Glass test tubes are pretty close to being ubiquitous in a laboratory setting. Usually roughly finger length, these mad scientist staples can be found by the hundreds in situations ranging from chemistry labs to hospitals to a kid’s chemistry set. Any place where it’s necessary to keep samples separate, you’re going to find glass test tubes.

Glass test tubes are also known as beakers, sample tubes and culture tubes, although some people maintain that there is a difference between a culture tube and glass test tubes in the shape of the mouth. Test tubes normally have a rounded lip on them that makes them easier to pour, and this may not be found in culture tubes, although the terms are generally interchangeable.

They tend to be between 10 to 20 mm and between 50 to 200mm, and may have either a flat or rounded bottom. The rounded bottom is more typical, since it discourages people from just setting the test tubes down, which can lead to breakage and accidents. As the name might suggest, most glass test tubes are made of, well, glass, but plastic test tubes aren’t uncommon. One thing that you may need to check on if you’re planning to purchase test tubes is whether the glass is regular glass or borosilicate glass.

Borosilicate glass enables you to use the glass test tubes directly over an open flame. If you try this with regular glass test tubes that aren’t design to withstand heat, you’ve got a better than average chance of the test tubes cracking or even exploding if you get them past a certain fairly low heat threshold.

Glass test tubes are most commonly used by chemists, although they are common through out most science industries. Chemists typically use them for a variety of purposes, including but by no means limited to: holding, mixing and heating liquid or solid chemicals, usually in small amounts.

Most commonly, they are used in qualitative or essaying experiments. Their shape is ideal for minimizing mass loss when pouring, and their narrow shapes helps scientists more easily control the amounts that they are pouring out of the tubes. This shape also slows down the release of gases into the environment, since only a small amount of the surface area of whatever you put in glass test tubes is going to be exposed to the environment.

It’s also fairly easy to use glass test tubes to help capture gases during experiments, particularly electrolysis experiments. Generally speaking this is done by filling the beaker up with water and then up ending it into a larger container also filled with water.

Outside of chemistry, glass test tubes are very common in biological and microbiological laboratories, where they are used to culture and store organisms. Plastic test tubes, which are just discarded after use, are also common in these sorts of labs. Glass test tubes are usually bought in bulk, and it’s pretty common to buy them in groups that also include rubber stoppers and racks to hold them in. Because of their extensive use, they are very easy to find.

When it comes time to buy test tubes are they going to be used just to hold and secure specimens to be placed on a slide and examined under a microscope? Will any of the contents be heated at high temperatures, or promote corrosion within the test tubes? What about an identification system? What colored test tubes be helpful, or too likely shield the contents from view? What about cost? Plastic test tubes are the least expensive, but are there restrictions in their use? 

The majority of test tubes are basically used to hold and secure your specimens for examination under a microscope, or content that are noncorrosive to be mixed with other such content. For such applications the least expensive glass or plastic test tubes are quite adequate. Plastic test tubes are particularly susceptible to corrosion though, and should not be used to contain any corrosive substance, or where such a mixture would promote corrosion. 

A glass test tube is much more suitable for that purpose; specifically, Pyrex test tubes, which are specifically manufactured to resist corrosion, and to minimize expansion due to high heat, making breakage much less likely.

 When you buy test tubes future identification of the contents might be the last thing on your mind, but it should be one of the first because how many considerations are much more important than knowing exactly what is inside each test tube? Colored test tubes can make identification particularly easy, and so not a primary concern at some personality to the lab. The tint is usually transparent up that the contents can be easily viewed.

Typically Pyrex test tubes are used to store or mix small quantities of liquids or solids that are particularly corrosive, or will reach very high temperatures. A portion of the content could be removed and placed on a slide and examined under a microscope, or combined with the contents of another test tube as part of an experiment. 

The actual experiment could take place in one of the test tubes, combining the contents from two, three or more sources. If the combination of such chemicals would be particularly corrosive, or they would be needed to a very high temperature, Pyrex test tubes would be specifically appropriate as they are constructed to significantly more resist corrosion and breakage from high temperatures. 

As with most any other test tubes, Pyrex test tubes are extremely efficient and practical in their design, which is tube-like with straight sidewalls from top to bottom, which minimizes content loss when pouring. Pyrex test tubes are also available in a variety of tinted colors for easy identification. If you purchase tinted Pyrex test tubes, be sure that their transparent enough to easily view the contents. 

Pyrex test tubes are widely used in laboratories when heat and corrosion resistance are a prime concern, whether in a modest high school laboratory or elaborate college or corporate lab. The cost is somewhat higher, though not prohibitive, and considering the preservation of the contents, especially if bought in bulk, Pyrex test tubes are virtually indispensable.

The construction of a test tube rack might be determined by it use i.e. corrosion resistant material. The four main rack construction materials are plastic, polyethylene, metal and wood. Plastic, being very economical is often used; polyethylene for acid and corrosion resistance, metal is more sturdy, and better wearing under certain circumstances, while wood might be chosen for aesthetics. There are even cardboard throwaway racks. 

The test tube capacity could be as little as 4 to 8, or as many as 60 to 80, or more. Some test tube racks are stack-able. They are available in a variety of colors, just like test tubes. Some people value aesthetics, even in a laboratory, and color coordination is a consideration. 

A test tube rack may also have pins on which the tubes may be inverted to drain and dry after cleaning. This can be particularly convenient if the drainage pins are on the same rack on which the test tubes are stored. Considering that test tube racks are relatively a rather inexpensive piece of equipment, most likely you would be able to choose and purchase exactly the model that would be most appropriate for your lab i.e. a rack constructed of special noncorrosive material, a particularly large rack, a wooden rack etc.  

Performing a search on the Internet among the many manufacturers and sellers of test tube racks, and the appropriately matching test tubes, will provide you with a seemingly endless choice from which obviously you could find exactly the test tube rack or racks that would be a perfect fit for your lab.

The appropriate content stored in plastic test tubes can be transferred to a slide and placed under a microscope, or added to another test tube for mixture. As such, an entire experiment could take place within a single test tube. The singular or mixed content of two or more other test tubes could all be combined in one; there the reaction in the experiment could be observed. 

In such a mixture of glass and plastic test tubes it is very important that the limitations concerning heat and corrosion be kept in mind when conducting such an experiment. Otherwise, a loss of valuable time, or of critical content itself could void any financial savings from purchasing a set or sets of plastic test tubes. 

Another use is storage of specimens and biological samples. A common example would be samples of blood types i.e. Type A, Type B etc; then transfered to a slide or study under a microscope for purity or any abnormalities. 

Plastic test tubes are a staple in most laboratories in high schools, colleges, universities and in corporate labs. They are a critical component to any fully equipped laboratory, due to their relatively small, perfectly designed physical structure for their purpose. Identification and storage of their contents is easily maintained over long periods of time. 

That “perfect” structure being tube-like, with straight sidewalls from top to bottom. That prevents virtually any loss of the content while being poured. Though most plastic test tubes are clear plastic, a large variety of colored plastic is available. This is sometimes preferred for ease of identification. A transparent tint is used so the contents would still be easily visible.

The other main use of science test tubes has nothing to do with any experimentation, but rather simply as the preferred method of storage for biological samples. Often these would be blood samples, which then could be examined and studied through a microscope for biological content and purity.

Science test tubes are a critical component in even the most basic high school laboratory, to the most elaborate and sophisticated labs in corporations, colleges and universities. They are absolutely indispensable, thanks to their very compact and efficient physical structure, ease of storage and relatively low cost compared to most other laboratory furnishings.

That extremely practical and efficient "structure" is tube-like, with sidewalls that are straight from bottom to top which keeps loss of contents to a minimum when pouring. Though most science test tubes are clear making it very easy to view the contents, some do have a color tint for easy identification and are still rather transparent.

If the science test tubes are to be used for storage and mixture in chemistry, it would most likely be constructed of glass to counter corrosive chemicals and high temperatures. If the test tubes are to be used for storing biological material, they are probably constructed of less expensive clear plastic.