MadMat Posted October 20, 2015 Posted October 20, 2015 I seem to remember that moth balls are used for movie explosion effects. If I remember correctly, moth balls produced that orange fireball so familiar in movie explosions. Is my memory about this correct? If so, does anyone know if they use naphthalene or paradichlorobenzene?
Arthur Posted October 20, 2015 Posted October 20, 2015 SFX doesn't usually tell what the use for fireballs in each situation, I've used pure petrol, mixed petrol and diesel, I've seen all sorts of dusts uses inc cork powder! Usually you have enough budget to do some tests for the director's choice of flame shape and colour. Sometimes the challenge is to be able to do a nice fireball and then be able to reset it in a reasonable time. Naphthalene has been used for premade fireballs -buy them ready made- but now in the UK Naphthalene is on lists of not nice chemicals so it's no longer used.
Merlin Posted October 20, 2015 Posted October 20, 2015 I have heard of coffee creamer being used. Powdered Cremona over a piece of tissue over a quarter inch layer of BP fused from the side St bottom.
MadMat Posted October 21, 2015 Author Posted October 21, 2015 Yeah, they have an article on Skylighter's web site about Cremora mines. In the article they go so far as to make a list of various things that can be used in place of cremora; it's pretty informative. I've made a few of them and to anyone who wishes to try one; make it big or you will be disappointed with the results. I was just hoping that my memory is still intact with the moth ball thing.
Mumbles Posted October 21, 2015 Posted October 21, 2015 You're right with the mothballs, and naphthalene ones are the ones you want. The p-DCB ones don't burn particularly well, if I remember correctly. Most people do need to sort of "prime" the naphthalene though. This is most commonly done by using a BP/Naphthalene mix for the portion nearest the lift charge. I don't recall the exact ratios, but 25:75 would probably be a good place to start. This gets the fire going lights up everything else. I've also seen a couple people just use a BP/Naphthalene or Charcoal:Naphthalene mix for the whole thing. This keeps it free-flowing as an added advantage. Cremora mines are great when done right. There are a lot of similar products too. Cremora, or coffee creamer generically, is cheap for small amounts, but adds up when doing large effects. Powdered calf milk is typically the cheapest product to get this effect. You want the highest fat content available. My biggest complaint about cremora type fireballs is the tendency for the powder to clump up. This can leave balls of flaming "debris" coming out of the fireball and hitting the ground. Mixing in powdered charcoal works here too to help keep things from clumping. Avoiding exposure to humid environments also really helps. Screening the mix, and storing it in a sealed garbage bag would be the best choice if humidity is an issue. 1
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