red cabbage makes a tolerable indicator:
http://www.cchem.berkeley.edu/demola.../CabbIndic.htm
You can make your own pH meter but I bet its costly and a pain to calibrate. I think some saltwater aquarium users have them, and you can probably get litmus paper at the pet store too.
the pKa of ethylene glycol is 14.22, so it is basically completely present as C2H4(OH)2
(my weird notation to show that the OH on the alcohol groups are present and not O-)
Can just calculate pH using henderson-hasselbalch eqn:
pH = pKa + log (A-/HA )
oops too many unknowns; better just measure
