BP Grades and how they effect burn rates?

[Bourbon]

It needs to be fast. Just not flash fast. You mentioned comparison of yours to some on ytube vids. Some of those guys, that's all they do. They compete for fastest BP. They also spend ungodly amounts of time doing it. They have some BP that is mind blowing, but they don't actually make anything with it.

 

Like the other guys were saying. Strive for great/fast BP, but you don't have to win any records with it, unless you want to.

[Bourbon]

I'm going to have to start reading the newspaper again. Thanks to Richtee, it may actually be useful.

[Arthur]

Good BP consumes all the ingredients, bad BP leaves unconsumed ingredients so it makes less power and spits heat and fire uselessly outside the tube.

[SignalKanboom]

Are there formulas that use more than 75 percent kno3? What happens if you are .25 off on each chemical due to cheap scale?

[SharkWhisperer]

Unlikely you'd notice a difference in burn with an ingredient(s) off by 0.25%. By 2.5%, however, you might, depending on the comp.

 

There are a lot of cheap scales that give better precision than what you're suggesting. Strongly suggest calibrating any new scale (and occasional re-calibrating) against a known mass so you know how your instrument is functioning. Most modern scales, even the cheapies, are relatively precise (close values when repeatedly measuring of same mass) and accurate (measure close to actual mass present). But it's never a bad idea to confirm this, and it's fast and simple to do so. Also, some scales will be very accurate within a given range (e.g., low, medium, high weights) and less so at a different point. All scales would be expected to have maximum error at the extremes (high and low) of their stated measurement range.

 

For BP, much above approx 75% KNO₃, you're approaching an imbalance between too much oxygen released by your nitrate (thus wasted oxidizer and released oxygen) and max oxygen consumption needed by your fuel. At high temps achieved with BP using charcoal and sulfur as fuels, 1 g KNO₃ releases around 0.4 g O₂ (actually 0.396 g O₂).

 

This 75% ratio was determined over literal centuries by different groups as being closest to ideal for max effect/burn rate (assuming good, hot, reliable charcoal). Many historical military powders used this amount or less, depending on application. This is similar to current pyros using 75% KNO₃ or close for endburner rockets where only a limited surface area of the propellant is afire at any given time (the end) and 60% KNO3 BP for core-burners that have a greater surface area burning at once that would usually explode with the "hotter" BP.

 

If you're considering upping your KNO₃ above 75% to improve your BP burn rate, you're almost certainly not looking in the right direction for trouble-shooting your mix, and won't get the improvements you want.

 

<edited for typo>

Edited September 30, 2020 by SharkWhisperer

[Richtee]

I'm going to have to start reading the newspaper again. Thanks to Richtee, it may actually be useful.

Hah! Full disclosure, it was not actually NEWSPAPER, but that packing paper that’s the size of newspaper. Kinda an off white color. But I din’t see much difference between it and the perhaps more bleached newsprint. And the ink...well, I assume that can only help... But avoid the “glossy” stuff. Tried that and it was not so good.

[Mumbles]

The sheets you're talking about Rich are actually just blank newsprint usually. Same paper, none of the ink or Peanuts strips. That said, it cooks fast but isn't my favorite. It's too ashy for me, even when properly cooked.

 

In terms of alternative ratios, usually they go in a lower oxidizer, higher fuel direction. Potassium nitrate is usually decently pure, so it's usually the one reduced. When using lesser quality sulfur or a charcoal with a higher ash content, a different ratio can often improve the mix. A fairly common one in Europe is 70 Nitrate, 18 charcoal, 12 sulfur. This is particular for vine charcoal, which is known to be on the ashier side. I've brought it up recently, but some formulas given by Shimizu are in the same 70 oxidizer 30 fuel ratio and designed for use with hemp charcoal. I don't think this was a mistake, but rather a careful optimization of the materials in popular use at the time.

[SignalKanboom]

I wasnt planning on adding more. My scale is calibrated and checked frequently. I made a 10 ounce batch, so I had to break my kno3 measurements up into two separate measurements. My scale has a 100 g max, but measures to .01. I do not recall approximate error, but the scale is a cheap 11 dollar digital scale.

 

Next time I will stick to 100 gram batches. I was following the sky lighter tutorial and it makes 20 ounce batches; which at the time, I was unaware of how much that really was.

 

How do they make such strong powder in places like Thailand, or places that they definitely dont use electricity to make bp? I have seen the pass fire documentary with banana leaf and rubber band rockets.

[Richtee]

The sheets you're talking about Rich are actually just blank newsprint usually. Same paper, none of the ink or Peanuts strips. That said, it cooks fast but isn't my favorite. It's too ashy for me, even when properly cooked.

 

 

Well, maybe I was getting a little lucky? But one thing is I always paid close attention to the venting, and as soon as I seen a decrease in flame ( or slowing of smoke) out the holes I’d seal it up.

 

It’s good to see the basics being discussed again. Until you can make a decent BP, yer not QUITE a pyro It’s kinda like a bar mitzvah hahahah...

Edited September 30, 2020 by Richtee

[SignalKanboom]

Im thankful for the help from everyone.

[Bourbon]

Hah! Full disclosure, it was not actually NEWSPAPER, but that packing paper that’s the size of newspaper. Kinda an off white color. But I din’t see much difference between it and the perhaps more bleached newsprint. And the ink...well, I assume that can only help... But avoid the “glossy” stuff. Tried that and it was not so good.

Dangit, fake news man!

 

I could see how that wouldn't work with the glossy stuff. Same reason you don't use it to lite, or use it in your fireplace. Being a pit master might have helped you with not over cooking. Makes me wonder about good "heavy" packing paper.

[robbo]

Most of the paper that is made for printing and writing has clay in it. Glossy paper in particular. It prevents ink from migrating between all the cellulose fibers.

[SignalKanboom]

Most of the paper that is made for printing and writing has clay in it. Glossy paper in particular. It prevents ink from migrating between all the cellulose fibers.

Not just clay, but there are inks with metal in them often times. It should be noted, if the paper has any coatings, or ink on it that has metallic effects, do not use it. Newspaper ink is soy, so it is safe to use. Edited October 1, 2020 by SignalKanboom

[SeaMonkey]

Hah! Full disclosure, it was not actually NEWSPAPER, but that packing paper that’s the size of newspaper. Kinda an off white color. But I din’t see much difference between it and the perhaps more bleached newsprint. And the ink...well, I assume that can only help... But avoid the “glossy” stuff. Tried that and it was not so good.

That is something I've long wondered about after reading an experimenter's similar

report some years ago on using Newsprint as a source for Charcoal that produced

a Black Powder with near explosive burn rate in open air.

 

Haven't had a chance yet to make my own Charcoal from such paper for testing yet

but I have collected a fair amount of Kraft Paper Bags and Brown Cardboard to make

use of for Charcoal as soon as I can arrange it.

 

For those Muzzle-Loader shooters who use Flint-Locks this knowledge will enable

home-brew of a good fast powder for use in the pan. Quite a few are making their

own powder for the rifle, but making a good Pan Powder can be a real challenge for

the home-brewer. It has to be very fast for good reliable ignition of the main charge.

 

It's a wonder that someone hasn't gone into the business of making Charcoal from

this best kind of paper for the job. There might be a market for it.

[SignalKanboom]

Alright, I got my powder faster. Ran it for a total of 5 hours; give, or take, probably take an hour. Can I granulate powder using only dextrin as the binder? Does anyone know a good store bought screen thats about 4 mesh. I know people say window screen, but I need more specifics. What US stores, what kind, etc.. Edited October 2, 2020 by SignalKanboom

[SharkWhisperer]

Congrats on the powder improvement!

 

You can granulate with or without dextrin, depending on planned use. For lifting and bursting shells, you want the binder so the granules are hard and do not return to powder or smaller granules when handling or settling a shell on them in the bottom of a mortar. You absolutely do not want any dextrin/binder if you're using it for making rocket propellent--you still want to wet granulate to increase speed and reduce dust clouds, but it'll be difficult to compress/ram into tubes as hard granules.

 

If you're using dextrin, you definitely want to distribute it uniformly through your BP before wetting. You can alternatively mix the dextrin into your wetting water, but that requires knowing exactly how much water you'll be adding first--I never measure and am satisfied with results eyeballing water addition. Mix and eventually knead (when it's a cohesive single lump) BP well while adding water and give it a moment to distribute and be absorbed by the charcoal before adding much more so it doesn't get too wet. You want a ball that has a shiny surface, but not a patently wet surface. It should easily break ih half without losing chunks and not look wet at the fracture face. You can knead/granulate a handful at a time if the batch is large--I usually do around 200g per lump. Cover the rest of your BP dough if you're worried that it'll dry out (you can always add a little more water if need be, but shouldn't be necessary--granulating doesn't take much time). The easiest way to add powdered dextrin is to screen it into your BP before wetting. For me and most pyros I know use screens--others might mill it in (meh, why?) or hand-stir it in (takes longer to get uniform distribution and more open handling time). A cheap kitchen pasta strainer is often around 20 mesh (holes/inch) and works fine. Plenty of cheapies (make sure it's stainless steel) in the kitchen section at Walmart, Dollar store, etc. Pan screens to stop grease/bacon splatter are slightly finer mesh--probably closer to 30 (you can count holes per inch), and can be gotten at the dollar store for...$1. Catch your screenings on an appropriately sized lipped cookie sheet or in a bowl--whatever works best with your screen size/shape. You can pour it into a container, but I usually scrape it up with a spoon or spatula and tap out the last gram or two from the cookie sheet. 2 or preferably 3 repeated screenings will give great Dextrin incorporation. Or you could add it with your powder and mill a little more, but I wouldn't bother. Messes clean up fast with a damp paper towel, but try to avoid them--airfloat charcoal/BP can get everywhere by accident. If outside, careful about breezes. And BP-dust coated fingers leave nice black fingerprints everywhere--the woman gets nicked if I miss any.

 

The cheapest 4-mesh you can get is 1/4" hardware cloth/chicken fencing from Home Depot--check the Garden Section. It's probably $10-15 for a 5 x 2 foot roll. The 1/4" also comes in 3-foot widths (and 100 foot lengths) too. Cut to size with aviation/tin snips and staple to a simple wooden box or attach to bottom of a bucket or other container. They also make rolls of 1/8" (8 mesh) fencing but HD and Lowe's didn't have it; Ace Hardware was able to order it from across the country. Decent quality and a lot of extra. And much cheaper than most pyro sources for those screen sizes. I use 12" x 12" square screens for initial BP granulation of batches up to a pound or so, larger screens for more than that. Let initial granulate dry a little, and run it through the same screen again. Then spread the powder (I use fingers) into a uniform layer for even/faster drying. I granulate using 70% isopropyl alcohol (IPA) for dextrin-bound powder and 91% (70% if I don't have any 91%) IPA for no-dextrin granulating, for faster drying. Using water alone is fine, and cheaper, but takes longer to dry. When dry to the touch, it either gets screened to different mesh sizes (I most frequently separate for different uses 8-10, 10-20, 20-40, and <40 mesh powders) first or if time is short just pop it into a sealed plastic container. Either way, I add a drierite/dehydrating packet to absorb residual water overnight. If drying in the sun, take care if using shiny metal cookie sheets that you don't get any local warming/hot spots where sunlight gets focused that might cause accidental ignition--this seems to be more likely using a concave steel bowl that can focus light into discrete hotspots than with a flat cookie sheet. I've never had an issue with stainless cookie sheets/pans in direct midday sunlight. That said, you can dry them in anything--shallow plastic boxes for example. I use low-profile cookie sheets because they easily hold a pound or two of BP and low-profile allows airflow to speed evaporation. Or you can dry it in a simple drying box: the simplest is a ceramic electric heater with a fan funneled into a cardboard box containing screen boxes and a vent, to blow warm air through your comp/BP sitting on a screen (here, window screen will work). Designs are simple. Be sure no spark is possible from your heater/fan to your BP/comp! You want to dry your powder as quickly as is reasonably possible. The slower your BP dries, the bigger the KNO₃ crystals are formed (some dissolves, temperature-dependently into your added water an recrystallizes when water evaporates), which is not ideal. Fast drying=small crystals. With 70% IPA, the drying time is cut down significantly, and the 30% water is enough to activate the dextrin (I knead it for a good 5 minutes at least; if you're unsure, knead it a little more before granulating). I use 2% dextrin; others use up to 5% but I find it unnecessary and I get good hard grains. Again...no dextrin for rocket fuel.

 

<edited for clarity>

Edited October 2, 2020 by SharkWhisperer

[SignalKanboom]

Congrats on the powder improvement!

 

You can granulate with or without dextrin, depending on planned use. For lifting and bursting shells, you want the binder so the granules are hard and do not return to powder or smaller granules when handling or settling a shell on them in the bottom of a mortar. You absolutely do not want any dextrin/binder if you're using it for making rocket propellent--you still want to wet granulate to increase speed and reduce dust clouds, but it'll be difficult to compress/ram into tubes as hard granules.

 

If you're using dextrin, you definitely want to distribute it uniformly through your BP before wetting. You can alternatively mix the dextrin into your wetting water, but that requires knowing exactly how much water you'll be adding first--I never measure and am satisfied with results eyeballing water addition. Mix and eventually knead (when it's a cohesive single lump) BP well while adding water and give it a moment to distribute and be absorbed by the charcoal before adding much more so it doesn't get too wet. You want a ball that has a shiny surface, but not a patently wet surface. It should easily break ih half without losing chunks and not look wet at the fracture face. You can knead/granulate a handful at a time if the batch is large--I usually do around 200g per lump. Cover the rest of your BP dough if you're worried that it'll dry out (you can always add a little more water if need be, but shouldn't be necessary--granulating doesn't take much time). The easiest way to add powdered dextrin is to screen it into your BP before wetting. For me and most pyros I know use screens--others might mill it in (meh, why?) or hand-stir it in (takes longer to get uniform distribution and more open handling time). A cheap kitchen pasta strainer is often around 20 mesh (holes/inch) and works fine. Plenty of cheapies (make sure it's stainless steel) in the kitchen section at Walmart, Dollar store, etc. Pan screens to stop grease/bacon splatter are slightly finer mesh--probably closer to 30 (you can count holes per inch), and can be gotten at the dollar store for...$1. Catch your screenings on an appropriately sized lipped cookie sheet or in a bowl--whatever works best with your screen size/shape. You can pour it into a container, but I usually scrape it up with a spoon or spatula and tap out the last gram or two from the cookie sheet. 2 or preferably 3 repeated screenings will give great Dextrin incorporation. Or you could add it with your powder and mill a little more, but I wouldn't bother. Messes clean up fast with a damp paper towel, but try to avoid them--airfloat charcoal/BP can get everywhere by accident. If outside, careful about breezes. And BP-dust coated fingers leave nice black fingerprints everywhere--the woman gets nicked if I miss any.

 

The cheapest 4-mesh you can get is 1/4" hardware cloth/chicken fencing from Home Depot--check the Garden Section. It's probably $10-15 for a 5 x 2 foot roll. The 1/4" also comes in 3-foot widths (and 100 foot lengths) too. Cut to size with aviation/tin snips and staple to a simple wooden box or attach to bottom of a bucket or other container. They also make rolls of 1/8" (8 mesh) fencing but HD and Lowe's didn't have it; Ace Hardware was able to order it from across the country. Decent quality and a lot of extra. And much cheaper than most pyro sources for those screen sizes. I use 12" x 12" square screens for initial BP granulation of batches up to a pound or so, larger screens for more than that. Let initial granulate dry a little, and run it through the same screen again. Then spread the powder (I use fingers) into a uniform layer for even/faster drying. I granulate using 70% isopropyl alcohol (IPA) for dextrin-bound powder and 91% (70% if I don't have any 91%) IPA for no-dextrin granulating, for faster drying. Using water alone is fine, and cheaper, but takes longer to dry. When dry to the touch, it either gets screened to different mesh sizes (I most frequently separate for different uses 8-10, 10-20, 20-40, and <40 mesh powders) first or if time is short just pop it into a sealed plastic container. Either way, I add a drierite/dehydrating packet to absorb residual water overnight. If drying in the sun, take care if using shiny metal cookie sheets that you don't get any local warming/hot spots where sunlight gets focused that might cause accidental ignition--this seems to be more likely using a concave steel bowl that can focus light into discrete hotspots than with a flat cookie sheet. I've never had an issue with stainless cookie sheets/pans in direct midday sunlight. That said, you can dry them in anything--shallow plastic boxes for example. I use low-profile cookie sheets because they easily hold a pound or two of BP and low-profile allows airflow to speed evaporation. Or you can dry it in a simple drying box: the simplest is a ceramic electric heater with a fan funneled into a cardboard box containing screen boxes and a vent, to blow warm air through your comp/BP sitting on a screen (here, window screen will work). Designs are simple. Be sure no spark is possible from your heater/fan to your BP/comp! You want to dry your powder as quickly as is reasonably possible. The slower your BP dries, the bigger the KNO₃ crystals are formed (some dissolves, temperature-dependently into your added water an recrystallizes when water evaporates), which is not ideal. Fast drying=small crystals. With 70% IPA, the drying time is cut down significantly, and the 30% water is enough to activate the dextrin (I knead it for a good 5 minutes at least; if you're unsure, knead it a little more before granulating). I use 2% dextrin; others use up to 5% but I find it unnecessary and I get good hard grains. Again...no dextrin for rocket fuel.

 

<edited for clarity>

Very good post, it was easy to understand, and to read.