There are two main risks associated with using kitchen glassware for chemistry experiments. The first centers on the type of glass itself, and whether it is appropriate for the experiment. The second deals with the potential for cross-contamination between food and chemistry uses. As with any science, common sense should not be abandoned.
Types of Glass
Laboratory glassware is a specific type of glass known as borosilicate. Borosilicate glass has excellent thermal properties, allowing it to be heated to higher temperatures than other types of glass that are often found in kitchens, including flint glass and lead glass. Borosilicate glassware has a high melting temperature, and can withstand heating and cooling cycles without breaking. Laboratory glassware is also fashioned without seams, to avoid weak spots that will give way to strain when heated. Some kitchen glassware is also made from borosilicate. Anything bearing the brand name “Pyrex” is borosilicate. (There are other brands as well, but never assume without verifying first.)
Even if you aren’t going to be heating the glassware, borosilicate is the better choice. It is relative inert (strong bases can dissolve it very slowly), and will not contaminate most experiments. Flint glass is softer and typically has more impurities. Lead glass, obviously, contains lead, which may be leached out of the glass. Few things are more frustrating than an experiment that fails or gives unexpected results just because you used the wrong container.
Contamination is a problem in both directions. Chemistry experiments can be ruined by food and detergent residues. Chemical residues can pose a threat to people eating from the dishes later on.
The bigger hazard is certainly the risk that someone will end up eating or drinking the chemicals that were used in your experiment. That might not seem so bad if only vinegar and baking soda were used, but home chemistry could just as easily involve more harmful chemicals like bleach, drain cleaner, rat poison, battery acid, window cleaner, gasoline, mineral spirits, and more. Even small exposures to some of these chemicals can cause symptoms from mild irritation to chemical burns to outright poisoning.
Chemistry experiments are often sensitive to the environment they are in. Detergent residues on glassware may produce unwanted bubbles or a surfactant layer that interferes with a reaction. Food residues may also interfere with experiments, potentially changing pH, providing unintended rough surfaces where crystals may form, or any number of other unexpected effects.
Not every home chemistry experiment uses intense heat or toxic chemicals. You, the experimenter, need to take into account the requirements and risks involved with the specific experiment when deciding if kitchen glassware is acceptable for use. You might evaluate using guiding questions like these:
1. Do I have to heat the glass directly?
If you will be heating the glass over a burner or on a hotplate, borosilicate should be your only choice. Cheaper glass should be okay in the microwave, or in a pan of boiling water, where extreme temperatures are not reached. An old pasta sauce jar is perfectly fine if you’ll be pouring hot liquid into it for growing crystals. It would be a bad choice to place above a burner, where it can easily melt or shatter.
2. Are any of these chemicals toxic?
If any of the chemicals are toxic, you should assume that any glassware (or utensils) that you use in the experiment are forever contaminated, and never to be used for eating again. If you’re just making sugar crystals, vinegar and baking soda volcanoes, or other food chemistry type projects, then there should be no problem with using your regular kitchen glasware.
3. Am I using harsh chemicals that can leach chemicals from cheap glass?
If you’ll be using strong acids or bases, use borosilicate. (Drain cleaner and battery acid are examples of harsh chemicals.) Do not use this glassware for food ever again. Also wear protective equipment for your eyes and skin!
4. Am I doing something that would be sensitive to food or detergent residue?
Most introductory experiments at home aren’t likely to have this problem. In most cases, residues would just lead to cloudiness. Checking for cleanliness will be good enough for most applications. If you are doing something more sensitive however, either use real borosilicate lab glass, or consider thoroughly acid-washing the glassware you plan to use. (And if you have hard water, remember to use bottled distilled water to rinse, not tap water.)
5. Am I working in the kitchen?
A standard rule of lab safety is that you should never eat or drink in the lab. Make this the rule at home too. If you are doing an experiment in the kitchen, no one eats or drinks until the experiment is cleaned up and all the glassware is accounted for. That way no one accidentally eats or drinks any chemicals, and no one calls poison control. If the experiment is going to be a long one, cordon off a specific working area. Keep food and drinks away from the working area, and keep all chemicals and glassware inside the working area at all times. Don’t be flexible, and don’t be careless.
Get Your Glassware
At the end of the day, if you enjoy doing chemistry at home regularly, you’re best off investing in your own laboratory glassware. It doesn’t have to be a large expense either. A cheap (but still reasonable quality) source of glassware is Science & Surplus. Scientific, while not always cheap, also carries a selection of glassware for the home scientist. For more specialized glassware, you can try VWR, a worldwide company that supplies schools and industry alike.