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Cast from a cast


Just curious if there has ever been any research done/anything published on a procedure and the best material to produce a cast from a Mikrosil/Forensic Sil cast.  Whatever material used would obviously need to maintain the microscopic marks, have good contrast, set fairly quickly, and not stick to the Mikrosil/Forensic Sil...

Anya Sanko
Las Vegas Metro PD
Forensic Lab

Paul Murphy:
Good Morning

It all depends what you are trying to reproduce.  I have done lots of "double castings" of fired bullets and cartridge cases, however mikrosil and the other casting materials are not the best to make molds with.  I use a German product called Elastosil M4641 A and M4641 B to make microscopic quality molds of fired bullets and cartridge cases.  Obviously the molds are a "negative" of the fired bullets and cartridge cases.  To make the "positive" I use a 50/50 resin called Smoothcast 321.  In order to color the cast I use So-strong black tint (it is available in many colors).  If you have any more questions feel free to contact me at :

Paul J Murphy
Senior Firearms Technical Advisor/Forensic Firearm Examiner
Forensic Technology WAI 

That is exactly the info I was looking for, thanks.

What I am looking at doing is a consecutively manufactured bolt study and I have the ability to cast the breech faces multiple times but only a limited opportunity to test fire the bolts in the firnished firearms.  So, I need to be able to cast the few test fires that I do get (make negatives) then cast the negatives so I can use the positive casts for comparison to the breech faces if that makes sense. 

Can you let me know your supplier for those products?  I contacted a company called "Smooth-On" and they recommended a product called Task 2 or Task 3 which is a polyurethane resin, which is probably similar to your Smoothcast. 

But that is exactly what I need to do is make a negative cast then make a positive from the negative so I can compare breechface cast to test fire cast.

Thanks for the info,

Anya Sanko
Forensic Scientist I
LVMPD Forensic Lab
Firearms and Toolmarks Detail


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