We do everything by the book and normally aim for about 2.4 volumes of CO2 i.e., use the pressure and time Brewfather sugests at our cold crash temperature. We also push our filler to the max and use no more than about 50 cm of 3/16″ tubing as reduction and fill our cans almost to the brim. Still there is not always enough foam to do a proper “cap-on-foam”. We do think the carbonation is ok and blame the lack of foam on to low pressure (15-17 psi) or to low temperature (3C). We do not want to up the pressure or temperature too much, the majority of the fillings actually has an ok foam crown for “cap on foam”.
To save the ones that don’t have a good enough foam crown we designed a “foam booster” out of a cheap ultrasonic washer.
As many of you all know ultrasound is used for degassing of carbonated fluids and if we puls ultrasound into beer for a sub second the beer will start to foam, just enough for a (perfect) cap on foam.
We bypassed the electronics on our washer (buttons, timer, display and so on) and made it “dumb” with a single momentary button for on/off. This way we can control the time the ultrasound is on with our finger tip.
