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Magnalum / Crackle issue


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#1 Piccaso

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Posted 31 August 2019 - 10:26 PM

So I made a batch of crackling micro stars using the same formula that I used a couple of years ago and they seem to be weak. They do not pop like normal and the flashes are not quit as bright as I remember. The only difference I noticed when making this batch was when I opened my magnalum it is not as bright and shiney as when I first received it. Does any one know if it goes bad with age or could storage conditions play a part? All of the components are identical this is the only difference I have noticed.



#2 mabuse00

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Posted 01 September 2019 - 03:40 AM

I'm not 100% sure, but it seems like it does oxidise over time.

The oxide layer appears to become thicker with age.

 

(That's why I banned pure Mg from my projects, the results constantly change with oxidation level...)

 

 

The only solution is airtight storage. Airtight does NOT mean any plastic stuff where oxygen can diffuse through the walls, especially the typical ziplock bags many people tend to use.

 

 

Opinions on this subject may differ - but my recommendation: glass bottles with PTFE lids...

Heavy, bulky, but they do the trick (I think...)


Edited by mabuse00, 01 September 2019 - 03:41 AM.


#3 Yus

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Posted 01 September 2019 - 01:30 PM

Always use new magnalium. Or mill big species of Al-Mg before preparing crackling micro stars.

Al-Mg powders oxidise over time and became dark or black.

Oxidised AlMg use in prime or color comps...



#4 Piccaso

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Posted 02 September 2019 - 12:48 PM

Thank you for your responses. I always treat magnesium with dichromate  but I though most of the time MgAl was ok to leave untreated unless you where wetting it with water. I rarely use MgAl so it is not the subject I have a lot of experience with.






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