Gun Blueing

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Chemical Name:
GUN BLUEING

Surface Used On:
Brass cartridge cases.

Sensitive To:
Repelled by sebaceous components.

Development Color:	Method to Record:	Hazard:	Protective Clothing:	Fume Hood Use:
Black				Yes

Reagent Characteristics

Development Complete When:

Source of Error:

Incompatibilities:

Precautions:

Storage Container:

Safety:

Recommendations:

Similar Reagents

Sequential Reagents
(Not necessarily in this order.)

Abridged Reagent Sequence

Visual Examination
|
Cyanoacrylate
|
*** Gun Blueing ***
|
Acidified H₂0₂
|
Visual Examination

GUN BLUEING FORMULA:

Formula 44/40 
(Instant Gun Blue)

 1 part reagent to
80 parts distilled water


Outer's Gun Blue

 1 part reagent to
40 parts distilled water

PROCEDURE OF APPLICATION

1. Light fuming of cartridges
with cyanoacrylate ester.  Do not
fume in superglue chamber.

2. Immerse cartridges in
the reagent. Gently stir and roll
the cartriges in the solution.

3. Monitor closely for development.

4. Halt development by
immersing in distilled
water for 2 minutes. Air dry.

NOTE: Lacquered steel cartridges
or those cartridges with a polymer 
jacket around the casing will resist 
the oxidation/reduction resulting in 
little or no development.

Ridge Detail Visualized by:

Visible chemical/stain reaction.

Reagent Applicabilities:

Non-Porous surfaces
Post-Cyanoacrylate
Cartridge surfaces

Other Chemical Name(s):

Brass Black Metal Touch Up BB2
Formula 44/40 Instant Gun Blue
Gunslick Gun Blue
Perma Blue Liquid Gun Blue PB22
Super Blue Extra Strength

Process Summary:
Gun blueing contains cupric salt, selenious acid and an acid. Cupric ions and selenious acid are reduced by the oxidized (etched) metals of copper, aluminum, zinc & iron. The reagent etches the cartridge's metal surface not protected by sebaceous-containing latent print residue, and deposits a dark-colored Cu-Se coating to reveal friction ridge detail. Cartridges should be first briefly fumed with cyanoacrylate ester, then immersed into the gun blueing solution. A water bath stops the chemical reaction.

Accepted Deviations:
Should the over-development occur, excess gun blueing may be removed from the metal cartridge cases using acidified hydrogen peroxide. The use of cyanoacrylate fuming as a pretreatment may be skipped. A clear lacquer spray can be applied to the cartridge cases to stabilize the development process, and, to enhance the contrast of the developed friction ridge detail.

A number of gun blueing products sold under various trade names can be used in a diluted solution to reveal friction ridge detail on cartridge surfaces.

Supporting Reference Materials:
1. Minutiae Magazine, Issue No. 32, Sept.-Oct. 1995, pg. 1.
2. "Use of Acidified Hydrogen Peroxide to Remove Excess Gun Blue from Gun Blue-Treated Cartridge Cases and to Develop Latent Prints on Untreated Cartridge Cases", Cantu, A.A., Leben, D.A., Ramotowski, R., Kopera, J., Simms, J.R., Jor. Forensic Sciences, Vol. 43, No. 2, pp. 294 - 298.
3. "Evaluation of Gun Blueing Solutions and their Ability to Develop Latent Fingerprints on Cartridge Cases", The Chesapeake Examiner, Vol. 8, No. 10, October 1996.
4. "Visualization of Sebaceous Fingerpirnts on Fired Cartridge Cases: A Laboratory Study", Migron, Y.,Hocherman, G., Springer, E., Almog, J., and Mandler, D., J. Forensic Sciences, Vol. 43, No. 3, May 1998, pp. 543-548.

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