David,
Thanks for the reply. What you're saying makes sense except for one thing. In my case I primed one of my beers with 3/4 cup corn sugar and the other with 1 1/4 cup dme. Shouldn't the volume of CO2 produced be the same at sea level as at 9000'? It seems to me that since the bottle is rigid and sealed (ie the volume inside the bottle is constant at sea level and 9000') the amount of CO2 dissolved into the beer would be the same in both cases and altitude wouldn't have any affect.
As I'm writing this response something occured to me that might explain it. Let me know what you think. There is residual CO2 dissolved in the beer from fermentation, before priming, right? This is about 1 atmosphere (give or take), right? Priming with 3/4 cup corn sugar brings the pressure up to about 2.5 atmospheres. Assuming that 1 atmosphere at 9000' is about .5 atmosphere at sea level, my final carbonation (.5 atmospheres at 9000) would be the equivilent of about 2 atmospheres at sea level because the residual carbonation is reduced by 50%. That would mean that my carbonation levels at sea level would be about 80% of what I have at home. Does this seem right? If so I would need to increase my carbonation level up to about 3 atmospheres if I wanted to take some good homebrew to my Dad in Texas?