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still confused about what to use for wetting agent.


Chunn7704

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From what i understand when dextrin is present u use water or water and alcohol, and when parlon is present u use aceton. please correct me if im wrong on this. But what confuses me is i see star formulas with dextrin and parlon and red gum. Not sure what happened but i tried to use water with a formula that contained red gum and it turned to a solid instantly. now i have lil chunks of red gum in my cut stars. haha. someone please help, bit confused.

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The use of acetone with Parlon is in an attempt to use the parlon itself as a "secondary binder".

 

If the star formula contains dextrin, alcohol is sufficient as a "wetting agent". It will aid in wetting hydrophobic materials, and won't dissolve the parlon.

 

Lloyd

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The solutionnis much easier:

If dextrine is present, use water

 

Else if no dextrine is present, but parlon use acetone,

Else if no dextrine or parlon, but red gum use alcohol.

 

If a mix of parlon and red gum, look at the directions or decide yourself what you want to do, depending on what is your method. E.g. if you cut or pump better use acetone. If you roll better use alcohol.

Edited by schroedinger
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FORMULA IS 48 POTASSIUM PERCHORATE

.07 COPPER OXIDE

.11 STRONTIUM CARBONATE

.10 RED GUM

.12 PARLON

.08 MAGNALIUM

.04 DEXTRIN

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That's a bit slight on dex, Chunn. Dextrin usually needs to be about 5% to 6.25% of the formula in order to work well as a binder.

 

Most formulae specify the dextrin as a "plus percentage". When that's the case, the actual amount in the formula is less than the 'plus' percentage.

 

For instance, if the plus-percent value were 6.25% (common, at "one ounce per pound"), then the actual percentage would be 6.25/106.25, or 5.88%.

 

Lloyd

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ooo lordy, way over my head. i hate math. haha. i got the formula from Jotetes, in the download section, mabe i read it wrong.

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i just wana get a bright color, or bright formulas, i just watch others shells and if its bright to me i try and get the formula to it. haha. i guess im just hoping the right formulas are given.

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"...way over my head. i hate math. haha."

-----------

Better get used to the math, Chunn! It's part of the process. (*and it's ALL 'just arithmetic', not The Calculus*)

 

Lloyd

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4% Dextrin has been what I consider my standard quantity for years. I am fully aware that 5% is also standard, as are other quantities.

 

It may not be the case with all sources of dextrin, but I have never had any issues with 4%. Stars are rock hard and can easily handle a heavy flash boosting in a shell, which is the most strenuous structural requirement that I am aware I put my stars through.

 

Like I expect most pyros do, I am happy to flip between formulas in parts, ones in percentages where the dextrin/binder is included in the 100, and ones with 100% + the binder.

 

Even when it is +4% Dextrin, which according to my still half asleep brain will be the lowest actual % of dextrin at just under 4%, I have never had any issues.

 

But to go against all I've said, while I have no evidence such as a history of weak stars with 4%, if I feel like a certain star is going to get put through extreme conditions and I really, really want it to work, out of paranoia I may use 5%.

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I'm working on a gerb comp that contains Parlon and red gum and strontium nitrate. What can I use to granulate it? Strontium and water don't mix I've learned.
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Patrick,

It depends on how much red gum is there. If it's a substantial percentage (say, more than 5%), then alcohol is the way to bind that for granulation without incurring the extra drying necessary when Sr(NO3)2 is used with water.

 

But don't mistake this: There is NO incompatibility between strontium nitrate and water binding. It just takes more effort and time to dry it again.

 

Strontium nitrate is hygroscopic, but it doesn't undergo any adverse chemical changes when wet. It just likes to hold onto its water.

 

Lloyd

Edited by lloyd
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OldMarine you could also use shellack/red gum/phenolic resin dissolved in alcohol if you need a binder more. +2% binder (red gum 3-4%) is enough for granulation.
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When I pick formula to manipulate I prefer one that can be bound with water and dextrin because both are inexpensive as compared to solvents such as acetone or alcohol. Personally I avoid alcohol of this type like the plague. Some types I really do enjoy. :-) Once I recognize that all ingredients can accept distilled water than I would try the formula by adding 5 percent dextrin total even if none is called out in the original formula. It's when water cannot be used that I start to move toward other solvents.

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Lloyd, I had a devil of a time drying this nitrate and was gun shy about getting any H2O near it! I've got me a small drying box so I guess I'll give it it's first test. Thanks for answering a "stupid" question! ;-)
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Well, it WILL be reluctant and slow to dry. But in the economics of commercial manufacture, electricity for heat and time-to-dry are usually cheaper than volatile solvents, so long as you don't need the stuff "yesterday". Even the sun and wind will dry Sr(NO3)2-based compositions eventually.

 

In the amateur realm, I figure impatience may be more expensive than volatile solvents. So play that part by ear, Patrick!

 

LLoyd

Edited by lloyd
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I went with the water. My drying box is around 130° so hopefully drying won't take as long as it did to get the nitrate dry the first time. I think they dragged this batch behind the slow boat from China. Took 8 hours at 200° to get it dry. Edited by OldMarine
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OM, how humid is it at your location, and how is your drying box made? If it simply heats outside air and blows it over the stuff being dried, and you start with humid air, you're then blowing warm, humid air over your stuff. Very slow drying at best.

 

I'm a great believer in using a dehumidifier at low temps to dry stuff. My dry box has 2 small Peltier junction dehumidifiers that remove moisture and provide heat (max about 105F), all for 60 watts. As long as you don't overload it drying times are very reasonable. I can dry up to about 15 pounds of damp nitrate in 8-12 hours, and you can pop fresh charcoal stars in and they don't seem to be driven in.

 

Kevin

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I was drying the nitrate in the oven. It was so damp it was clumping like brown sugar.

My little drying box uses a ceramic disc heater but no dehumidifier. It works well for normal drying tasks but this batch of strontium nitrate was too wet for it.

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That's a bit slight on dex, Chunn. Dextrin usually needs to be about 5% to 6.25% of the formula in order to work well as a binder.

 

Most formulae specify the dextrin as a "plus percentage". When that's the case, the actual amount in the formula is less than the 'plus' percentage.

 

For instance, if the plus-percent value were 6.25% (common, at "one ounce per pound"), then the actual percentage would be 6.25/106.25, or 5.88%.

 

Lloyd

I have good results with using 2% Dex, dissolved in the water used to wet the composition.

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