What Is a Porosimeter?

A porosimeter is a scientific instrument that measures porous properties in sample materials. The device can provide information about pore volume, surface area, diameter, and other topics of interest. In materials testing, porosimeters can be among the equipment used to collect data. This testing can also be useful for quality control checks, oil and gas exploration, and numerous other applications where porosity could become important.

These devices work by forcing liquid or a gas into a sample at very high pressure. Mercury is a common choice of liquid, although some devices work with water. The best choice of testing material depends on the sample being tested. Porosimeters often operate in a vacuum to control air pressure as the fluid or gas is forced into the material under investigation. The amount of pressure the porosimeter needs to overcome the surface tension and push the material into the sample provides information about the porosity.

The technical specifications on the porosimeter indicate the size of the pores it can measure, based on the amount of pressure it can generate. Very high pressure is needed for small pores, and not all equipment is able to generate that level of pressure. Larger pores require less pressure, as the fluid or gas will move more readily into them. Laboratories and materials testing facilities may opt to send some samples out to specialty firms if the pores are likely to be too small for their equipment to handle.

In materials testing, porosity can be an important trait. Pore size, volume, and diameter may indicate how well the material can perform under stress. These measurements taken with a porosimeter may result in recommendations for potential uses for the material, and in the case of quality control, it may be necessary to keep materials within a narrow range. Concrete samples, for example, must adhere to rigid guidelines to be safe for use in construction of large projects like bridges and high rise buildings. Materials that are too porous could fail over time.

Lab testing can also be useful for collecting information about unknown samples. A porosimeter can offer some insight into the composition and structure of a material. This information, combined with other test data, may help researchers determine what is in a sample, and how it behaves in controlled conditions. The more data they collect, the more accurately they can pinpoint the nature of the material. A technician can write up the results for reference and review, whether a material is tested in an experiment or on behalf of a client who wants more information about it.