Test Tube Wall Thickness
Being made of borosilicate glass is not a guarantee of quality of itself. Uniform test tube wall thickness is essential for safety, durability & repeated use, maximum heat transfer and chemical resistance. The average wall thickness of Indigo Instruments borosilicate glass test tubes are listed below for outside diameters (OD) of our tubes. Borosilicate glass culture tubes on the other hand are made with thin walls in order to be inexpensive & should be considered disposable test tubes.
| 13mm |
18mm |
25mm |
32mm |
38mm |
| NLA |
1.32 |
1.4 |
1.48 |
1.73 |
Note (1): We do not carry graduated test tubes with beaded rims; the closest thing we have to offer are graduated cylinders.
Note (2): We cannot guarantee our test tubes will fit your test tube rack. If this could be an issue, contact us first.
Indigo Instruments Tapered Cork Heights
Besides wall thickness, our test tubes have reinforced rims for repeated safe stoppering. Our cork stoppers are produced in Portugal using sustainable growth practices. They are a truly natural product with excellent mechanical properties (see blog below in More Info). More importantly, these stoppers are produced according to the highest cleanliness standards backed by this certificate of cleanliness & cleaning procedures.
The top row in the table below lists the nominal outside diameter of our test tubes. The bottom row is the average height of the tapered cork stoppers that fit them. There is some variance in test tube internal diameter to allow for corks to fit anywhere from 1/3 to 2/3 of their height. Since cork is compressible across its diameter, these thicknesses help ensure airtight seals no matter what the ID variance is.
| 13mm |
18mm |
25mm |
32mm |
38mm |
| NLA |
22mm (0.87") |
32mm (1.25") |
32mm (1.25") |
38mm (1.5") |
Glass Test Tube Applications
Indigo test tubes meet all the necessary specifications for use in chemistry labs. Specifically, resistance to most chemicals and thermal shock. This also makes them particularly useful in product packaging & display. Here are just a few of the uses our customers have found for our tubes. Not shown are bath salts, candy sprinkles, tea, cannabis, and wine. All tubes come with reinforced rims except where noted otherwise.
- 55907R test tube, 18 mm x 150 mm (3/4x6"), 30 mL: Shot glasses; Floral centerpiece root cuttings
- 55908R test tube, 25 mm x 100 mm (1x4"), 30 mL: Gourmet food samplers, Flower vases, Branding
- 55909R test tube, 25 mm x 150 mm (1x6"), 50 mL: Branding, Coffee, Plant propagation , Spice rack
- 55910R test tube, 25 mm x 200 mm (1x8"), 75 ml: Flower vase, Chandelier
- 55911R test tube, 32 mm x 200 mm (1.25 x 8"), 125 mL: Museum art, Spice rack
- 55912R test tube, 38 mm x 200 mm (1.5x8"), 165 mL: Concrete planter insert
Test Tubes Blogs
Borosilicate Glass Physical Properties
Borosilicate glass, sometimes referred to as "pyrex" is standard in lab glassware. It's resistant to thermal shock and is food safe because it is completely LEAD FREE compared to glass used in cut crystal, etc.!
See the tables below for physical characteristics. The first row lists the coefficient of linear thermal which is the best indicator for resistance to thermal shock . It is roughly1/3 of soda lime glass, the type most commonly used in food & drink.
| Borosilicate Glass Properties - Physical Data |
| Physical Performance |
Numerical Value |
Unit |
| Coefficient of mean linear expansion (20°C; 300°C) |
3.3 ± 0.1 |
10-6K-1 |
| Transformation Temperature |
525 ± 15 |
°C |
| Softening Point |
820 ± 10 |
°C |
| Working Point |
1260 ±20 |
°C |
| Density at 20°C |
2.23 ± 0.02 |
g/cm3 |
| Mean Thermal Conductivity (20°C-100°C) |
1.2 |
w/rn2k |
| Refractive Index |
0.92 |
1 |
No Glassware Returns
If you are unsure what glassware is best for your needs please contact us before ordering.
Glassware cannot be returned for any reason; this is for your safety and ours. It would be prohibitively expensive to test for bacteriological, chemical or radiological agents since there is no way to tell if glass has been contaminated just by looking at it. We would have to throw it away even if you claim to never have opened the package.
However, if the item is broken or clearly defective such as severely or chipped upon arrival, send us an image & we will refund you.
Safety Disclaimer-Warning
Handle glassware with care & personal protective equipment (PPE) - goggles & gloves because:
- Unless you poured it yourself, assume any liquid is hazardous.
- Hot & cold glass looks the same & does not have to be red to cause burns. Unless it was in the freezer, assume it is hot.
- Borosilicate glass will withstand a fair degree of thermal shock but unless your intent is to see if you can make it crack, don't toss recently heated glass into a cold water bath.
- When borosilicate glass breaks, it makes sharp edges like any other kind of glass. Dispose of pieces carefully.
- See blog: Glass Test Tubes with Cork-Chemistry Kitchenware which includes a video on how to safely stopper test tubes.
