One Examination of the Extraction Thimbles

Before Experiments
There are some problems with the extraction thimbles because of the manufacturing technology, which has an effect on collecting samples. The sampling error has more influence on the results of experiments than the analyzing error.
Therefore, the experimenters should select the extraction thimbles carefully before sampling for the experiments. And the translucent examination is one of the examinations for the extraction of thimbles.

Clean the inside and outside of the extraction thimble with a soft brush in order to remove the fibrous debris on the surface of the extraction thimble thoroughly.
The cleaning mentioned above will help prevent the fibrous debris from falling off when the extraction thimble is used in the lab, and meanwhile, it is also conducive to the next pinhole inspection.
For convenience, you can make a set of simple devices for the inspection.
You should make use of the small light bulb of a flashlight or LED light that is connected to the power, and wrap the light with insulating tape.
Finally, put the wrapped light into the extraction thimble.
According to the light transmission, it is easy to check whether there are pinholes on the wall of the extraction thimble and the uniformity of the fiber of the wall of the extraction thimble.