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Incompatible chemicals


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#1 THEONE

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Posted 29 July 2020 - 01:11 AM

I am planning to make a big bach of red and green stars with mg and nitrates. Most likely the str nitrate will react with the mg powder. Will the 1% boric acid solve that problem? Also what other incompatibilities exist and when the boric acid have to be added ? Does the boric acid have any effect on color compositions ?

I am planning to roll them with lead shots. Is there also any incompatibility with the lead metal ?

Edited by THEONE, 29 July 2020 - 01:14 AM.


#2 Carbon796

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Posted 29 July 2020 - 09:58 AM

Boric acid likely won't provide any protection for that combination. And, is likely to degrade the magnesium faster.

Boric acid is used in potassium nitrate/flake aluminum/sodium oxalate " flitter " type comps. That have a reputation for reacting. Usually due to " dirty " sodium oxalate that is alkaline.

It's better/wiser to use a non aqueous binder system with magnesium. Magnesium is protected by a potassium or sometimes ammonium dichromate coating/reaction/conversion process.

#3 THEONE

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Posted 29 July 2020 - 10:16 AM

If i keep the stars inside a desiccator bag, so they would be really dry, will still the mg react with str/ba nitrates over time?



#4 snapper

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Posted 29 July 2020 - 12:46 PM

do not use a water binder with mag, whatever solvent based binder you use make sure thee solvent is dry or dried before use or risk mg  reaction



#5 MadMat

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Posted 29 July 2020 - 01:19 PM

I have always used Mg that was treated with potassium dichromate to prevent unwanted reactions. Some people use linseed oil to coat Mg, but I consider it messy and it can screw up your fuel/oxidizer ratio in a comp. If you use either method, remember to be somewhat gentle in your handling of the treated Mg because it is a coating that can be scratched off with rough treatment. Another reason I used dichromate is that the coating is more durable than a linseed coating



#6 THEONE

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Posted 29 July 2020 - 03:00 PM

Can i use any other oil rather than linseed oil?

 

P.S. I have seen some ppl that when they make al powder, they add a bit of charcoal during milling to form a protective layer, is the same going to work with mg too?

 

 

Thanks for the info.



#7 Carbon796

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Posted 29 July 2020 - 03:23 PM

Charcoal is not going to provide a protective layer against anything. At most its acting as a sort of milling " lubricant " lampblack would be the correct milling additive. When trying to produce a dark aluminum powder. But, it's still not providing a protective layer against a chemical reaction.

#8 THEONE

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Posted 29 July 2020 - 10:09 PM

I see. Thanks Carbon for your info. So i have to use oil or dichromates. I guess that is the reson why treated mgal with dichromates is used for glitter effects, to protect the metals for reacting and destroying the effect

Edited by THEONE, 29 July 2020 - 10:13 PM.


#9 Carbon796

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Posted 29 July 2020 - 10:37 PM

Mg/Al is generally not treated for use with aqueous binding whether glitters or colors. An Al based glitter with sodium oxalate may need the use of boric acid to prevent a reaction. But, if spherical Al is used it may not need it. Since spherical Al is less reactive than flake Al. Ambient temperature during wetting can also play a role. A comp mixed while temps are in the 90's during summer may react. While the same comp mixed at 60° during the spring or fall may not show any signs of reacting.

#10 davidh

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Posted 30 July 2020 - 02:12 AM

There is a chart somewhere that shows how well different Mg coating methods protect from different oxidizers. Is it in Shimizu? Regardless, there is a published chart.



#11 davidh

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Posted 30 July 2020 - 02:14 AM

The bottom line (IIRC) was linseed oil for all but AP, and dichromate for AP.



#12 THEONE

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Posted 01 August 2020 - 10:31 AM

I am planning to use the oil for color compositions (red and greed). Is there any possibility that the oil from the mg could destroy the color?



#13 Carbon796

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Posted 01 August 2020 - 12:04 PM

Your going to want to use boiled linseed oil only, not raw.

You'll want to use about 3-5% of oil to mag weight.

Your going to want mix the linseed oil with a solvent, to get it evenly distributed into the mag.

See al93535's post here ;

https://www.amateurp...802-coating-mg/

The amount of oil compared to the total comp weight, is pretty insignificant when done correctly. Its effect on color is more than likely, also insignificant. Especially on " stronger " nitrate based colors, like red, orange, yellow, and green.

Edited by Carbon796, 01 August 2020 - 12:21 PM.


#14 Arthur

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Posted 02 August 2020 - 03:22 AM

There are too many incompatibilities in pyro chemistry for anyone to know them all at the beginning of their pyro journey.

 

Read (without posting) the forum for a month to read about other people's experiences, BUY and read at least two of the formal text books -Shidlovskiy Lancaster Weingart come to mind immediately -there are more. BUY and treasure the hardback books. 

 

It takes a lot of skill and experience to make a system of colour comps that do "all colours". Mr Veline devised probably the best system, All colours and most mixed colours, but the blues are less good than the other colours. -Good blues are difficult.

 

Starting with strontium nitrate and magnesium makes your life hard. Strontium nitrate doesn't dry and stay dry well, so will almost always mean damp stars. Magnesium is too sensitive to react in the nearly dry comp and may spontaneously ignite, magnalium is so much safer.

 

http://www.thegreenm...uk/pfp/db1.html  is one online copy of a long established formulary. If it's marked there as hazardous then IT'S Too hazardous for inexperienced builders and probably too hazardous for even the most experienced.

 

Professional use comps are built for economy! Why evaporate and lose a solvent when you could use water.






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