How COARSE might powerful oxidizers and organic fuels be?

[Potassiumchlorate]

This struck me as an interesting question. My barium chlorate and potassium perchlorate are both pretty coarse but work fine. One might also see compositions (Lancaster's with Paris Green for example) where -80 mesh shellac, which is rather coarse, is recommended.

[warthog]

I have been told to make everything going to a given composition as fine as possible unless a specific mesh size if called for so that the mixture can be made as homogeneous as possible. Before I was told this I was simply using my chemicals as is besides braking up the obviously way to large clumps of course. My coms did indeed work and they worked as well as I thought possible UNTIL I went to milling everything down to as fine and even a mesh as was easily attained. When I did this as a matter of course my comps that I had thought were pretty god became really good. This sold me on this method of doing things for good.

 

While I am sure this isn't an answer to what you have asked, I did want to say this as my way of adding to the conversation. I cannot afford to waste a lot of expensive chemicals so I god for the best possible outcome every time I make something. So attempting to find out ho large a particle size will still function reasonably in a given composition seems counterproductive to me. Just my 2¢.

[Mumbles]

If you read the shellac entry when he is discussing the different chemicals, and look through the rest of the book, the answer becomes more obvious. When talking about the chemical he describes two common mesh sizes, a -30+200, and a -60+200. In the blue formula you're talking about, the pillbox star, it appears to me that he is indicating to use the 60/200 cut instead of the 30/200 cut, which you do see mentioned for other formulas. The coarser formula is present in stuff like portfires and other slower burning compositions.

 

I do not know the real particle size distribution for the shellac available to him. As you may be aware he refers to airfloat charcoal as 150mesh. If you actually look at the particle size of airfloat C, it is generally quite a bit finer than that. The shellac available from pyro suppliers in the US seems to be of the -200 mesh variety.

[Potassiumchlorate]

I have very fine shellac myself, probably at least -200 mesh, but it seems that it's almost too fine for the barium chlorate.

 

My recent barium chlorate stars burned a few seconds too long, but that is probably more due too the size of them.

[warthog]

Sorry, I misunderstood. I shall read what I need to red then and if I can actually comment I will, otherwise I shall do as usual in this sort of conversation and just read.