Under the principle of clearness

The following observations may help to avoid accidents, especially in the case of toy fireworks. (1) The part in which the composition is loaded, 

There are many kinds of conposition, which cannot be distinguished from each other. To avoid errors due to this difficulty we must devise some method of separating them. For example, a white composition could be coloured by adding a small amount of dye to it a black conposition could be mixed with a small amount of aluminium flake. When this is impossible, clearly label the container with details of the composition. 

Finished or half finished firework components, which resemble each other and are different in use or in concent, should be made distinguishable by painting or labelling them in a different colour or with some mark etc. 

Inspection. The construction of firework pieces should be planned generally for ease of inspection. An important part should be planned so that we can see the errors in assembly from the outside. Do not use paste only, irrespective of synthetic resin or other adhesives, for jointing which must stand a large explosive force, because it is difficult to inspect whether the junktion with paste is complete or not. If the paste is used, there must be a reliable method, e.g., as shown in Fig.144(B) and (C) are reliable without any inspection (E) and (F) are inspected from the outside. 

Jointing a plastic tube and plug with synthetic paste. 

---