On Thu, Mar 18, 2010 at 10:17 PM, Russell McMahon wrote: > It seems that pumping it up with CO2 may be useful :-). There are services in some places in the US that do "easy at-home soda making" which consist of the syrup, a bottle, a cap with a fitting, tube, and regulator going to a CO2 canister. Add water and syrup to the bottle, screw on cap, pressurize with CO2 (90 PSI IIRC), and shake until the CO stops hissing into the bottle (as the beverage absorbs it, the presure decreases allowing more CO2 into the bottle, so there's a disitinctive hissing as it carbonates). You don't have to shake, but then you've got to wait overnight for carbonation to happen. Very quick and easy, and a lot more carbonated (if you want it to be) than what you get from the store pre-bottled. A lot of people around here use dry ice (frozen CO2) to create rootbeer. Water, extract, sugar, and a block of dry ice, and you've got fresh, ice cold rootbeer. Food grade dry ice is available from a few local grocers, in fact. I imagine if someone invented a bottle cap that integrated a little CO2 cartridge (perhaps the small ones used for pellet guns) it'd work very well at keeping the drink fizzy. But pressurizing it with room air isn't going to help that much, unless you're looking for dissolved nitrogren rather than dissolved CO2... -Adam -- http://chiphacker.com/ - EE Q&A site -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist