55 replies to this topic

[Ubehage]

Does the 37.5:37.5:25 behave similar to the 68:30:8?

I have no idea..

 

When in powder-form, it would behave like crackling eggs; smoldering for a little while before going BANG.

When made into finished eggs, I could easily make 10mm-cubes with 70mesh MgAl. They would smolder for ~1.5 seconds and then explode with a LOUD bang. Almost like a gunshot.

 

With 150mesh MgAl, I could make very nice crackling that would explode in small potions with 1/10 seconds interval (there about) when made into 2mm thick strings.
These were AWESOME with some Titanium.

Edited by Ubehage, 26 February 2016 - 04:03 PM.

[pyrodoc]

Thanks for sharing, just need to order HD bismuth iii oxide now

[Fulmen]

I agree, this was inspiring.

 

Making BiO3 from shot seems to work fine, although it takes a while. While the metal quickly oxidizes when molten the oxide seems to passivate the surface somewhat. So I'm using a stirrer hotplate to agitate it, this disturbs the surface enough for the process to run at a decent rate. This oxide has a dark grey/black color, I assume it's BiO. It is then roasted at a cherry red temperature to convert it to Bi2O3.

 

The result is a dark greenish yellow powder with a bulk density of appr 4.5, it's probably contaminated with some tin oxide but I doubt if that is going to cause any problems. 

[Seymour]

I've never tried the 68:30:8 but in my experience the 37.5:37.5:25 behaves just like the crackle Spitfire describes, with MgAl size being able to get everything from a cloud of small pops per grain, to pieces that pop several times, to bits that all go bang just once. With very big MgAl I have achieved pieces as large as one cubic centimetre going off in one very loud bang.

Normally though it is pieces about 1mm cubed going bang once. As has been mentioned, density is a factor, I think denser grains tending towards a single bang and less dense making multiple pops more likely.

 

I usually use NC to bind but have used other binders. I don't consider the binder to be as critical as some people think.

 

All my Bismuth trioxide has been a yellowish powder, from several sources.

 

While I have not tried it, I've read that tin oxide can work in crackle. I bought some and one day I should try it out.

Edited by Seymour, 03 March 2016 - 03:12 AM.

[Fulmen]

Interesting. I've only found one passing reference (http://www.pyrotubes...cs/show/8637754), but it's worth a shot. That link also mentions antimony troxide, but as it's toxic I really don't see the benefit over bismuth.

[Seymour]

Again, I have never used Antimony trioxide but I do own some. If indeed it does work well in crackle I do see one benefit which is availability.

 

I've never come across Bismuth trioxide locally, and while it is not too difficult to find internationally, shipping is often more expensive than the product. Also on one occasion I got a phone call from the authorities saying that they had seen that I was getting it and wanted to know what I was doing with it. While I would have probably been able to get away with telling the truth, since I have a feeling that what I do has been known of by the authorities for a while before it became legal and professional, I told them that I was experimenting with unusual oxides in ceramic glazes. To my relief they said that this was on the list of uses that they had in front of them. I asked what it was that could be done with Bismuth trioxide that was of concern and they said it could be used in pharmaceuticals, which had never occurred to me.

 

Anyway, I can get Antimony trioxide as well as Tin oxide at my local pottery supplier, along with CuO and as I'm sure many forum members are aware, a whole lot else besides.

Edited by Seymour, 03 March 2016 - 10:55 PM.

[Fulmen]

You're right, availability would be a plus. For me it would be simpler to make it, and I suspect that the trick I used on Bismuth (mechanical stirring of molten metal) will work for tin as well. It's actually pewter so it should contain appr. 5% antimony, but this shouldn't be a problem.

[BlueComet24]

Seymour, were the authorities worried that you'd start synthesizing pepto-bismol? 

[AzoMittle]

This is an example of the problem i face many times. Different manufacturers/suppliers and their products. A formula that works for me might be trash when someone in the US or Australia tries it with chemicals from another supplier.

 

I used HD yellow Bismuth(III)oxide. A very fine dense powder. I had ordered LD once from the same supplier.... it was a disaster. The type i use now is from the electronics world. I have no idea what they use it for though, but it makes great crackling. I have never seen the oxide looking 'like metal' it looks more like sulfur, but very dense. 500g is just a tea cup in volume! The LD was 3 times more in volume, and lighter in color. 

 

 

I wonder if the LD stuff contained an inert filler to fluff it up. Would explain why it didn't work, the price difference, and the difference in mass.

 

 

Normally though it is pieces about 1mm cubed going bang once. As has been mentioned, density is a factor, I think denser grains tending towards a single bang and less dense making multiple pops more likely.

 

I usually use NC to bind but have used other binders. I don't consider the binder to be as critical as some people think.

 

 

What other binders have you tried? I'm thinking an SGRS/Dextrin bound version could be pressed and corned similar to black powder, in order to get denser grains.

[Seymour]

I've tried Dextrin, NC, NC/NG and Resinox.

 

I don't feel comfortable corning crackle like BP without some considerable variations in the process. I for one use quite a lot of violence corning black powder, and using a hydraulic press, and clubbing with a metal bar are standard ways for me to reduce pucks to smaller bits, but crackle is known to be extremely sensitive.

 

Indeed I had a very scary incident with it once. During granulation a quantity of mix had dried a bit and was now blocking a number of gaps in the screen, and smudging more of the dough-like wet crackle mix on it was not pushing it through. The area blocked was a few centimetres square and was enough to bug me a bit, so I decided to clear it. 

 

Scraping it with a piece of metal would have removed it easily but obviously this would be a bad idea even if it was a much less sensitive composition, and so I chose a small stick of soft wood. Scraping the soft wood on it set it off.

 

I was lucky and the sparks created did not light the rest of the composition stuck to the screen, or anything else. This is a good reminder not to have trays of BP and so on lying around where you are working. It's not hard to imagine how this could have killed me if things were a bit different.

 

I guess it is best to remove caked on crackle, and other sensitive compositions using a solvent to dissolve the binder, and not even gentle scraping with wood.

 

However, fortunately one can achieve dense enough dragon eggs just by the standard methods of granulating and gentle tumbling, or if you want mega novelty ones that are really just salutes in the form of a star, by cutting them.

 

Bluecomet24, I can only imagine that the answer to that is yes! Perhaps the drug cartels have decided to widen their range of wares to include drugs for diarrhea, indigestion, heartburn and nausea as well as the ones they are typically associated with.

Edited by Seymour, 05 March 2016 - 12:16 AM.

[Fulmen]

I'll have to agree with Seymour here, corning sounds like a truly bad idea. Wet processing is probably the only safe approach. 

[spitfire]

 

 

I don't feel comfortable corning crackle like BP without some considerable variations in the process. I for one use quite a lot of violence corning black powder, and using a hydraulic press, and clubbing with a metal bar are standard ways for me to reduce pucks to smaller bits, but crackle is known to be extremely sensitive.

 

Indeed I had a very scary incident with it once. During granulation a quantity of mix had dried a bit and was now blocking a number of gaps in the screen, and smudging more of the dough-like wet crackle mix on it was not pushing it through. The area blocked was a few centimetres square and was enough to bug me a bit, so I decided to clear it. 

 

Scraping it with a piece of metal would have removed it easily but obviously this would be a bad idea even if it was a much less sensitive composition, and so I chose a small stick of soft wood. Scraping the soft wood on it set it off.

 

 

 

This surprises me. I did a shock test just 3 weeks ago, because i was planning making a fountain with crackling. I placed some dry grains of crackle on a 34kg steel rod and slightly hammered it with a metal hammer. Nothing happened. I struck it very violently several times until it was completely mashed up. Still nothing happened. I did this test with other compositions in the past, some times it did snap. But not with crackle.

[Ubehage]

Indeed I had a very scary incident with it once. During granulation a quantity of mix had dried a bit and was now blocking a number of gaps in the screen, and smudging more of the dough-like wet crackle mix on it was not pushing it through. The area blocked was a few centimetres square and was enough to bug me a bit, so I decided to clear it. 

 

Scraping it with a piece of metal would have removed it easily but obviously this would be a bad idea even if it was a much less sensitive composition, and so I chose a small stick of soft wood. Scraping the soft wood on it set it off.

This is interesting information.  And wow, you were quite lucky there!

I guess we're in the same club then - of people who didn't think as much as we should have, but are here to tell about it 

 

Anyway.. Your post made me think.

I have a screen that I use for making small crackling eggs, and this needs to be cleaned after each use.

I usually wait untill the screen is dry. Then I dress up in protective clothes, and go outside with a steel brush and brush it clean.

Never had any incidents yet...

 

By "protective clothes", I just mean full-body covering cotton wool clothes. In this case, a thick sweater.

Edited by Ubehage, 06 March 2016 - 09:58 AM.

[Seymour]

I have also subjected crackle to much more violence than the time of the stick incident and not had it go off. I feel that this is the scary thing about explosives. Unreliable sensitivity. It makes it pretty easy to feel something is safe enough after seeing it hit with a hammer (as a common example, one that I have done) and having it not go off, but then it goes off some time from less force.

 

I still think giving a small piece of a composition a few impacts in a safe place can be a useful thing to do to get SOME idea of what you are working with, but its important not to be too confident just cos it didn't go off that time.

 

 

Ubehage, so long as you keep going outside well away from any other pyro I would still be willing to brush the mix off like that. I'm not worried by a bit of crackle going off, just the obvious risk of it setting other stuff off.

[Fulmen]

I feel that this is the scary thing about explosives. Unreliable sensitivity.

I'm not scared of high explosives at all, I could put a block of TNT under my pillow and not loose a second of sleep over it. Primaries or sensitive comps like flash is much scarier, cause even though they usually handle abuse fine sooner or later they will bite you if you're not careful.

 

 

I don't see the problem with cleaning the screens like that as long as you take appropriate precautions. As long as there isn't large amounts left in the screen the results from ignition should be manageable with proper safety gear.

[schroedinger]

Maybe try if this cracle also performs if dextrine bound, and the just pump it?

[Seymour]

 

 

I'm not scared of high explosives at all, I could put a block of TNT under my pillow and not loose a second of sleep over it. Primaries or sensitive comps like flash is much scarier, cause even though they usually handle abuse fine sooner or later they will bite you if you're not careful.

 

 

So true Fulmen. I guess I should have said "many explosives" because I agree that there are cases, in particular small (kilos not tonnes) quantities of many secondary HE's are reliably insensitive. You should have seen the look on my friends face when I put half a gram of TNT down on a brick and put a flame to it. He thought I was going to accidentally kill him. 

 

Similarly I get quite amused when I have some in my car and a friend gets worried about things like speed bumps. 

 

However I still think that even TNT can surprise you. One factory blew up and the suspected cause was a large block of booster mix being sheared. Admittedly it was TNT cut with some other stuff, but the people working there did not think such things as breaking a large piece of the explosive could initiate it.

 

Schroedinger, in my experience crackle works well bound with Dextrin. Lloyd said recently in regards to KNO3 and crackle that the MgAl can corrode and the solution is to make sure it dries fairly quickly. I can confirm that this is the case with MgAl and water in general with crackle, and it will work well until you let it sit wet for a few days and then it does stop working.

 

Or in other words, if you wet the mix and cut some stars with half the mix and let the other half dry, and then wet it the next day and keep making stars, the ones from the re-wetted mix work but not so well. Let it dry another time again and then re-wet it and they might not work at all after that.

 

I'm sure that everyone is capable of being less lazy than I was that time though, so you should be fine

[schroedinger]

Well if the mgal is the problem you could always dichromate coat it.

[flashman]

Has anyone tried using phenolic resin to bind crackle comp? Did it work for you?

Thanks

[lloyd]

Try the guys over on http://www.pyro-gear.co.uk/

 

They've done a ton of it, and have had a couple of articles published in American Fireworks News about it.  It's still a "work in progress", but seems to progress well.

 

LLoyd