dried out probe!

[christyf5]

I found this information:

The glass pH sensing membrane may also require service in some applications. This membrane can become dehydrated or coated with a thin layer of deposits. The best procedure for cleaning or rehydrating the glass is to soak the probe in a pH buffer of 4.0 for several hours. If this does not work then immersing the probe in hot buffer 4.0 solution will usually work.

taken from http://www.phadjustment.com/pH_Probe_Service.htm

I don't know how far you can push that "dehydrated" part

Personally I always thought once they get dry (ie. more then a couple minutes out of liquid, they were dead.

Christy