It is pure KNO3, the percentages don´t mean, theres 46% K2O in there...
That's right, that means that when the product is decomposed there is 46% of the original weight in Potassium Oxide left as a dry residue.
Punisher, unfortunately this does not help in determining the purity, but what I can say form experience that agricultural fertiliser KNO3 is typically 98%. It's fine for making BP, I use it all the time because it's cheap as chips. You don't need any more pure material unless your looking for that last extra couple of ms-1 in burn speed. The biggest influence I've found is the type of sulphur you use and the quality of the charcoal.
the sulphur looks like small reformed grey hemispheres about 5mm diameter when they are milled they do look a pale yellow colour
You've got the sulphur nailed, Sulphur in that form has a Rhombic crystalline structure, and is commonly called Roll Sulphur. It is made by melting Sulphur and letting it freeze in lumps from a liquid phase; you should have a flat side and a side that looks like a sphincter, sorry could not resist
. Rhombic Sulphur is available in a powdered form but is more expensive than chips, because those chips have to be milled.
The other common form of sulphur has a monoclinic crystalline structure and is commonly called Flowers of Sulphur. This is made by the sublimation of gaseous Sulphur, and as you can imagine this method, although cheaper, introduces a significant concentration of Sulphuric acid. This in turn make Flowers more unsafe to use and should be avoided to aid safety. Flowers is cheaper because it is a powder in the first instance, and it does tempt a lot of people because of this. But it is safer to use Rhombic Sulphur.
its the same box as the garden direct sulphur chips that people have spoken about.
That's fine, even the green chips of Chempak Sulphur chips are fine for BP, and the green stuff, what ever it is has little to no effect on the performance of the BP. So it sounds like we are down to the charcoal. Which is the most difficult thing to get right.
The BP made with the GD sulfur chips does seem to leave more residue (kind of grey), so I suspect there may be some small amount of clay in them.
I had this problem before, and found that the light coloured BP was because of the Charcoal I was using; I used hard Lumpwood, and smashed it up into smaller bits to mill. I found that I still had after several hours of milling large rounded Charcoal bits like pebbles. Basically the mix was not getting enough charcoal and the Nitrate was having the most bearing on the colour. It took me a while to realize this but it is easily rectified by using smaller chunks of charcoal (I now use charcoal of a 10# to 20# grade).
There is a whole thread with hundreds of replies (can't vouch for the quality of all of them, but there is some really good advice) on making good charcoal. But just for the record and ease of access to information:
Briquettes = naff BP
(very naff BP, have you ever seen all the red/brown heavy ash that forms when having a barby with briquettes?)
Activated Carbon = OK BP
(some good reports, but it's only benefit, speeding up the CIA method of making BP, is lost when milling. Also there's no guarantee on what is in it!)
Graphite Powder = good luck
(I've tried it before and it's not pretty, it make a bloody mess and produces really slow burning BP.)
Lumpwood = good-ish to naff BP
(you need to avoid non-complete charcoal, i.e. charcoal with wood in it. If it's too hard its no good. This involves sifting through it by hand and pre-crushing it up into bits that your mill can handle. You have to work hard to get good BP from cheap Lumpwood form ASDA or Tesco.)
Artists Charcoal sticks = good BP
(some people swear by it but they are fools for spending that much money on it, it's a bit like a big corporation throwing money at the problem and hoping it goes away.)
Home-made/Good-Quality Soft Charcoal = good to v.good BP
Home-made Willow Charcoal = High Performance BP
(most common charcoal for making high performance BP. Take a bit of time and effort but once you've got it nailed you get kick arse BP)
Home-made Plum Charcoal = DB's BP
(there are some charcoals that are better but are even harder to come by than plum wood. I've made a small batch of BP with Plum before and it's great, pulls the pants down on any commercial lumpwood)
Basically, it sounds like your charcoal is to blame, but a little time/effort will solve that, it took me years of on/off attempts to nail it good. Here is my milling technique that I use now. I always use granular chemicals to minimise mess/dust.
I typically use for good BP:
Sulphur chips.
Granular Charcoal (10# to 20#); this aids milling and makes less mess than airfloat charcoal, as a rule I don't put anything bigger than 10mesh into the mill.
98% KNO3.
1. Weigh out everything.
2. Put the sulphur chips in the mill for an hour. Check it is powder and no bits, if not mill for longer.
3. Put charcoal in mill and mill for an hour. Check it is powder and no bits, if not mill for longer.
4. Add the KNO3 to the mill for another hour and done!
A good little test is to burn a little and not only note the speed but the residue. High performance BP should leave nothing other than light burn marks or small amounts of black or white residue. As a rough guide; if it leaves a black residue there was too much charcoal in the mix, whitish yellow residue means to much Sulphur and a red residue is too much KNO3. It should go up in one quick puff and not flare or burn for too long, 1/2 second is too long. When it burns fast and you have only a little residue (a light speckling), you've cracked it.
Sort out your Charcoal and I reckon that you'll crack it sooner rather than later.
Good Luck...
This topic is locked
