Are the liquid type Ph test kits accurate?
Liquid Ph test kits offer the grower an inexpensive alternative to the expensive test meters and give results which are accurate enough to accomplish the task just fine. Usually reading within +/- two tenths of a point (.02) of electronic meters, depending on the kit.
For the grower looking for the most accurate Ph control, there are many various electronic Ph testers available that when calibrated will give extremely accurate readings. Unfortunately for quality units, you may be looking at a higher price than you are able to pay, even the best units will suffer down time as probes go bad. Ph probes are especially prone to failure as the membrane ages, eventually drying out and failing.
The most common solution to fill the void is liquid type Ph test kit.
They're quick, reasonably accurate and very inexpensive.
Great backup in case your probe fails.
When using liquid Ph testers, there are some important things to keep in mind:
Always use a white background when looking at the color in the vial.
A non white back ground can alter the color subtly enough that you may end up being off by anywhere from a little to a lot depending on the color background being used.
Make sure that all color comparisons are done under natural light or normal household lighting and NOT HID light, as the red/blue spectrums of the light (HPS and MH respectively) will cause serious variations to the appearance of the solution, and in some cases you could be running your solution as much as a whole point above or below what it should be.