Free U.S. Army Special Forces Guide to Unconventional Warfare by Department of the Army Page A

stopper for carrying acid.
    c. Preparation.
Fill the gelatin capsule with either water or sulfuric acid, depending on which igniter is being used. Use a medicine dropper to fill the capsule. Wipe the outside of the capsule carefully and place it on a quantity of igniter mixture.
Gelatin will slowly dissolve in either water or concentrated sulfuric acid, usually faster in water than in acid. Sulfuric acid should be handled carefully and only in glass or unchipped enamel containers.
    d. Application.
Fill a gelatin capsule with one of the igniter mixes listed under Description above. Once the liquid is added to the capsule, the next operations should be done quickly. Pile the igniter mixture on and around the capsule. Then place incendiary material in contact with the igniter mixture. (In damp weather this method should not be used with water activated igniters because premature ignition may be caused by humidity in the air.)
Use the following method in damp weather. Fill a gelatin capsule with one of the igniter mixes listed above. Be sure that both halves of the capsule fit tightly and that no igniter mix is clinging to the outside of the capsule. Place the capsule in a shallow glass or porcelain dish filled with water or concentrated sulfuric acid, depending on which type of igniter mix is used. Make sure the capsule is touching one edge of the bowl and quickly pile incendiary material close to the capsule so that when the capsule ignites, the incendiary will also ignite.
The gelatin capsule delays work slowly in cold weather and will not work at or below 32° F. Capsule thickness also affects delay time. In water at 77° F.. a delay time of approximately 20 minutes can be expected, while the same type of capsule in concentrated sulfuric acid at 77° F. will give a delay time of approximately one hour. At a temperature of 50° F., the same type of capsule will give a 6 to 8 hour delay time in water and about 24 hours delay time in concentrated sulfuric acid. Delay times become less accurate at lower temperatures.
The above listed delay times are given for one type of gelatin capsule only. Various types of capsules will give various delay times. Therefore, always check delay times for the capsule to be used.
The sulfuric acid must be concentrated. If only battery-grade sulfuric acid is available, it must be concentrated before use to a specific gravity of 1.835 by heating it in an enameled, heat resistant glass or porcelain pot until dense, white fumes appear. See paragraph 0103 for details.
    0403. RUBBER DIAPHRAGM
    a. Description.

This delay operates by the action of concentrated sulfuric acid on a thin rubber diaphragm. As the acid eats through the diaphragm, it drips onto the igniter mix and combustion results. This delay can be used to initiate the following igniters listed in chapter 3: Sugar-Chlorate (0201), Fire Fudge (0202), Sugar—Sodium Peroxide (0203), Aluminum Powder—Sodium Peroxide (0204), Match Head (0205), Silver Nitrate—Magnesium Powder (0208), and Fire Bottle (0306).
The delay does not burn or glow, a very desirable feature where premature detection may occur. The main disadvantages of this type of delay are—
(a) Delay time fluctuates with temperature changes.
(b) Delay is not reliable below 40° F.
(c) Sulfuric acid involves hazards to the operator.
    b. Material and Equipment.
    Concentrated sulfuric acid.
Thin rubber (such as balloons or condoms).
String, tape, or rubber bands.
Glass jar with glass stopper for carrying acid.
    Wide-mouthed jar or can (approximately 1 pint capacity).
    c. Preparation.
Fill the wide mouth container three-quarter full with any one of the following igniter materials:
    Sugar-Chlorate (0201).
    Fire Fudge (0202).
    Sugar—Sodium Peroxide (0203).
    Aluminum Powder—Sodium Peroxide (0204).
    Match Head (0205).
    Silver Nitrate—Magnesium Powder (0208).
Place the rubber diaphragm over the open end of the container and leave it loose enough to sag