COATING THE PLATE WITH COLLODION.
These matters settled, the collodionisiug of the plate may be proceeded with. A pool is poured in the centre of the plate about one-third its area, and flowed first to the top right-hand corner, then to the top left, then to the bottom left, and fin ally to the bottom right, whence the excess should be poured gently into the bottle. Do not allow the edge of the plate to touch the bottle if it can be avoided. Give the plate a gentle motion from side to side as the collodion is poured off. If the edge is allowed to grind on the side of the bottle, it will merely fill the solution with fine parti cles of glass. Directly the plate ceases to drip, replace the stopper in the collodion bottle and stand it by to set. On no ac count allow the collodion to run back en itself, or streaks and marks in the negative will be the result. In other respects, the
coating is carried out in the same way as described on p. 69. A little practice in accordance with these instructions is advis able before commencing to coat with collo dion. In coating small sizes, the plate may be supported on the tips of the fingers of the left hand, and held in position by the ball of the thumb, as shown in Fig. 159 (p. 81). When coated, the plate should be stood aside for the film to set. Setting will take a little longer in cold weather than in the summer, and may usually be determined by a dulness spreading over the film. If in doubt, the corner from which the plate was drained may be touched very gently with the finger ; if it shows no sign of tackiness, it may be taken to have set. It is then ready for immer sion in the sensitising bath.