The chemical composition of deodorant has varied over the years and is a well-studied field. The purposes of deodorant can be the reduction of sweating, the elimination of bad odors (masked by good odors), and even the elimination of bacteria. Alcohol-only-based deodorants have the possibility to induce sweating and therefore several more complex chemicals (often crystals) were introduced. However, several crystals were found to be carcinogenic . For example, the SCCS (under the European Commission) allows a concentration of merely 6 percent of aluminum in non sprayed deodorants . This post shows microscopic images of a certain deodorant and tries to assess whether the possible concentration of metals might exceed 6 percent. It is complicated to distinguish a metal in a complex structure with the only help of a foldscope, but we will make attempt to do so. Nevertheless, this post will be by no means conclusive as resources are limited. Metals inhibit the interesting property that they reflect electromagnetic waves extremely well for the whole range of the visible light spectrum. This is the reason that metals are so shiny. Therefore, at every angle at which the foldscope takes the images, the metallic parts should reflect white light. Other chemicals (such as ethanol) will vary in transparency over different reflection angles. The blue circle is the only part on the image which has indicated to have perfect reflectance over every angle and which might therefore be metallic (aluminum or others). Moreover, the different blocks in the deodorant might suggest the separation of different crystallographic domains (separated into grains), indicating the presence of other crystals such as ZnO, or more simply, NaCl. The conclusion is that the concentration of metals certainly does not exceed 6 percent in the sample of the chosen deodorant, as a very high proportion of the analyzed area is transparent at least at certain reflection angles. Also, the studied sample could contain a high amount of other crystals. Ethanol was not characterized as it would probably require more complex imaging techniques.
 Darbre PD. Underarm antiperspirants/deodorants and breast cancer. Breast Cancer Research 2009; 11 Suppl 3:S5. doi: 1186/bcr2424
 Scientific Committee on Consumer Safety (March 3, 2020). “Opinion on the safety of aluminium in cosmetic products Submission II (SCCS/1613/19)” (PDF). Retrieved May 26, 2021.