Magnetic powders are fine ferromagnetic powders applied to the latent fingerprint surface with a magnetic wand. It is a type of metallic powder that was introduced by MacDonell in 1962 along with Magna Brush. Note: Metallic powder is different from Magnetic Powders. All magnetic powders (eg: iron) are metallic powder, but all metallic
powder isn’t magnetics (eg; fine lead, bronze, etc.). Additionally, some metallic powder is dust using a glass fiber brush instead of a magnetic wand. Working: When the magnetic powder comes in the influence of a magnetic field it forms a brush that is used to dust the prints over the surface. And when a magnetic powder is applied over the latent
fingermarks, it selectively adheres to the latent prints due to its affinity for oils and moisture, leaving the substrate “paint-free.” Magnetic powders are made by the process of grinding and milling the iron grit particles to produce granular and flakes magnetic powder respectively. In any magnetic powder, there are three components: pigment and binders. They work together to provide adhesion to latent fingermarks without painting the whole surface. Note: James et al. (1991a, 1991b) demonstrated how stearic acid coating on magnetic flake powder enhances the lipophilic interaction with fatty acid of fingermarks. The optimum coating thickness stated to be 70nm. Magnetic powders are used for the development and recovery of latent prints on any non-porous and semi-porous surfaces. It is also proven that they can
develop good fingermarks even on leather, plastics, walls, and human skin. You can say, they can replace conventional non-magnetic powders. The major distinctive difference lies when it comes to texture surfaces such as oranges, non-polished woods, and leather, that have grooves or depression over their surfaces. With a textured surface, magnetic powders are more prone to stick to grooved (depressed) areas with a single stroke with minimal pressure. Conversely, the non-magnetic powders used relatively hair brushes that cause more resistance to grooved surfaces resulting in fingermarks disruption. This is the same reason why fingerprints on highly polished surfaces are dusted with magnetic powders. How to Choose Magnetic Powders Based on Surfaces?
Types of Fingerprint Powder For Latent Fingerprint DevelopmentIn general, there are four types of magnetic fingerprint powder for the development of finger marks on different surfaces. These are:
1. Magnetic Granular Fingerprint PowdersManufacturing Process and Composition: These powders have large magnetic carrier particles of metal (iron, 20–200 μm), small non-magnetic particles of metal oxides (Fe3O4, 3-12 μm), and pigment. Smaller non-magnetic pigmented particles adhere to fingermark ridges and develop fingermarks. Surfaces: These magnetic granular latent fingerprint powders are most effective on textured and polyvinyl chloride (PVC) plastic surfaces. The most common pigmented granular magnetic powders are:
They are typically used over non-porous light-colored surfaces. However, for darker textured surfaces, the white-gray powder can be used. 2. Magnetic Flake PowdersRather than rounded particles, they have a flakes structure. These flat, platelike particles are more efficient for fingermark development than the iron grit normally employed in commercial magnetic powders The first magnetic flake powder was developed by James et al, in 1991. They are usually available in lighter colors. Manufacturing Process: Magnetic flake powders are produced by milling spherical carbonyl iron with 3 to 5% of stearic acid in a suitable solvent to produce smooth-edged flakes. Their sizes usually range from 10 to 60μm. Surfaces: Mostly employed in the development of smooth and dark textured surfaces. 3. Magnetic Fluorescent Fingerprint PowdersThese magnetic powder fluorescence in the spectrum ranges from 450 nm to 570 nm. Commercially, they are available in red and green colors. The particles have granular geometry rather than flakes. Surfaces: For the development of fingermarks over multicolored plastic bags, glass, and non-porous smooth surfaces. 4. Thermoplastic PowdersThermoplastic powders are essentially photocopy toners that are used to visualize and develop fingermarks on paper tissues. It was first discussed for forensic purposes in 1967 by Jones RG in his research paper “Fused Fingerprints” without any magnetic component. But in 1982, Ball R. uses a modified mixture of iron-based magnetic photocopy toner with a magnetic brush for visualizing latent fingermarks. Read More:
What’s Inside a Magnetic Fingerprint Powder Kit?In a magnetic fingerprint powder kit, there are:
Please note: Magnetic Fingerprint Powder Kit is not much different than regular fingerprint development kit. Instead of only magnetic powders they also have non-magnetic powders and fingerprint brushes. Some fingerprint kits also have chemical developer liquids. How To Develop Latent Fingerprints Using Magnetic Powders?The following process should be followed for the enhancement and development of fingerprints using magnetic powders for forensic purposes: Step 1: Identify the Latent Fingerprints For DevelopmentUse alternative light to find the prints that need to be processed. Examiners should also add identifier tags on each item with fingermarks. Step 2: Photography Under Oblique LightingBefore beginning the development phase, photographs should be taken with oblique lighting (and alternate lighting). Each set of photographs should include at least two of the following:
Step 3: Application of Magna Brush on Magnetic PowderMagna brush (magnetic wand) has a small magnetic with a de-magnetized rod, which on pull/push releases the attached magnetic powder. A magnetic brush should be brought to the magnetic powder container that will attract powder and form a ‘brush’. Note: Magnetic powder on the brush should not be hung in the air as it tends to fall easily. Try to bring a magnetic container and Magna brush close to the impression. Step 4: Applying Magnetic Powder on Fingerprint SurfacesMagna brush with magnetic powder is applied to the surface, avoiding any direct contact of the magnetic applicator to the surface. Magnetic powder is the only part that should physically touch the surface. This minimizes the possibility of damaging the finger marks by scratches to the surface and degrading ridge details. Step 5: Re-Photography After Developing Finger impressionsOnce the development completes, the fingerprints should again be photographed. If the fluorescent magnetic powder is used, an alternative light source could be used for the development process. Photographs of ridge details contain:
Step 6: Lifting of Magnetic Powder ImpressionsLifting fingerprints should be avoided in case, the material can be transportable, or a semi-porous surface like paper (captures paper fibers too). Following are the lifting techniques that are both used at the laboratory as well as a crime scene investigation.
Before removing the lifting, sweep your finger across the tape and press out any air bubbles. Note: In case of lifting visible prints, avoid lifting them using lifters. This is because lifters work better to lift the powdered prints from the surface without visible fingerprint residue. If possible, after photographing, items should be packed for laboratory analysis. Step 7: Final PhotographyThe wrapup photography should include the casted material over the surface and along with prepared casted prints. In each step, take close-up photography of each element of the surface after removing the cast. Photographs of ridge details contain:
Step 8: Packaging of Developed FingermarksFollowing are the surface packaging considerations.
Can I Use Magnetic Fingerprint Powder Without Magnetic Brush?Yes, you can. If you don’t have a magnetic brush, such as a Magna Brush, you can definitely use a regular non-magnetic fingerprint brush. Animal-haired brushes with mop-style fiber mounts are the most frequent and best alternative for magnetic brushes with magnetic powder. For a smooth surface, you should use camel-haired brushes over squirrel fibers because they are less rough and allows you to get more details over smooth surfaces. However, in any case, magnetic brushes work better with magnetic powder. Advantages of Magnetic Fingerprint Powder
Disadvantages of Magnetic Fingerprint Powder
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What is the advantage of magnetic fingerprint powder?Our magnetic fingerprint powders are the best choice for the cleanest, least destructive method for powdering latent prints. With the Magnetic Fingerprint Powder, there's no risk of damaging or scratching latent prints because only the powder touches the print!
What is the magnetic powder?A mixture of iron and pigment particles, such powder is attracted by the magnet in the head of the magnetic brush, causing the iron particles to form a kind of brush.
What are the benefits and uses of magnetic and regular latent fingerprint powder?In general, magnetic powder is used on non-magnetic surfaces, and regular powder on iron-based surfaces. However, regular fingerprint powder is inappropriate for some surfaces, including many plastics and textured surfaces, where magnetic powder develops latent prints very well.
What is magnetic fingerprint powder made of?Fingerprint powder is composed of many different ingredients that can vary greatly depending on the formula used. Most black fingerprint powders contain rosin, black ferric oxide and lampblack. Many also contain inorganic chemicals such as lead, mercury, cadmium, copper, silicon, titanium and bismuth.
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