In this work, we prepared different solutions of Sudan IV dye for the staining of dry films of different coatings for the preparation of microscopic sections. First, we focussed on finding suitable solvents. In the next step, the prepared solutions were used to stain the dry free films, considering the intensity of the staining and the possible decay of the films at different immersion times. The optimal solution was then used for the final staining of the microscopic sections. We used 70% and 48% ethanol, 2-propanol, turpentine and water as the solvents. The dye did not dissolve in water. The most intensive colouring was achieved with a 2-propanol solution, but the water-borne coatings dissolved in it, as was also the case when staining with turpentine solution. When immersed in a solution containing 48% ethanol, a slight colouring of the films was achieved. When using a solution with 70% ethanol, a very intense colouring of the films of all coatings occurred after only 10 minutes, and films did not decompose. For this reason, we decided to use only this solution for staining coating films when preparing microscopic sections of coated spruce wood. In this way, we have practically demonstrated the comprehensive applicability and suitability for the staining of dry coating films using a saturated solution of Sudan IV in 70% ethanol with a treatment time of 10 minutes.
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