Sawdust

[Bobosan]

Been mortar rack building these couple of weeks and got a lot of sawdust accumulated. Other than TLUD for charcoal, what use does sawdust have in pyro other than packing for snap pops/sensitive devices?

[pyroman2498]

Its used more than you would think , here are a few things off the top of my head

 

1.Packing in bottoms shots in a lager shell then said bottom shot

2. Used in saettine , to hold in the black match , keep ot fire the report and makes the black match act like a time fuse instead of Quick match

3. Used in the bottom of shells to keep the bottoms flat (from my understanding

4. Filler in shells, pushed around stars to hold them in place and to make the shell much more strong and solid so nothing is rattling around

 

These are just a few things i could think of

 

Stay safe and Stay green

 

~Steven

[dagabu]

Canister shells with round inserts, to fill the spaces, make the shell hard to the touch.

[Bobosan]

I can understand how inserts might be packed in with sawdust but stars?

 

@pyroman2498 - don't stars need intimate contact with a burst or other immediate fire? Never heard the term "saettine". Guess I have some reading to do.

 

So in other cases, like bottomshots, the sawdust acts as a cushion.

[nater]

No, not really a cushion. The sawdust serves to lock the bottom shot and stars in place and keep the shell rigid. The sawdust is tamped down so that the shell does not compress when lifted. This adds the strength needed to prevent a flowerpot.

 

With stars, the sawdust is tamped in place in the triangle shaped space inbetween the stacked pumped stars and the shell casing. You can use sawdust, pulverone or even folds of paper to get the strength you need for a successful shell. The inside portion of the stars is in contact with pulverone and burst so they take fire. Some will paint a slurry prime over stacked stars before loading the cannule full of burst and pulverone filler.

[Mumbles]

I've actually never seen sawdust used for #3 in Pyroman's list. Generally polverone is just used to level things out. I'd be afraid of sawdust migrating into the rest of the shell if it were used in this manner. I've only really seen it used in the fused end of bottomshots to provide a cushion and fireblock between the outside and the flash, particularly in handrolled cases.

 

This talk of packing in inserts and stars is specifically for cylindrical inserts or comets in cylindrical shells. It is traditional to fill in all the spaces between the comet/insert and the wall of the casing with polverone or saw dust. I absolutely do this with inserts. For comets, I find that if you have enough of them (10 or so) it's not really necessary if you ensure the ring is very tight in the shell. Your own personal mileage may vary. I haven't had a failure yet, but it is a shortcut, and probably not something I'd do with more complex or larger shells.

 

Sawdust is used in some parachute shells as well to separate the bursting charge from the parachute itself. Fine sawdust is called for in the Veline Super Prime. It has shown up in some lance formulas. I've also read that some UK manufacturers used to use it to cut some of their compositions to make each batch go farther.

[Bobosan]

Thanks guys . Nowhere near cylinder shell building stage or bottom shots yet. Haven't even made a pumped star yet. Been working with different type rolled stars before moving on to ball shells. Going to TLUD the pine sawdust for now.

 

@mumbles - have seen a couple star formulas calling for wood meal, which this is not.

[WonderBoy]

I've actually never seen sawdust used for #3 in Pyroman's list. Generally polverone is just used to level things out. I'd be afraid of sawdust migrating into the rest of the shell if it were used in this manner. I've only really seen it used in the fused end of bottomshots to provide a cushion and fireblock between the outside and the flash, particularly in handrolled cases.

 

Mum, I think he was talking about the bottoms of shells, like when you roll a break over the bottom shot, you can fill in the rounded edges of the bottom shot to make the bottom of the shell square. Like this:

 

 

Although I have found this to be unnecessary, and I actually like having more of a rounded bottom on my shells. In my head it makes sense that a rounded bottom would be stronger than a flat bottom. Also, if you look at photos of shells made in Italy, many have pretty round bottoms.

 

And personally I don't use sawdust on the fused end of BS, but I do on the other side. On handrolled bottom shots, after I triangle fold the inner bag closed, I put sawdust on top of that and compress slightly to keep things tight when I place the disk on top.

 

 

WB

[nater]

I use a little bit of sawdust on the fused end of a bottom shot if it needs to be leveled off before closing with the second disc and pasting. Mostly, I use sawdust on the other end after filling and closing for the same reason as WB.

[boule]

You can also build small caliber roman candles with sawdust. Put a fuse down the side, lift powder, star, taper sawdust as a firebreak and repeat.

Additionally, there are some road flare formulas that call for sawdust as an ingredient.