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trouble with volcanic smoke bomb

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Ruskie

Tue May 08 2018, 01:15PM

Registered Member #9290 Joined: Sat Jan 05 2013, 03:42PM
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Posts: 60

I recently made a mostly plaster small volcano with the intention of using either ammonium dichromate or a simple smoke bomb (made up of KNO3, sugar, and baking soda) for the "eruption". At the top of the volcano, I left a 2" hole and I then fitted a crater screen over the hole and coated the screen with this. However, first tests with the smoke bomb did not go very well. The bomb itself performed wonderfully, but I wasn't happy with the small holes it made in the top of the volcano. It seems like the bomb burns hot enough to melt the aluminum foil I had it enclosed within and then still enough heat to start damaging the furnace cement. Is there anything I can line the crater with to stop any further damage from the heating? I also want to be able to do the eruptions with the ammonium dichromate when it arrives. Thanks.

Sulaiman

Tue May 08 2018, 03:55PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141

A layer of sand or perlite at the bottom ?

It sounds like you will be using a lot of rather toxic, carcenogenic and expensive ammonium dichromate,
(I believe that all hexavalent chromium compounds are toxic)
more importantly,
you are going to make a HUGE volume of chromium(III)oxide
- do you have a plan to deal with storage or disposal ?

Ruskie

Tue May 08 2018, 04:42PM

Registered Member #9290 Joined: Sat Jan 05 2013, 03:42PM
Location:
Posts: 60

wrote ...

A layer of sand or perlite at the bottom ?

I don't think there's enough room for that unless I can somehow remove the chimney cement that has already hardened. It would have to be something I can layer right on top of the cement. I'm not sure this will be a problem with the (NH4)2Cr2O7 because, IIRC, the kit volcano I had as a child burned this right in the plaster made crater. I could be wrong, of course, but it sure wasn't sufficient with the smoke bomb.

wrote ...
It sounds like you will be using a lot of rather toxic, carcenogenic and expensive ammonium dichromate,
(I believe that all hexavalent chromium compounds are toxic)
more importantly,
you are going to make a HUGE volume of chromium(III)oxide
- do you have a plan to deal with storage or disposal ?

No large amounts, 30 g total. Enough for 2-3 small demonstrations. I wouldn't use it at all if I could find a heat resistant base for the other smoke bomb formula.

Sulaiman

Tue May 08 2018, 05:01PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141

OK, when I read a 2" hole at the top I imagined that it would get larger inside,
like a hollow volcano shape ;)

As a child I liked nitrate or chlorate with moist sawdust
- loads of thick white smoke with a not too hot reaction.

P.S. adding a whole or a part of one of these may be fun

Ruskie

Wed May 09 2018, 02:25AM

Registered Member #9290 Joined: Sat Jan 05 2013, 03:42PM
Location:
Posts: 60

wrote ...

OK, when I read a 2" hole at the top I imagined that it would get larger inside,
like a hollow volcano shape ;)

That's how it was until I added a screen over the hole in a concave shape, then covered it all with the furnace cement.

wrote ...
As a child I liked nitrate or chlorate with moist sawdust
- loads of thick white smoke with a not too hot reaction.

I may give that a try. Any recommendations for the saltpeter/ sawdust mix ratio?

I did have a bit better luck earlier today with another standard smoke bomb placed into the crater. This time, there didn't seem to be any cement flaking or breaking away, so perhaps I needed to let it cure longer. The only difficulty I ended up with was the slag from the burn was sticking to the cement and I had to use a screwdriver to break it away.

wrote ...
P.S. adding a whole or a part of one of these may be fun

I may just give those a try sometime. It would certainly be a lot cheaper than trying to make my own colored ones. That's how I was going to start out (making colored smoke bombs), but I quickly realized that the dyes were going to be difficult to obtain and expensive. I initially found plans online that said to melt crayons of color choice into the mix, but the smoke was still white so I knew that wouldn't work. I'll stick with white as it shows the demo good enough anyhow and maybe pick up a cheap smoke cake or two down the road from your link.

Ruskie

Thu May 10 2018, 03:33AM

Registered Member #9290 Joined: Sat Jan 05 2013, 03:42PM
Location:
Posts: 60

Just a quick update. I found a solution for a container capable of allowing the smoke bombs to burn and not melting-- that container happened to be a simple stainless steel scoop. It sort of sticks out above the crater, but I don't really care about that. I'm not sure which stainless alloy of course, but even the minimal alloy seems to have a melting point of 1325 C, more than adequate for the smoke device. Since I have also burned ground up sparklers too, I find it will also take those hotter temperatures without any trouble. Problem solved.

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