Furthermore, the glass ones are easier to clean. Well, yes and no. There are partial immersion and total immersion thermometers, red alcohol-filled thermometers, mercury thermometers, digital thermometers and electronic digital thermometers with a timer and alarm and a switch to allow you to measure the ambient air temperature or the temperature of a solution by switching over to an attached probe. Oh, yes, I forgot to mention that you can get them in Centigrade, Fahrenheit, or both. In dealing with micro-organisms, it is often important to keep a record of temperature to get an indication of the ranges at which some species thrive and others languish.
Many organisms have fairly stringent pH requirements.
A sample taken from a cold lake and then brought into the lab will warm significantly and this can alter the pH. As the culture develops over the hours and days, oxygen will be consumed and there will be an accumulation of waste by-products. Both of these factors will gradually alter the pH, so you may wish to measure the pH and then adjust it to an optimal state by the use of buffers. For example, you can select a paper that will measure from 6.0 to 8.0 in 0.5 increments. The strips or rolls of the paper come with a color chart and after you thoroughly wet a portion of the paper with the solution you are testing, you can match its color with the chart to determine the pH. For many general applications, these papers are perfectly suitable. If you require greater accuracy, then you might wish to consider the purchase of a pH meter.