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Fuses
The burning rate of this fuse is approximately 40 in. (100cm) per minute.
Material Required:
Soft Cotton String
Fine Black Powder(or Potassium Nitrate 25 parts, Charcoal 3 parts, Sulphur 2 parts)
Piece of Round Stick
Two Pans or Dishes
Procedure:
1. Moisten fine Black Powder to form a paste or prepare a substitute as follows:
A. Dissolve Potassium Nitrate in an equal amount of water.
B. Pulverize charcoal by spreading thinly on a hard surface and rolling the round stick over it to crush to fine powder.
C. Pulverise the sulphur in the sam manner.
D. Dry mix sulphur an charcoal.
E. Add Potassium Nitrate solution to dry mix to obtain a thoroughly wet paste.
2. Twist of braid three strands of cotton string together.
3. Rub paste mixture into twisted string with fingers and allow to dry.
4. Check the actual burning rate of the fuse by measuring the time it takes for a known legth to burn. This is used to determine the lenght ned for the desired time.
Slow Burning Fuses
The burning rate of the fuse is approximately 2 in. per minute.
Material Required:
Cotton String or 3 Shoelaces
Potassium Nitrate or Potassium Chlorate
Granulated Sugar
Procedure:
1. Wash cotton string or shoe lace in hot soapy water; rinse in fresh water.
2. Dissolve 1 part Potassium Nitrate or Potassium Chlorate and 1 part granulated in 2 parts hot water.
3. Soak string or shoelace in solution.
4. Twist or braid three strands of string and allow to dry.
5. Measure the actual buring rate like said above.
NOTE
The last few inches of this cord (the end inserted in the material to be ignited) should be coated with the fast burning Black Powder Paste if possible. This MUST BE DONE when the fuse is used to ignite the blasting cap.