22 lines
2.0 KiB
Markdown
22 lines
2.0 KiB
Markdown
**Black powder** that passed through the steps of pressing to a known density (generally about 1.7-1.75g/ccm) and breaking down again, is finally separated by grain size using a nest of screens.
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Due to practical considerations (physical properties etc.) and with a view to simplification (comparability, reproducibility etc.) **particle size ranges** of different grades of gunpowder were standardised (although commercial manufacturers still slightly deviate from each other). Different grades show distinct burning characteristics and are used for different purposes.
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**Different grades of gunpowder (after GOEX standard)**
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|**Grade:**|**through (mesh):**|**on (mesh):**|**Particle size range (microns):**|**Popular uses (examples):**|
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|FA|3 1/2|5|5660-4000|uncommon, lifting very large calibre shells|
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|2FA|4|12|4760-1680|lifting shells, breaking cylinder shells|
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|3FA|10|16|2000-1190|lifting shells, lifting/breaking cake items, inserts|
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|4FA|12|20|1680-840|lifting shells, comets, stars, lifting/breaking cake items, shell inserts|
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|5FA|20|50|840-297|lifting stars; dipping primed crossettes, comets|
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|6FA|30|50|595-297||
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|7FA|40|100|420-149||
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|Meal D|40|-|<420|priming stars, finished devices; used in fountain/star comps; charging spolettes|
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|Fine Meal/Flour|100|-|<149|blackmatch manufacture|
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|Extra Fine Meal/Flour|140|-|<105|blackmatch manufacture|
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**On nomenclature:** The number of "F"s indicates the particle size of grain powders; the more Fs, the finer the grain. Sometimes e.g. a 4FA gunpowder is also written FFFFA, especially in some of the older publications. "A" indicates the fact that the powder contains potassium nitrate as the oxidiser, in contrast to so called "B" blasting powders using sodium nitrate, which are not normally used for fireworks. Graphite polished cannon grade powders are denoted replacing FA with "Fg", and e.g. a 4Fg shooting powder would be as fine as a 7FA fireworks powder. Fireworks powders are not normally polished, although polished grain sometimes can be found in consumer articles. |