The aim of this study was to determine whether it is possible to obtain better characterization of materials in order to find out if these one are suitable in Quality Assurance for direct tableting. We tried to show that a methodological approach combining chemical, physical and technological aspects could control the direct compression process. We chose orthoboric acid as a study model for the direct compression. From a chemical point of view, our findings show only one crystalline molecular structure (RX, DSC and Pycnometry) which means an homogeneous chemical system. Concerning the particular state (Sieving and Microscopic approach), granularity is very different between the two forms, ''crystalline'' ABC and ''powder'' ABP. Technological studies show a theological and mechanical difference, as it is demonstrated, on the one hand by the behaviour of the bulk powder (Volumenometer), on the other hand by the feasibility on the machine (Alternative EKO). We explain this difference of behaviour by only the granularity aspect. Consequently, we think that in this case, controling the granularity means controling this direct tableting process.