The use of linseed oil in rockets

[Aquarius]

I have read on this forum as a few others the use of linseed oil.

As I understand it, is has many uses in pyrotechnics.

I have not found them all I'm sure, and could not find a suitable thread, so I'll try my luck with a new one.

 

One of them is to coat reactive metals to prevent an exotermic reaction and possibly autoignition.

This is done by stir-frying the metal in question until the oil itself is no longer visible.

 

Another is to use it in the mix to make stronger nozzles and caps.

If added in say 5 % to weigth to a mix of bentonite and grog, it helps with the ramming process and plastisizes the clay to a harder form.

 

And a third is to mix it in ballmilled powder to make the grain easier to work with. And as with the clay, the grain supposiedly compacts harder and therefore CATO's come more seldom...

 

There are at least two forms of linseed oil commonly sold, raw and cooked. The latter I saw in the shop had also a bacteria-prohibiting ingerdient of some kind, don't know it it plays a role when mixing in different cenarios.

 

This is not a tutorial, more of an open question to the forum.

And comments or tips are more than welcome.

 

 

As a start, I tried some linseed oil to my straight ballmilled powder, and it did compact easier. If it will affect the performance I do not know, haven't static fired them yet.

[hst45]

This isn't specifically a pyro-related concern, but be cautious of how linseed oil is stored. Back-in-the-day, I would refinish my rifle stocks with boiled linseed oil. I would strip off the crappy gloss varnish finish, and apply a coat a day of linseed oil for two weeks. This yields a buttery soft, repairable, water repellent, non glossy finish.

 

The issue is the storage and disposal of the cloth rags used to apply the linseed. There are some reports of spontaneous combustion of these linseed oil soaked rags. Apparently the linseed oil in the atmosphere can generate enough heat to reach ignition temperature. I know this probably isn't a condition you would encounter in coating Mg, but it's just one more thing about which we should be cautious.

[Aquarius]

Thanks for pointing that out hst45, I had it in mind, but didn't add it 'cause I thought it to be common knowledge. But you are right all the way, linseed oil has been known to be a firestarter.

 

So far I have tried with 5 and 10 % oil added to my milled BP, no selfcombustion yet.

But I like to be on the safe side, and they are now drying in a safe place.

 

I do not know wich oil is the better, the raw or the cooked. So far it has been raw oil.

 

I'll post the results once I get to fire the darn things.

[Mumbles]

For metal coating you want the boiled product. I have heard of it being used a bit in nozzles, but never in fuel. I have heard about people using mineral oil though in their fuels and nozzle compostions.

 

Just wondering where you heard about this, if you remember. I'm always up for new pyro reading.

[asilentbob]

Yes hst45, air oxidation under the right conditions (lots of exposed surface area, somewhat insulated, just enough air flow) can lead to very high temperatures. I remember seeing some guys tests with this as a possible way to try to start a fire or cook a meal in the wilderness.. why you would have linseed oil in the wilderness though, i dont' know... This is coming from memory though. Perhaps he thought that the same air oxidation could be carried out with motor oil or something?

[rocket]

I’ve been tolled that turps soaked rags can do the same thing so I always hang them up in the open to dry and never leave them in a pile.

[Aquarius]

My static test of drivers using linseed oil was not a big hit, to say the least. The driver containing 10 % oil looked like a fountain with little sparks. The 5 %'er performed a little better, but not much.

 

Somehow it seems that the linseed oil, apart from slowing the fuel down, acted on the sparks, making the tail almost invisible.

 

Well, at least I know that it dosn't work!

 

Next is to use inseed oil in the nozzle to see if it is easier to ram and also makes the nozzle harder.

[Mumbles]

Why use so much. Oil should be added on the order of 1-3% It's like the people who add 10 or 20% dextrin to their mix, and wonder why it's slow.

[Aquarius]

My thought of adding oil has two basic goals:

 

1- To see if I can use BP straight from the mill, using oil to bind the dust. It's not a must, I can wet and granulate it, but I want to try it out.

 

2- To make a sturdier, more compact grain, thus hinder CATO's.

I am also trying with Red Gum and alcohol.

 

I know 10 % oil was too much, 5 % was "almost ok". Any less and I'm afrais I'll loose the effect of binding the dust.

I'll try 3 % oil, i believe that the smallest percentage I can add and still have some effect on binding.

[Osi]

Where i can purchase Linseed Oil

[Swede]

Xetap, I'm, not too sure about Tung oil... my gut feel is that it would work, and your test is too brutal. With that much surface area of Fe, nothing short of an incompatible, industrial rust preventatives like "corrosion-X" would prevent rust. I'd say use it and I think it'll work.

 

On Linseed, I've used it for years, but not for pyro... rather, like hst45, as a gunstock wood finish. Raw linseed takes FOREVER (weeks) to dry. Boiled linseed still takes days. That assumes you WANT the linseed to dry. I'm sure the heat accelerates drying. Perhaps a bit of Japan dryer added to the oil might help?

 

Osi, you should be able to find boiled linseed oil in almost any hardware store that carries painting supplies. It's almost all boiled oil, not raw. Raw linseed may have to be ordered, depending upon where you live. Frankly, I can't think of any reason not to use the boiled product. As a rocket adjunct, it'd certainly help as a moisture barrier and stabilizer for nozzles.

[Mumbles]

I think it'd be better to test it in conjunction with a KNO3 solution, which is where the problems generally occur. Chloride is a potent attacker of iron.