Ph Questions

[llamalord305]

Im doing a science project about pH of water and how it affects plant growth. I my question is; how do I consistently raise or lower pH levels? I have heard about baking soda to raise it, vinegar to lower it, and I heard Pet stores sometimes sell pH lowering and raising kits. (I know they sell pH testing kits, thats what ill get to make sure I have the desired amount.)
Thanks in advance.

 

[celaeno]

this may be useful to you:

http/dataguru.org/misc/aquarium/calKH.asp

 

[Spooky76]

it isnt that simple just to raise / lower your PH, certainly not over a period of time. Depends what your buffer is like in the tank really. Also PH does tend to fall over time. But your on the right lines. That website pretty much explains it.