Figure 18 : Start of the mobile phase selection. First make a sample solution of about 5 to 10 weight-% in a good sample solvent as the upper concentration limit. Draw with a saturated micro brush no. 6...7 a long enough line, 80 mm... Second Dry carefully the whole thick sample line - its original thickness is seen rightmost in the figure. Third Check the detectability. If OK in day light, continue with day light but prepare for an UV-Test. If only under UV visible, take safety spectacles and prepare a working space (see the photo chamber, figure 6. Fourth Test, which solvent would work as focussing material. Start with methanol, add some traces red color in it. Fifth In figure 18 the test has been made by spotting methanol with brush no. 1 on right. Result: Methanol works perfect as focussing solvent. Now draw thick methanol lines parallel to the thick sample line. It will focus the thick original sample line into a sharp substance line as seen above. You may see: parallel line focussing has been done twice - see the shadow lines next to the red starting red focus spot. We have used micro brush 6 and a liner. Click to figure 19.