The articles are pulverized, and mixed by passing them through fine sieves at least twice. After the addition of linseed oil, the composition is again mixed with the hand. If too much oil be added, the port-fire will not keep. Fourteen pounds of composition, and 21/2 reams of paper, are required for 100 port-fires.
Port-fires are usually 161/2 inches, and seldom more than 21 inches in length. The paper cases must be rolled, wet with paste. The distinction, made between what is called the wet, and dry port-fire, is, that, in the former, linseed oil is used, and, in the latter, the composition is mixed dry. Dry port-fire, according to the British formula, is composed of saltpetre 4 parts, sulphur 1, meal-powder 2, and antimony 1.
The following formulæ for port fire are given in the Pyrotechny of the Encyclopedia Britannica.
| 1. | Saltpetre | 12 | oz. | ||
| Sulphur | 4 | — | |||
| Meal-powder | 2 | — | |||
| 2. | Saltpetre | 8 | oz. | ||
| Sulphur | 4 | — | |||
| Meal-powder | 2 | — | |||
| 3. | Saltpetre | 1 | lb. | 2 | oz. |
| Meal-powder | 1½ | lbs. | |||
| Sulphur | 10 | oz. | |||
| 4. | Meal-powder | 6 | oz. | ||
| Saltpetre | 2 | lbs. | 2 | — | |
| Sulphur | 10 | — | |||
| 5. | Saltpetre | 1 | lb. | 4 | oz. |
| Meal-powder | 4 | — | |||
| Sulphur | 5 | — | |||
| Sawdust | 8 | — | |||
| 6. | Saltpetre | 8 | oz. | ||
| Sulphur | 2 | — | |||
| Meal-powder | 2 | — |
Illuminating port-fires, used in fire-works for exhibition, &c. have been noticed heretofore.
The composition of the charge for fire-lances (port-fire,) is thus given by Ruggeri;
| Substances. | Proportions. | ||
| Saltpetre | 16 | parts. | |
| Sulphur | 8 | —— | |
| Powdered antimony or powdered pitcoal | 4 | —— | |
| Mixed, and passed three times through a sieve. | |||