the higher in elevation you get. Don't know why it wouldn't happen to bottles though.

[rabid_dingo]

The pressure inside the can does not change. the differential between the can and outside changes resulting in CO2 coming out of solution faster. Just as water boils at a lower temp the higher in elevation you get. Don't know why it wouldn't happen to bottles though.

Makes sense to me, as far as the differential. But I question the rigidity of the cans. I know that they can
expand and contract a bit hense the change in volume... On the extreme, ever accidentally frozen
a can of soda? It rounds out the ends just before it 'splodes!

[euge]

The pressure inside the can does not change. the differential between the can and outside changes resulting in CO2 coming out of solution faster. Just as water boils at a lower temp the higher in elevation you get. Don't know why it wouldn't happen to bottles though.

Makes sense to me, as far as the differential. But I question the rigidity of the cans. I know that they can
expand and contract a bit hense the change in volume... On the extreme, ever accidentally frozen
a can of soda? It rounds out the ends just before it 'splodes!

I've never had one explode in the freezer but left an unopened can in the car console at the height of summer once. Once.

[a10t2]

The elevation change definitely plays a role, but it isn't going to be night and day. I've opened some of our cans (packaged at 9300 ft) at sea level and the carbonation is only a little low. Theoretically, that should be a difference of about 0.3 vol.

How big a micro are they? If they're filling by hand (on a Cask system, most likely) they may not be getting uniform fills. You really have to baby-sit the manual fillers. If you can, check a full can by weight. It should be 374 g. Anything under about 360 g and you're going to see a noticeable change in carb levels, IME.

[morticaixavier]

...left an unopened can in the car console at the height of summer once. Once.

"You shouldn't hang me on a hook Johnny, My mother hung me on a hook once... Once!"

[bfogt]

"You shouldn't hang me on a hook Johnny, My mother hung me on a hook once... Once!"

Just what I was thinking.

I wonder when contests will let us send in cans! 

There was a whole canning line in a storage shed around these parts a while back.  21A bought it but found a better one or one that fit their space better.  They have community canning facilities for pickles and beans.  Why not one for beer?

Back to the pressure problem.  An industrious person would volunteer for the job of traveling to EVERY market served by a brewery to try each of their products to make sure that it was properly carbonated in that location.  I mean, Quality is Quality.  All expenses paid, of course!

[maxieboy]

Back to the pressure problem.  An industrious person would volunteer for the job of traveling to EVERY market served by a brewery to try each of their products to make sure that it was properly carbonated in that location.  I mean, Quality is Quality.  All expenses paid, of course!

If this is an offer, I'm volunteering! 

[EHall]

I weighed the cans, my scale that is in grams doesn't go that high so its in ounces.
can1 12.5oz
can2 13.3oz
can3 13.1oz

So definately different fills... I guess the extra headspace could contribute to a change... just didn't think it would be that signifigant. I'll email him back but I"m willing to bet he has an older canning machine...

[tschmidlin]

Did you taste cans 1 and 2 side by side and see if there was a noticeable difference in carbonation level?

[beersk]

...left an unopened can in the car console at the height of summer once. Once.

"You shouldn't hang me on a hook Johnny, My mother hung me on a hook once... Once!"

Awesome!  I immediately thought of Danny Vermin also!
"You shouldn't kick me in the balls.  My sister kicked me in the balls once.  Once!"

This is just weird.  I've never even thought about the possibility of differentiating carbonation levels at different altitudes. 

[EHall]

I did open them together, could visably see a different level in them and the fuller one had slightly more carb but still under carb'd.