This is a clue

Last night I mixed up some Boomerite for more tests. I wanted to answer the question as to why it goes dead after some time has passed. I did some tests in January without getting a conclusive clue. Tonight I performed the experiment I suggested in the previous post. I put some of the targets in a cooler and kept them at ice temperature and I kept other targets warm. The targets in January were kept at about 70F for 26 hours. This time the hot targets spent the night wrapped up in two coats on top of a hot water bottle then put out in the sun for the day. I didn’t measure the actual temperature because I just wanted to see if the temperature made a difference.

Another thing I did was that for some of the targets I used plastic baggies for the Boomerite of instead of the shrink wrap on the outside of the boxes. Unfortunately the targets in cold storage got completely soaked when the ice bag leaked. Only the cold stored targets that used zip lock baggies could be tested.

The total storage time from mixing until testing was about 23 hours.

In the results below the number represent the range in yards using my .22 with Stinger ammo that the given result occurred. The estimated velocities for the various ranges at the altitude and temperature I was experiencing are

  • 11 yards => 1455 fps
  • 15 yards => 1429 fps
  • 20 yards => 1397 fps
  • 23 yards => 1378 fps
  • 25 yards => 1366 fps
  • 30 yards => 1335 fps
Stored Sealed In Result
Hot Shrink wrap 23 pop
Hot Shrink wrap 13 dud, 11 pop
Hot Shrink wrap 11 dud
Hot Baggie 23 dud, 12 boom
Hot Baggie 20 pop
Hot Baggie 11 boom
Cold Baggie 23 boom
Cold Baggie 25 boom
Cold Baggie 30 boom

It is very clear the cold storage preserves the Boom. There are also some strong hints the baggie storage may preserve the Boom better than the shrink wrap storage.

One conclusion that could be reached is that I need to make the Taj Mahal into a walk-in refrigerator. As brother Doug said, “That’s inconvenient.” Another is that there is a chemical reaction going on that is accelerated by temperature and that perhaps I should change the recipe such that no such reaction takes place.

As always, more tests are needed.


14 thoughts on “This is a clue

  1. My admittedly limited and fairly non-scientific understanding of the Boomerite mixture was that it had been worked up *having* some moisture in it – whether from the antifreeze, or where ever. When you packaged it in the baggies and keep it cool, it stays that way for a given interval. When you wrap the whole box in shrink-wrap instead, some of that moisture may be leached out of the mixture into the surrounding cardboard packaging, thereby altering your finely tuned mix. If you’re hitting that shrink-wrap with a heat-gun – that would accelerate the degradation. If you leave them out in the sun and let them heat up, that would accelerate the degradation. If you keep the mixture sealed and isolated in a baggie, cool and out of the sun… it works better longer. Seems to make sense… at least from the outside looking in. As far as keeping things ‘cold’ in Idaho in April or early May… never seems to be that much of a problem from what I recall 😉

    • Yep – I would also suspect that the uncoated cardboard is soaking up moisture. Joe used to have really good results in the early days, using saved up, coated milk cartons, as long as the mix was a good one.

    • Everyone I have talked to about this, especially the chemists, thinks moisture is something to avoid. Absorption into the cardboard probably isn’t a problem. More likely is that the shrink wrap isn’t a complete seal and may be letting moist air into the mixture through the cardboard. I may do some more tests sometime using some plastic wrap to get a better seal. Filling the zip-lock baggies is such a pain that I want to avoid that if I can.

      I did some tests with a thermocouple inside the box while using a heat gun to shrink the plastic wrap. It only raised the temperature a couple of degrees. The cardboard is a good insulator for the few seconds of heating.

      What I can do is keep the targets out of the sun as much as possible during production and storage. If I had easy access to dry ice (none to be found in Orofino) I would put some of that into the Taj to keep it a little cooler.

    • Definitely not. The air spaces between the particles are critical for detonation. The shock wave super heats the air and initiates the reaction. Even mildly compressed Boomerite is difficult to detonate.

      • What about a vacuum sealer (like a Food Saver), but without running the vacuum cycle? Just heat-seal the Boomerite-filled bag so it’s completely air- and water-tight.

        (This doesn’t necessarily need a “Food Saver” per se, but that’s the idea.)

        • The issues are filling the bags easily and getting the right size bags to fit into the boxes just right. I’ll look into it some for next year.

  2. Joe, how about using the plastic easter eggs and some electrical tape on the seam? Heck the eggs might be good enough without tape. Just get the ones without holes. Bright, cheap, and air proof.

    • Maybe. The jumbo size eggs are big enough for the closest targets. And there are even some bigger ones that might work for the 700 yard targets. I’ll keep looking. I really need materials which are biodegradable or is nearly totally consumed when it detonates. Another thing is how do we attached them to stakes? I’ve put them on my Amazon wish list and do the tests later this summer. Maybe the plastic will be consumed or turned to dust by the explosion.

      Thanks for the idea.

      • Did not consider the degradable aspect. In that case I would suggest biodegradable plastic cups that are en vouge here in the Soviet republic of Boulderistan. They can be had with lids. No idead how long it takes to degrade them.

  3. Pingback: Boomershoot prep | The View From North Central Idaho

  4. I’m no chemist, but I read a lot and took a chem class in high school.

    Are you using actual Ethylene Glycol purchased as such, or cheap antifreeze? It seems I was reading that automotive antifreeze was being switched over to Propylene Glycol to be safer for pets.

    If you’re buying dollar store antifreeze, you may be getting Propylene Glycol instead. In which case oxidization will slowly convert it to lactic acid, and heat will speed up the process. Of course being mixed with an oxidizer could speed that up a bit also.

    One such antifreeze, contents in section 3 of the MSDS – 94-96% propylene glycol.

    Of course, I could be totally wrong, but hey, it’s an idea. 🙂

    • I’m specifically getting Ethylene Glycol. It’s cheap antifreeze without added water.

      • Hm. There’s this – which is a study of coolant breakdown for solar systems, and EG does also break down. That would leave oxalic, glycolic and formic acids as products.

        It looks as if the o2 in air is sufficient to oxidize EG, so having it in intimate contact with a high quality oxidizer would have to speed that up. This reference says that EG exposed to air fully degrades in 10 days. –

        So if I’m following this correctly as soon as the components are mixed the EG is slowly oxidizing, giving you a reduction in available fuel, reduction in the amount of oxidizer, and the inclusion of those breakdown products. Higher temp speeds up the process. That would explain the results of your tests 🙁

        Apologies if I’m not making any sense, been awake too long.

Comments are closed.