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Author: Subject: Detonator/blasting cap numbers and their meaning
ManyInterests
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[*] posted on 22-12-2021 at 19:27
Detonator/blasting cap numbers and their meaning


I've been meaning to ask this for a while. No amount of googling or research I did ever seemed to really come up with a good answer, so I decided to open this thread to see if anyone can give me the answer...

When I was looking into detonators/blasting caps the first thing I ever hear of is the #8 blasting cap. Which is the only cap that I was able to get any clear definition of. The original #8 blasting cap was a 2 gram mixture of 80% mercury fulminate and 20% potassium chlorate. A modern equivalent is around 0.45 grams of PETN. That's all I could find.

I heard of No.10 caps, No. 3, and No. 1. All I know is that that the larger the number, the stronger the cap. So a No.1 is the weakest and is used to set off sensitive secondaries, while No. 10 is the strongest and can set off basically the most insensitive of secondaries. Or maybe I am wrong? Since they don't mention if they have a booster like RDX or PETN in the tube along with the primary.

Anyone got the information on them? I've been curious for a quite a while on this.
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Fulmen
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[*] posted on 22-12-2021 at 21:28


Davies "Chemistry of Powders and Explosives" page 414, mercury fulminate detonators:
No. 1: 0,30g
No. 2: 0,40g
No. 3: 0,54g
No. 4: 0,65g
No. 5: 0,80g
No. 6: 1.00g
No. 7: 1.50g
No. 8: 2.00g

The original detonators used straight fulminate, the chlorate mixture was a later development.

[Edited on 23-12-21 by Fulmen]




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[*] posted on 22-12-2021 at 21:35


I assume that all of these are the 80/20 mix of mercury fulminate and chlorate?

OK that makes a lot of sense really. With modern (by modern I mean 100+ year old stuff) we can achieve the same power with a much smaller amount of explosives.
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Fulmen
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[*] posted on 23-12-2021 at 06:15


Correct, todays compound detonators typically use PETN as the main charge and the reinforced head also increase performance.



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[*] posted on 23-12-2021 at 17:47


By reinforced head, I assume you mean the end of the detonator cap? Given that I am using plastic pen bodies as test caps, I am apt to agree that those need to be properly sealed otherwise the endcap will just shoot off. I tested a chlorate filled pen and it went off like a rocket when the end went off.

I noticed that some Bic pens have fairly solid end caps. Others need to have the end cap removed and a hot glue/epoxy seal put in.
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[*] posted on 23-12-2021 at 21:26


No. It means a metal cup holding the primary in the cap. You tested Chlorate and what?
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[*] posted on 24-12-2021 at 10:37


I used a 50/50 mixture of potassium chlorate and superfine (not powdered) sugar.
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