acetone stars

[MadMat]

This is a two part question. I found a formula for red stars on pyrodata.com called "independence red".

For anyone not familiar with this comp it is:

50 strontium nitrate

18 magnalium

16 parlon

10 red gum

5 dextrin

After seeing the red gum and dextrin, I assumed 70/30 water/alcohol would be used to make cut stars. Suffice to say it turned out to be a clumpy, crumbly mess. Going back to the website, I read the "fine print" and it said to use acetone. Now question number 1; why would there be dextrin in a comp that uses parlon for the binder (I figure the red gum is a fuel)? Question number 2; I have heard horror stories about acetone making a sticky mess. As this is my first time using acetone, does anyone have any suggestions or tips for making cut stars with acetone?

 

Test firing a small amount of the comp, it produces a beautiful sparkly red that takes fire easily, and burns with a slight crackle to it.

Edited September 26, 2015 by MadMat

[rogeryermaw]

Horror is a strong word. First, work on wax paper and use a couple layers of it as acetone can seep through to some extent.

 

Second, acetone evaporates fast so make sure you have everything you need before you add solvent.

 

Third, work outside or with plenty of ventilation. That evaporating acetone vapor is heavier than air and can build up and is flammable.

 

Now you may experience some stringyness when you cut but you can minimize that with a knife that is well sharpened and it really isn't the end of the road when it does happen.

 

As far as dextrin in this composition, it is more than a potential binder. It has fuel value as well, but at 5% it may have been originally intended as the binder. Many comps like this have been made with and without the dextrin with minimal performance changes.

[stix]

Mat, I had similar questions in this recent and ongoing thread:

 

http://www.amateurpyro.com/forums/topic/11140-comps-including-parlon-and-dextrin/

 

I've ended up with a reasonable result.

 

Cheers.

[MadMat]

Opps! Talk about redundancy. Maybe I should read a little more before starting a new thread. I guess sometimes I just like to hear myself type

O.K. I usually make my 1/4" cut stars by wetting my comp until it is putty-like. I then roll it out on a flexible plastic cutting board using 1/4" sticks as a guide for proper thickness. I then invert the plastic cutting board over a 4 mesh screen and "push" the comp through. I have had fairly decent results doing this. I know, of course, that I couldn't use the plastic cutting board with acetone, but if I used a pane of glass in the same manner would this technique work, or would the stringiness of the acetone wetted comp be a problem? If so, I suppose I could roll the material out to 1/4", lay the 4 mesh screen over the top of it to create a pattern and then cut them, following the pattern with a sharp knife.

Edited September 26, 2015 by MadMat

[Arthur]

Once you work with acetone, Work cold -put the ingredients in the freezer! and mix in a snap top bag so that the solvent doesn't evaporate. Exactly when ready open the bag, roll and cut the stars. If you want a prime then dust the cutting board with 7FA first.

[dusty56]

Adding 5% alcohol to the acetone will help with the stringy problem. And plexiglass works for the board and won't break if you drop it.

[MadMat]

Thanks for the tips guys

[Mumbles]

I bet your flexible plastic cutting board is LDPE. It should hold up fine to acetone. People use plastic bags all the time to wet compositions wet with acetone which is also LDPE.

[MadMat]

O.K. thanks, I wasn't sure if it would hold up to the acetone or not. I'm going to try a small amount pressing through my screen. If there's any problems I'll just do the rest with a knife

Edited September 26, 2015 by MadMat

[taiwanluthiers]

If it's stringly, you used too much acetone. Get it wet enough so that it's sandy. It should not be wet at all. You will need some 1/4" thick sticks to act as a thickness guide, press the comp between 2 sheets of wax paper and use a rolling pin (with the sticks as a guide so the thickness remains consistent). When finished the star patty should be leather hard (you should be able to pick it up without it distorting or falling apart). Then when cut with a knife the stars will remain leather hard and not crumble or change shape in any way.

 

Oh, and also work small batches at a time. Only wet enough composition to make one patty that you can cut within 5-10 minutes.

 

I had the same problem and Michale Fales showed me how to do it right (when he visited Taiwan anyways)

Edited September 27, 2015 by taiwanluthiers

[MadMat]

Well my stars are done. It was a no-go (at least for me) trying to cut them by pressing my patty through a 4 mesh screen. I didn't really have any problems cutting them with a knife, I added a bit of alcohol to the acetone and noticed only minor stringiness, which was no problem since I had a fairly sharp knife. I tried priming by dusting my cutting board and the top of the patty with meal. I do notice that the cut sides are not primed, but I think I'm going to have to apply a second layer of prime anyways, since these stars seem a bit tough to light. That seems kind of strange since the comp in powder form took fire easily. I also noticed that the prime is messing with my color a little bit. I was wondering if making some meal with a combination of strontium nitrate and potassium nitrate would help that (also adding a bit of bright flake aluminum). I figure I could mist down the stars with 80/20 water/alcohol with a few percent of dextrin added and then roll the stars in the meal.

Edited September 28, 2015 by MadMat

[rogeryermaw]

they will behave diferently in the air. when you light them on the ground, they light unevenly but in a device, they are bathed in fire from all sides, lighting evenly and consuming the prime before the star lights. i dust my star comp before cutting and yes, after they are dry, roll them in meal with your binder of choice. if not having that first layer of prime coat the sides bothers you, sprinkle a bit of prime on after the horizontal cut and again after the vertical cut. it may not stick as well unless your prime has acetone soluble binder, as the stars are drying out during the cutting phase.

[MadMat]

Some interesting food for thought, thanks