Plastic Beakers ⁽⁵⁾

Polypropylene (PP) is the most chemically resistant and cost-effective option, suitable for dilute acids, alkalis, and most aqueous solutions. Polycarbonate (PC) is optically clear but has limited resistance to organic solvents and cannot be autoclaved. Polymethylpentene (TPX) combines near-glass clarity with autoclavability. Always check the chemical compatibility of the plastic before using it with organic solvents or concentrated mineral acids.

As a general rule, choose a beaker roughly twice the volume of the liquid it will hold, to prevent splashing during mixing. The 250 ml beaker covers most school lab tasks, while the 600 ml is the standard general-purpose size for mixing and dilution. Sizes above 2 000 ml are suited to buffer preparation, waste collection, and large-volume reagent rinsing.

Plastic beakers are graduated for approximate measurement only. The moulded lines are not calibrated to Class A or Class B volumetric standards, and the typical accuracy is within plus or minus 5 to 10% of the marked volume. If your procedure requires better accuracy than that, use a calibrated plastic measuring cylinder or a volumetric flask instead of a beaker.

Polypropylene beakers are autoclavable and can be reused many times with correct washing, making them the cost-effective choice for regular lab work. Disposable plastic beakers are more appropriate for single-use diagnostic or field applications where washing facilities are not available. For school labs, reusable PP beakers are the practical and environmentally responsible choice.

Polypropylene beakers can withstand temperatures up to approximately 121°C and are suitable for low-temperature hot plate use. They should never be placed directly over an open flame or on a high-heat surface, as PP will soften and deform above its heat limit. For any heating application above 100°C, use a borosilicate glass beaker. TPX beakers are slightly more heat resistant and can be autoclaved, but they are not rated for open-flame use either.

Polypropylene (PP) beakers are translucent white, highly chemically resistant, autoclavable, and the most common type in South African school and university labs. Polycarbonate (PC) beakers are optically clear and allow visual monitoring of the contents, but they have limited resistance to organic solvents and strong acids, and cannot be autoclaved. Choose PP for chemical resistance and durability; choose PC when visual inspection of the liquid is a priority and chemical exposure is mild.

Plastic beaker graduations are approximate, typically within plus or minus 5 to 10% of the marked volume. They are not calibrated volumetric instruments and are not suitable for preparing standard solutions, volumetric analysis, or any procedure that requires accurate volume measurement. For those tasks, use a calibrated plastic measuring cylinder (Class B, approximately plus or minus 1%) or a borosilicate glass volumetric flask.

Polypropylene beakers are resistant to most dilute mineral acids (hydrochloric, sulphuric, nitric) and alkalis at room temperature. Concentrated sulphuric acid and concentrated nitric acid can attack PP over time and should be handled in borosilicate glass. Hydrofluoric acid, which etches glass, can safely be used in PP containers. Always consult a chemical compatibility chart for the specific concentration and temperature before using any plastic container with aggressive chemicals.

Polypropylene beakers can be autoclaved at 121°C for standard steam sterilisation cycles and are the preferred option wherever reusable sterile containers are needed. Polycarbonate beakers should not be autoclaved as the heat and steam will cause clouding, warping, and structural weakening. After repeated autoclaving, inspect PP beakers for brittleness or discolouration, which indicate material degradation and that the beaker should be replaced.