Why over carbing with small amounts of dextrose??

Hello,

I'm a relatively experienced brewer now and my beers are tasting great, but I'm still having difficulty getting the proper level of carbonation in my beers. I'm bottling my 15th batch today and up until this point, every batch has been over carbonated. Each batch I have been gradually decreasing the amount of priming sugar but the over carbonation persists (over carbonated in the sense that when I pour the beer in the glass the glass fills with about 1/8 beer and 7/8 foam).

My last three beers were a belgian (1.048), an IPA (1.070), and a Kolsch (1.050). Each beer was fermented between 60-65 F, and left in a secondary fermentor around 70 F. Each batch I have dropped the desired CO2 volumes from 2.0 to 1.8 to 1.6, yet the over carbonation persists.

Does anyone know why my beers are still being over carbonated, even when the amount of priming sugar added should only be adding 1.6 volumes of CO2 (which is relatively low for most beer styles)?

Equipment and process: I use a standard bottling bucket at room temperature (70 F). I mix 1/2 cup of water with my priming sugar and boil, then cool before adding to the bottling bucket and stir well while being mindful to mix as little Oxygen in as possible. I'm using brewers friend to calculate the amount of priming sugar to add at 65 F (this should account for the residual CO2 in the beer from fermentation). After bottling, i store the beer at room temperature for 3-4 weeks before opening and refrigerate the beer before opening.

My desire is to be able to consistently carbonate my beers. Its weird that the brewers friend software seems so far off from the predicted carbonation levels. Is there anything I can do moving forward to more accurately and consistently carbonate my beers?

Your help is much appreciated. Thanks

 

I weight out .8 ounces per gallon

 

For my last batch of Kolsch, I added 1.9 oz by weight for 4.8 gallons bottles and it was still substantially over carbonated. This seems like a very small amount of dextrose to get an over carbed beer, right? Is there any thing that can explain this?

 

I assume you've eliminated the possibility of incomplete fermentation?

 

Yes, I have eliminate the possibility of incomplete fermentation. Each beers final gravity is around 1.010 and I typically let them go in the primary for 2 weeks and secondary for 2-4 weeks.

Also, my scale has been calibrated and is seems accurate.