Test tube holders come in two main types: tongs and racks. Tong types are either wood or metal. They're designed to grasp and transfer test tubes that are too hot or dangerous to safely handle bare-handed. Wood versions resemble clothespins with a long handle. Metal versions resemble kitchen tongs, except they're spring-loaded to hold something securely. Rack type holders serve to store and organize test tubes on the work surface. They may hold a single row of tubes, or a grid of rows.
Convenience and Safety in Performing Experiments
Many science fair projects employ test tubes in various ways. Since a test tube won't stand on its own, a helper is often needed to carry out an experiment. Having a test tube holder allows a single person to perform many experiments. It's also safer for experiments on pressure like popping corks or foaming reactions, where the directions say something like "do not point the tube at your face or anyone else," because a test tube holder will keep tubes pointing straight up. You can even make a xylophone out of water-filled test tubes.
Test Tube Holders as General-purpose Grabbers
Since clamp type holders are spring-loaded to close around items, they're handy in setting up a science fair display booth. Wooden versions can serve as clips to hold things together, or to support hanging items like display boards. Combined with an easel, they can help to improvise a standing flip-page presentation. Metal versions can help you retrieve test items from an immersion bath, or hold them over a flame. They allow a safe distance between the hand and the item being held.
Test Tube Holders Support Classroom Activities
A single-row rack is perfect for holding classroom experiments and demonstrations with plants and cuttings in test tubes. They're good for long-term experiments with side-by-side comparisons like measuring water uptake or the effects of different rooting solution formulas. Another popular experiment is to set up two tubes with different food colorings, and split a white carnation flower stem so one side is in each solution. The rack supports the tubes while the flower absorbs the colors.
Storage Racks Make Good Organizers
A multiple-row rack is good for organizing narrow items like marker pens, pencils, and scissors in a classroom or laboratory. Since test tubes come in a range of sizes, so do the compartments in the racks. Each item has its own compartment, so there's no jumble to sort through. This makes them useful in the classroom for teaching the principles of sorting and organization. They are a stable and portable form of storage, so they can be easily secured when not in use.