Air Buoy Akin to water keeping something afloat, samples can be"lifted by air, artificially decreasing their apparent weight. This air buoy- ancy can have a significant effect on smaller samples. Electrostatic forces Electrostatic charges are almost always present in any enviro ment, particularly in areas with very low humidity. If there are considerable charges present in a sample to be weighed on a high precision instrument, it will manifest itself in the form of drifting constant increase or decrease of weight readings, or nonrepro- ducible results. Variability occurs when these electrical forces build up on the sample and the fixed parts of the balance that are not connected to the weighing pan Substances with low electrical conductivity (e. g, glass, plastics, filter materials, and certain powders and liquids) lose these charges slowly, prolonging the drift during weighing. The charges most likely originate when the sample is being transported or processed. Examples include friction with air in a convection oven, friction between filters and the surface they contact, internal friction between powders and liquids during transportation, and direct transfer of charged particles by persons. This charge accumulation is best prevented by use of a Faraday cage, which entails shielding a space in metallic walls. This frees the inside area from electrostatic fields. a metallic item can serve the same purpose. Surrounding the container that houses the reagent in foil can also reduce charge accumulation. For nonhy groscopic samples, adding water to increase the humidity inside the draft chamber can reduce static electricity. accomplish this by placing a beaker with as much water as possible into the draft chamber. An alternative is to bombard the sample with ions of the opposite charge, as generated by expensive ionizing blowers and polonium radiators. A simple and effective solution is to place an inverted beaker onto the weigh pan, and then place the sample to be weighed onto the inverted beaker. This strategy increases the distance between the sample and the weigh pan, thus weakening any charge effects. Tempere Airing out a laboratory or turning the heat on for the first time with the change of seasons has a profound effect on an analytical balance. The components of a weighing system are of different size and material composition, and adapt to temperature changes at Troutman et alAir Buoyancy Akin to water keeping something afloat, samples can be “lifted” by air, artificially decreasing their apparent weight. This air buoy￾ancy can have a significant effect on smaller samples. Electrostatic Forces Electrostatic charges are almost always present in any environ￾ment, particularly in areas with very low humidity. If there are considerable charges present in a sample to be weighed on a high￾precision instrument, it will manifest itself in the form of drifting, constant increase or decrease of weight readings, or nonrepro￾ducible results. Variability occurs when these electrical forces build up on the sample and the fixed parts of the balance that are not connected to the weighing pan. Substances with low electrical conductivity (e.g., glass, plastics, filter materials, and certain powders and liquids) lose these charges slowly, prolonging the drift during weighing. The charges most likely originate when the sample is being transported or processed. Examples include friction with air in a convection oven, friction between filters and the surface they contact, internal friction between powders and liquids during transportation, and direct transfer of charged particles by persons. This charge accumulation is best prevented by use of a Faraday cage, which entails shielding a space in metallic walls. This frees the inside area from electrostatic fields. A metallic item can serve the same purpose. Surrounding the container that houses the reagent in foil can also reduce charge accumulation. For nonhy￾groscopic samples, adding water to increase the humidity inside the draft chamber can reduce static electricity. Accomplish this by placing a beaker with as much water as possible into the draft chamber.An alternative is to bombard the sample with ions of the opposite charge, as generated by expensive ionizing blowers and polonium radiators. A simple and effective solution is to place an inverted beaker onto the weigh pan, and then place the sample to be weighed onto the inverted beaker. This strategy increases the distance between the sample and the weigh pan, thus weakening any charge effects. Temperature Airing out a laboratory or turning the heat on for the first time with the change of seasons has a profound effect on an analytical balance.The components of a weighing system are of different size and material composition, and adapt to temperature changes at 52 Troutman et al