47 replies to this topic

[Jerronimo]

Buy a electric coffeemill, it will reduce it to fine powder within seconds.

[Mumbles]

Shellac is too waxy to ball mill. I've heard of people getting their media caked in it from it sticking. Jerronimo is right, use a coffee grinder.

[pyrotrev]

Thanks for the advice. The stuff I have is de-waxed but is still shiny, and just damn tough!

[Steve]

I'm buying a sack of orange shellac soon. Do I want it de-waxed or not?

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For anyones future refernce, Dewaxed bleached shellac is commonly used in pyrotechnics.

Edited by Steve, 18 June 2007 - 12:45 PM.

[paul]

You want!

[Potassium chlorate]

Picking up an old thread again: I heard that the drying time is usually shorter if you use water as main solvent and dextrin as main binder than if you use alcohol as the only solvent and shellac as the only binder. Could this really be correct? I know that shellac do take a long time to dry when moistured with alcohol, but it seems illogical to me that dextrin/water should dry faster, since alcohol vapourizes much faster than water.

Does anyone know?

[digger]

Picking up an old thread again: I heard that the drying time is usually shorter if you use water as main solvent and dextrin as main binder than if you use alcohol as the only solvent and shellac as the only binder. Could this really be correct? I know that shellac do take a long time to dry when moistured with alcohol, but it seems illogical to me that dextrin/water should dry faster, since alcohol vapourizes much faster than water.

Does anyone know?

You would have thought that would be the case. However it is my experience that water bound compositions dry more quickly. This may down to a number of reasons.

With solvent bound comets I find that an impervious skin forms at the surfaces that the solvent has a hard time diffusing through. A bit like when you are painting, if you get a drip it remains soft for quite some time after the rest has dried. However the surface layers do dry more quickly than with dextrin etc. I would guess solvent bound would be fine for thin lances and small stars.

With water bound it does not appear that the outer dryer part of the composition impedes the diffusion/capillary action of the water (yes things can become bound in, but force drying solves this). A further bonus of water bound items is that they can be force dried more easily. I use a drying cabinet and that operates at low humidity and 30ºC which really speeds drying up. However I can't use it with solvent based items as an explosive atmosphere could build up in it from the vapours.

[digger]

P.S. I have just taken delivery of 250kg of ultra blonde dewaxed powdered Shellac. I will knocking some out soon at far lower prices than any of the usuall sources (woodworking etc).

[Peret]

I had a bad experience making stars with shellac using alcohol as a binder. It dissolves in alcohol rather slowly, so it's easy to do what I did and add too much liquid. Everything seemed fine at first, but then my stars dissolved into a sort of explosive, toxic amoeba that formed a skin and dripped over the edge of the tray. It took a week before it dried firm enough to handle. To anyone contemplating using it, I suggest moistening the comp with alcohol very slightly at first and letting it sit half an hour before you decide if it needs any more.

[Steve]

FYI, there have been a number of consecutive shellac crop failures, prices are currently on a steep rise.

Digger: I may be interested in 50kg of your grade of Shellac, could you PM me a price inc. Delivery to Guildford.

Do you have any reservations on storing that much powdered shellac? The dewaxed flake stuff I have has a tendancy to 'set', but being flakes, is easy to break up again, I dread to think what a 25kg bag of powder would be like to break apart once set. Or are you planning on selling it quickley? Any free-flow agents added?

[Potassium chlorate]

I had a bad experience making stars with shellac using alcohol as a binder. It dissolves in alcohol rather slowly, so it's easy to do what I did and add too much liquid. Everything seemed fine at first, but then my stars dissolved into a sort of explosive, toxic amoeba that formed a skin and dripped over the edge of the tray. It took a week before it dried firm enough to handle. To anyone contemplating using it, I suggest moistening the comp with alcohol very slightly at first and letting it sit half an hour before you decide if it needs any more.

Though I think that's almost always the case, whether you use water, alcohol, acetone or anything else: it's very easy to use too much liquid and ruin the comp. One exception seems to be pumped stars bound with SGRS, where it's easy to use too little, so that the SGRS isn't activated properly.

[Potassium chlorate]

I tested both shellac itself once again and dextrin as binders. No matter what I use, the stars are hard to ignite, though they're extremely beautiful once ignited. I had to use Hardt prime#6 and BP on top of that. How on earth did they ignite shellac bound stars in the old days before aluminium, magnesium and silicone were in use? Or is it just barium chlorate that is so hard to ignite in this "binary" composition?

Electric greens with barium chlorate, red gum, parlon and magnesium catch fire without any prime at all, but I don't think the colour is superior, only the emittance (yes, I know that I have been debating this in a few threads now, but barium chlorate fascinates me).

[starseeker]

P.S. I have just taken delivery of 250kg of ultra blonde dewaxed powdered Shellac. I will knocking some out soon at far lower prices than any of the usuall sources (woodworking etc).

Have you found time to start knocking this out Gareth?

[Bonny]

I had a bad experience making stars with shellac using alcohol as a binder. It dissolves in alcohol rather slowly, so it's easy to do what I did and add too much liquid. Everything seemed fine at first, but then my stars dissolved into a sort of explosive, toxic amoeba that formed a skin and dripped over the edge of the tray. It took a week before it dried firm enough to handle. To anyone contemplating using it, I suggest moistening the comp with alcohol very slightly at first and letting it sit half an hour before you decide if it needs any more.

I've had exactly the same thing happen in the past. I also experienced the skin forming, and the stars took weeks to dry. The best way I found to use shellac was to dissolve it in alcohol first (weigh what you need and add the alcohol) let it sit overnight and you should have a solution (add more alcohol if needed and wait or shake/stir) then add to the comp.

[Potassium chlorate]

With finely pulverized shellac you can roll it. It's harder than rolling dextrin bound stars but way easier than rolling parlon bound ones.

Anyway I think that a prime with 1:1 of barium chlorate/shellac and H3+10% silicon or MgAl will do for ignition.