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Amount of comp needed


bob

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If I want to make 2414 cut stars that are 5/8" by 5/8" by 5/16" how much TT comp will I need in weight please. I'm milling it for one third of the time I mill my bp.

bob

 

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That´s some odd question. Why not prepare a 3lb batch or so, process it in the mill and store the rest for future use? You can dampen one portion a time, that way you won´t have surplus mass left. Or you cut more than is needed and store the stars.

 

The question can´t be answered seriously because a lot will depend on variable factors such as kind of charcoal, compression of the mass to be cut etc.

 

I don´t know for what exactly you are using the TT. I figure canister shells. From my experience these stars can be tricky to get right and will probably benefit a lot from rolling instead of cutting. I would at least consider the use of a charcoal formula intended for cut stars, such as spider star types, or charcoal streamers taken from western literature. It may still work well though.

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Sorry I didn't really write that post very well.

I have a star plate (light cover so I wont be compressing it much at all) that makes 2414 5/8" by 5/8" by 5/16" stars, if I use Spider stars (53:32:7:7 right?). I'll be use spruce charcoal, and using the stars for mines. I don't really mind having left over comp or stars but I have to make charcoal before I can make these so I just wanted a estiment.

bob

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This probably wont totally answer your question, but it might be able to provide a ballpark estimate for you. The formula is quite similar at least. When using Mike Swisher's lampblack spider composition (below), I can get about 60 pressed 1" diameter x 1.25" tall comets out of 1 kilo of composition. It's in parts, but the percentages are included for comparison).

 

KNO3 - 18 (55%)

C - 9 (27.5%)

S - 3.5 (10.7%)

Dex - 2 (6.1%)

LB - 0.25 (0.8%)

 

Each comet I make is .67 cubic inches, so that would give it a density of 24.9 g/cubic inch. You will have to remember that these comets are made with a much higher compression that you'll get in a light diffuser.

 

Each of your stars is .122 cubic inches, so the full diffuser has a volume of 294.7 cubic inches. Using the density I found, you'll need about 7338g of composition. I've found with BP, that I get about 75% of the compression by hand vs. by my press. If you estimate that your light diffuser will be filled at hand pressure, which is probably a pretty good estimate, you'll need around 5500g. Chances are this will be excess anyway due to inefficiencies in filling and compressing, but it's about where I'd start with composition amount.

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