| Gum-arabic | 2 | oz. |
| Gum-tragacanth (powdered) | 2 | " |
| Acetic acid | 1½ | drs. |
| Glycerine | 2 | oz. |
| Water | 4 | " |
Heat the water and dissolve the gum-arabic and the gum-tragacanth, then add the glycerine and acid. Stir till thoroughly mixed, and put in a wide-mouthed bottle. This is a very good paste for sticking labels, etc., but is not good for mounting photographs. A good black ink for marking labels is made from—
| Lamp-black | 12 | grs. |
| Indigo | 4 | " |
| Copal (powdered) | 2 | drs. |
| Oil of lavender | 2 | oz. |
Heat the oil and dissolve the gum-copal in it, then stir in the lamp-black and indigo. This ink will not corrode, and it will not fade.
To prevent chemicals running down the side of the bottle when pouring, coat the rim of the bottle with paraffin wax by dipping the mouth of the bottle in the melted wax.
All trays must be washed after using. The decomposition of chemicals in an unwashed tray will often spoil fresh solutions if put into the tray. Never leave solutions standing in trays; when through using turn the solution into a glass bottle. When not in use trays should be turned upside down on a shelf or table.
Developing solutions should be filtered between each using. Bits of film often come off the plate, and if left in the developer will settle on the plate and cause a spot on the negative. The better way is to filter a solution after using and before returning it to the bottle.
To ensure perfectly clear negatives always use clean hypo. Hypo which has been used several times becomes a dark muddy color, and is apt to stain the negative. Hypo is so cheap that one can afford to use fresh, and run no risk of spoiling negatives.
In placing plates in the holders, instead of using a brush for dusting, take a piece of surgeon's cotton, roll it into a soft ball, and rub lightly over the plate. This will remove the specks of dust, and will not scratch the plate.
It often happens when travelling that a dark room is not always to be found in which to change plates in the holders. The provident amateur carries a candle with him, and when no dark room is convenient he lights the candle, sets it under a table, and changes the plates on the table. This can be done with perfect safety if care is taken that no reflected light strikes the plates. The plates being in the shadow, and the light from the candle being rather dim, the plates are not injured any more than by a red light.