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Binders - Shellac


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#1 Sparky

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Posted 01 October 2012 - 11:27 AM

Hi all

When looking at various compositions I can see a variety of binders are often used the usual suspects are dextrin, red gum, parlon and shellac.

I know the basics such as dextrin is water activated, parlon requires acetone and is a chlorine doner, red gum is activited by alcohol etc etc.

I see a lot of older formula with shellac given as the binder but also sometimes in quite high proportions a little like parlon is. Is that because it is being used as a fuel and if I wanted to replace it with red gum or dextrin, would this be possible?

Your adviced is much appreciated as usual...

#2 pyrotrev

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Posted 01 October 2012 - 12:23 PM

Yes, that's right it's a fuel, and quite a good one with powerful oxidisers like chlorates and AP: it seems to give a nice big fairly transparent flame, likely due to it's decent hydrogen content. Mixtures with red gum will likely burn faster, but might not give such a good flame colour due to higher carbon content: though this could maybe be balanced out by replacing a proportion of the fuel by dextrin. Worth experimenting with, work out a rough oxygen budget and off you go! - let us know how you get on.
Trying to do something very beautiful but very dangerous very safely....

#3 megabusa

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Posted 01 October 2012 - 12:31 PM

I used to use shallac years ago when making stars.

As a rough guide, for mixtures using sulphur, I could sub the sulphur part weight with one containing 50:50 sulphur:shellac & it used to work fine.

This was a long time ago before I learnt about the tried & tested comps for stars !

#4 Mumbles

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Posted 02 October 2012 - 10:14 PM

Shellac tends to work better with chlorates, while red gum seems to work better with potassium perchlorate. I'm really not sure on the reason. It could be just that red gum and chlorates burn too fast/hot and denature the color. I definitely like that explanation. I've only extremely rarely seen dextrin used as a fuel. It definitely has some fuel value, but it's not nearly as much as red gum or shellac, so you'd need much more of it anyway. The few esoteric formulas I've seen where it is a fuel looked kind of amateurish anyway.

Shellac is a pain to use as a binder. It takes forever to activate, and regularly skins over and is prone to being driven in. I'd happily add a few parts dextrin and bind with water any day.

#5 megabusa

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Posted 04 October 2012 - 10:28 AM

Shellac is a pain to use as a binder. It takes forever to activate, and regularly skins over and is prone to being driven in. I'd happily add a few parts dextrin and bind with water any day.


Yep, I remeber that ! It seemed to be crumbly for ages.




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