crackle formula problems

[SharkWhisperer]

SK, indeed it's a great formula. I made one small batch of DE with mentioned formula and crackling is good. No difference from original DE forumula visibly where it uses 75% Bismuth. Great one though.

It works well. I attributed it to WB's website simply because I saw it posted there; however, others have been tinkering with reduced bismuth formulations since Bi2O3 first was introduced as a replacement for lead. You can bet the China factories are still using cheap lead tetroxide and probably bind with phenolic instead of NC. I started experimenting with phenolic bound DEs but got distracted with other projects.

[SharkWhisperer]

Let me see if I have this. I have coming -50+200 mgal coming.I want to screen the mgal and use in my mix what stays on the top of a 60 mesh screen ?

Other way around. The sizing conventions can be confusing at first, but you'll pick it up. If you screen -50+200 through a 60 mesh screen, what stays on top of your screen would be -50+60, i.e., smaller than 50 and larger than 60. Only the biggest stuff in your bag. It's probably about 10-15% of your pound of MgAl.

 

You want to take advantage of the wide range in sizes in your new MgAl. I use -60, which is probably very similar to your -50+200, except you have a few more larger particles and mine might have a bit more smaller particles (smaller than 200 mesh).

 

It'll probably work for crackle without screening at all at -50+200.

 

Or you could screen as you planned, use the MgAl that goes through your screen for DEs/crackle (this is now -60+200), and rebag the narrow range of medium-sized -50+60 MgAl from on top of your screen for use in star compositions where you might want a tight range of particle sizes! Make sense?

 

Also, i appreciate you didn't prime your earlier batches while troubleshooting, but it's a hell of a lot easier to initially prime DEs when they're a damp patty than after they're cut and hard and need rewetting.

 

I'd plan to cut them as not much bigger than 1/8" (3 mm; they'll get bigger after priming) for DEs. Mouse turds are only cut about 1 mm/side. You'll figure out your preference for different uses. Cut with a sharp knife you don't care about (metal) or a wide putty knife that you sharpened up a little. I roll mine between two pieces of wax paper using wooden square dowels (or round if that's all at hand) on the perimeters as depth guides, using a piece of PVC tubing as my roller (you can use anything cylindrical...kitchen rolling pin, smooth log...). When it's the shape and thickness you want, then lift the wax paper, liberally apply some hot prime, put the wax paper back down, and roll it into the patty some (you can also use your palms). Then cover it with something stiff like a piece of plywood or heavy cardboard (and have one underneath!), flip it over, peel back the bottom (now top) wax paper, and repeat priming on the other side. Then cut away. After cutting, I again cover the checkerboard pattern with more prime to fall down the cuts and prime the sides. Done properly, all you'll need to do is a second prime of meal powder (I heat mine up with a little metal just the same--MgAl fines and sometimes silicon) and you're finished. No need to hold the torch on them anymore.

 

I've also screen-cut DE patties before, typically using 8-mesh (1/8" hardware cloth special ordered from Ace Hardware for cheap). Can also use a 12 or 20 mesh screen for smaller crackle, but you'll need to roll your patties thinner. Screen cutting DEs benefits from good timing--there is a sweet spot between when your patties are too damp and stick to everything and cut stars stick together in piles and when the patty has gotten a little too dry and is hard to push through the screen. The first one's a bigger pia than the second one. If you go this route, have a liberal layer of prime waiting on your collecting surface and don't be afraid to add more while the patty is getting pushed through. If you have clumps of stars, let the dry a few minutes and then break them up by hand. Screens clean up with acetone. Avoid the temptation to use a wire brush--you saw what a hammer will do to DEs, even when they aren't up to spec.

 

Also, acetone evaporates pretty quickly. So a patty of DE comp can go from a sticky mess to developing a hard coating pretty quickly. This makes newbies nervous and that's when they start making mistakes. It's not a problem. Just keep a spray bottle of acetone nearby and dampen the surface with a spritz or two if needed (my primes have red gum that are soluble in acetone and alcohol). A common issue with acetone in spray bottles, is that while the bottle itself might be made out of an acetone-resistant plastic, frequently the plastic components of the sprayer guts are not. So "spray, spray, weak spray, CLOG!". Only way I know how to find out for sure is to test them--when you find one that resists acetone, then keep that aside as your acetone-only spray bottle. Don't be surprised if you wreck a few spray nozzle units finding one that is compatible with acetone. Many bottles themselves are acetone-resistant, though. Here's a chart of plastic resistance to various solvents. You want to look for those with an "A" or a "B" rating. https://www.plasticsintl.com/chemical-resistance-chart

 

Acetone isn't the only solvent you can use for DEs/NC lacquer. Methyl ethyl ketone (MEK; sold next to acetone at Home Depot) is also a good solvent for NC and crackle comps. Its advantage is that it evaporates a little more slowly than acetone, so you get a little more working time. Or you can mix the two solvents. And reportedly, adding a little isopropyl alcohol to your acetone can make your damp DE patty a little less stringy/sticky, but I've never bothered personally.

Edited August 26, 2021 by SharkWhisperer

[DALE]

Just a warning for all newbies . Do not buy your chems off Flea bay . I ordered new bi203 and cuo from chem pyro .I made a batch of d-e using the same formula as before , worked the first time, like it should . I primed a batch with pot. dichromate and green black powder . They don't look like mouse turds any more the look like 1/8 " micro globs of spiny charcoal briquettes.I May have gone overboard on the prime, but they will sure light. and they will fly out 15 ' when they go off . I want to thank Shark whisper and everyone else for all the help and good info .

[SharkWhisperer]

Just a warning for all newbies . Do not buy your chems off Flea bay . I ordered new bi203 and cuo from chem pyro .I made a batch of d-e using the same formula as before , worked the first time, like it should . I primed a batch with pot. dichromate and green black powder . They don't look like mouse turds any more the look like 1/8 " micro globs of spiny charcoal briquettes.I May have gone overboard on the prime, but they will sure light. and they will fly out 15 ' when they go off . I want to thank Shark whisper and everyone else for all the help and good info .

Mucho congrats--glad you got 'em working right! Are they popping the way you want them to? Good and loud and once/turd?

 

Only comment is I'd personally not use or consider essential toxic dichromate in a prime for any type of star. Usually I use a hot perc-based inner prime containing some silicon metal to make a molten glassy slag and a slower BP-based outer layer. But If I only had BP ingredients and metals, that would probably work just fine--I'd expect a thick layer of green mix with 10% MgAl to probably work ok. You can't "test" 'em in the firepit with an ungloved hand with dichromate on the outside:=}

 

Suggest you make a little stargun and see how they burn in flight--important to know that your prime will ignite them in motion after a burst event.

[DALE]

Ok , here is what I am doing. I take a piece if 1/8 thick mdf board. use the rough side . I make a 1 gram 50/50 mix if potassium chlor & antimony trisulfide mixed with a thick ncl. I put a penny sized dot on the mdf. Let it dry., paint a coat of elmers school glue over the mix. After all is dry put a 1/2 " diameter self adhesive red sticker . when shot with a 22lr traveling 940 fps @ 50 yards you get a Bang . Not very loud , but fun . I have been making these for 15 yrs + with no incidences . Now I want to place De in a 3 oz paper cup and get a little more fun for the grand kids .I need to see if the pot .chlor.? antimony mix will ignite the de with a heavy prime . and break the paper cup ( not to contain the de ) Not looking for anything wicked loud, I Any suggestions would be welcome

[SharkWhisperer]

Ok , here is what I am doing. I take a piece if 1/8 thick mdf board. use the rough side . I make a 1 gram 50/50 mix if potassium chlor & antimony trisulfide mixed with a thick ncl. I put a penny sized dot on the mdf. Let it dry., paint a coat of elmers school glue over the mix. After all is dry put a 1/2 " diameter self adhesive red sticker . when shot with a 22lr traveling 940 fps @ 50 yards you get a Bang . Not very loud , but fun . I have been making these for 15 yrs + with no incidences . Now I want to place De in a 3 oz paper cup and get a little more fun for the grand kids .I need to see if the pot .chlor.? antimony mix will ignite the de with a heavy prime . and break the paper cup ( not to contain the de ) Not looking for anything wicked loud, I Any suggestions would be welcome

You got your (early dysfunctional) DEs to pop with a hammer blow. Why not test the sensitivity of DEs alone to a .22 round? Might not need the chlorate/antimony at all. But your tests will be fun. Just be careful with the chlorate/sulfide comp--it'll sneak around and bite you on the ass when you're just getting comfortable with it.

 

If it worked, would be a simple thing to make disks out of DE comp for individual targets. And there's a variety of simple comps that are cheaper than Bi and Sb-containing compounds that could surround any chosen target to make a bigger boom/flash/smoke cloud.

 

Also suggest trying the reduced-Bi formulation on a batch of DEs. I cannot tell a performance difference between DEs made with 70-75% Bi vs those using equal amounts of Bi and Cu. Saves a little money.

[DALE]

I got your pm . I am normally a head down mouth shut guy . Way back when. I was using aquarium rock as a backing to set off the ignition primer .I found out it needed a shock surface THAT was risky !.I tried to prime the buggy de formula with pot chlor, mgal and red gum . I could not get enough on before they dried . The de I made with bp prime IS the 37.5, 37.5 mix , works great . I am going to try to re wet them with acetone and put another coat of primer on .I do know the dicromate is very toxic I was surprised how the pb prime worked . You may have something with the de being the ignition . I tried stars in the cup, when the bullet went thru the cup to the igniter it blew 3/4 of my stars apart . the de are smaller and I may only loose 1/2. I do value your opinions

[SharkWhisperer]

I got your pm . I am normally a head down mouth shut guy . Way back when. I was using aquarium rock as a backing to set off the ignition primer .I found out it needed a shock surface THAT was risky !.I tried to prime the buggy de formula with pot chlor, mgal and red gum . I could not get enough on before they dried . The de I made with bp prime IS the 37.5, 37.5 mix , works great . I am going to try to re wet them with acetone and put another coat of primer on .I do know the dicromate is very toxic I was surprised how the pb prime worked . You may have something with the de being the ignition . I tried stars in the cup, when the bullet went thru the cup to the igniter it blew 3/4 of my stars apart . the de are smaller and I may only loose 1/2. I do value your opinions

Cool beans. If you're repriming with a red gum-containing prime, you can use isopropyl (70% or 91%) instead of acetone and you'll have a slightly longer working time between spray and powder application. Just keep them moving when priming. A plastic bowl works fine for small batches. They'll round out, too.

 

Not surprised a cup of mouse turds got blown around. A DE sheet might be more productive. Or not. Curious if a .22 will do anything to it. Easy test.

 

For cheap backyard thrills, fill a tape-wrapped dixie cup with stars and pour BP in between, tuck a fuse in through a hole in the cup and enjoy your crackling mini-mine. Tubing for more altitude. Way better than 1.4g... Do not put face/hands over the opening during igntion, obviously.

Edited August 27, 2021 by SharkWhisperer

[DALE]

Hey shark whisper, one last question .Buggy whip de's are good , But at 50 yards away I need more pop. I screened them thru a #10 ( mouse turd size ) I have a #4 screen can I use the same comp and get louder bangs ?

[SharkWhisperer]

Hey shark whisper, one last question .Buggy whip de's are good , But at 50 yards away I need more pop. I screened them thru a #10 ( mouse turd size ) I have a #4 screen can I use the same comp and get louder bangs ?

Hi, only just saw this. No harm in trying. I make various sizes up to 1/4" cores but usually cut between 3.5-5 mm (1/8"-3/16") cores for eggs and 1-1.5 mm sizes for mouse turds/crackle with that mixed MgAl sizing, and they all seem to work fine. I usually cut patties of comp and screen sort for sizing before priming. Sreens will clean up with acetone if you use them to cut, but I just prefer not to make that mess in the first place. Others, and you, screen cut & it works fine.

 

Probably I'd try 1/8" welded stainless hardware cloth/egg cores before stepping up to 1/4". A 5' x 3' roll or 1/8" cloth can probably be special ordered from Ace Hardware or similar for cheap if it's not in stock (around here it isn't), and is enough to make many screens of any desired size. It is the most realistically priced option I've seen; certainly cheaper than McMaster or buying premade sifting screens. 1/4" hardware cloth is everywhere, and equally inexpensve.

 

With the mixed MgAl size ranges, little eggs crackle and larger ones blow without seeming prone to blowing blind and fragmenting into unburnt chunks as some large DEs can do. In general, DE mixes using a restricted range of MgAl sizes typically require a smaller mesh (perhaps -200) for tiny turds and larger MgAl grains (perhaps +100?) for larger eggs to work right without shattering. For me, it seems that using the wider size range in -60 or similar overcomes this restriction in small and medium-sized eggs.

 

You'd need to empirically test the audio differences from different sized eggs--I'm not sure sound volume scales up in direct proportion to DE size.

 

At 50 yards, I'd probably be thinking about other (cheaper but possibly more physically sensitive) comps than Bismuth-based DEs for reactive targets. There's already .22 cal reactive targets on the market that are not hard to recreate. They are going to be more sensitive than Tannerite, and require that much more additional respect and caution when using. Are you still using .22LR or a more energetic .223 round for your DE targets? Have you tried a small disk of DE comp--perhaps nickel-sized? Probably it'd just mostly shatter with a little pop, but might be fun to test, especially if you have some DE fines laying about--just remoisten in acetone and make any shapes you want. Quick n easy.

[DALE]

Thanks for the info , I will give it a try. The igniter comp I am using is relativity safe and not extremely sensitive ( a penny size drop on mdf board will ignite about anything.) You do need to have a stiff striking surface to set it off . I coat the mix with pva glue to keep it from cracking . It is not as loud as tannerite but I have stored the pre made targets for more than a year I tried a smear of the de mix on a mdf board , a target 22 ( 940 fps per sec.) will not set it off. I found that I do need a few grams of bp mixed with eggs to ignite them. The Ignition comp just blows them out ( the eggs are primed with green mix meal ).I am still in the learning curve on this pyro stuff.

[SharkWhisperer]

Thanks for the info , I will give it a try. The igniter comp I am using is relativity safe and not extremely sensitive ( a penny size drop on mdf board will ignite about anything.) You do need to have a stiff striking surface to set it off . I coat the mix with pva glue to keep it from cracking . It is not as loud as tannerite but I have stored the pre made targets for more than a year I tried a smear of the de mix on a mdf board , a target 22 ( 940 fps per sec.) will not set it off. I found that I do need a few grams of bp mixed with eggs to ignite them. The Ignition comp just blows them out ( the eggs are primed with green mix meal ).I am still in the learning curve on this pyro stuff.

Shoot, sounds like a simple fix that you already arrived at! Dump the "igniter mix" and just use BP around your eggs.

 

Would be cool if you could tune it down to a .22 8-900 fps pellet for the air rifle crowd. Gotta be super careful when you're trying to burst reactive targets with a 20 ft-lb gun, but it is do-able.

 

Bourbon might have something to chime in about .22 LRs at least. Might want to search his old threads/comments.

Edited September 12, 2021 by SharkWhisperer

[deepakpyro]

Hey shark whisper, one last question .Buggy whip de's are good , But at 50 yards away I need more pop. I screened them thru a #10 ( mouse turd size ) I have a #4 screen can I use the same comp and get louder bangs ?

Hey Dale, i made a small batch of Buggy whip DE composition. First i used 12 mesh which is too small and crackle is little as i found out later, 12# it will be nice for fountains. For shells try it through 8#. I have a good result for 8 mesh. Run it through 12# mesh and next through 6#/4# mesh so you will have +6# and -12# DE turds. I have primed using BP which is run through ball mill for 1.5 hours and added 6% of mgal and 5% Al. Its a nice crackle try that once.

Edited September 13, 2021 by deepakpyro

[SharkWhisperer]

Hey Dale, i made a small batch of Buggy whip DE composition. First i used 12 mesh which is too small and crackle is little as i found out later, 12# it will be nice for fountains. For shells try it through 8#. I have a good result for 8 mesh. Run it through 12# mesh and next through 6#/4# mesh so you will have +6# and -12# DE turds. I have primed using BP which is run through ball mill for 1.5 hours and added 6% of mgal and 5% Al. Its a nice crackle try that once.

Cool. What mesh size/range are your metals. Al type? Tx. In both your DEs and your prime, please.

Edited September 13, 2021 by SharkWhisperer

[DALE]

I used mgal -50 +200 , al -325 . rolled the patty 1/8 thick, pushed them thru a #12 screen . they light good.report is just ok .They would be louder if they were not at 3 foot ground level .

[deepakpyro]

Cool. What mesh size/range are your metals. Al type? Tx. In both your DEs and your prime, please.

For DE i use 200# mgal and 325# spherical Al and for prime 200# mgal and Indian dark Al. I used few primed stars in star mine, crackle sound is little bit suppressed due to noise cancellation feature

Edited September 14, 2021 by deepakpyro

[SharkWhisperer]

I used mgal -50 +200 , al -325 . rolled the patty 1/8 thick, pushed them thru a #12 screen . they light good.report is just ok .They would be louder if they were not at 3 foot ground level .

Edit: Disregard. Mixed up a response to Dale and Deepak's messages.

 

Mods, please delete my waste of an entry here.

Edited September 14, 2021 by SharkWhisperer

[FlaMtnBkr]

Saw this and the problem Dale was having that ended up being his Ebay bismuth oxide. I have bought bismuth before that was for pottery glaze and what I found was that the particle size was too big. It was obviously bismuth based on how heavy a small amount was but wasn't fine enough to be as reactive which resulted in only smoldering.

 

It can be ground finer which is a pain or it can mixed in with good bismuth a little at a time. I also figured out a way to make them pop by altering the other parts but it's been a long time and I'll have to find my old notebooks. If I were to guess, it was by using 325 mesh MgAl and maybe adding a little atomized aluminum but I'm not positive.