Development of Friction Ridges on Porous & Non-Porous Surfaces Flashcards
Definition of porous substances
Surfaces are absorbent, which means that they are permeable to gases or liquids
Ex. Porous surfaces include paper, cardboard, and unfinished woods
Definition of amino acid
Organic compounds that combine to form proteins
Factors that would cause porous substrate to go in deeper or not as deep
fingerprint residues do not penetrate into smoother (less-porous) papers as thoroughly as more porous papers.
How porous it is and enviornment)
They also found that deeper penetration of fingerprint residues results in higher quality processed prints.
What theme would leave the colour of ruhemann’s purple
Ninhydrin
What are the condition for processing something with
DFO
The DFO process must be completed in a dry environment
How do you dip the DFO print & process it?
DFO is applied in a fume hood by thoroughly saturating the porous substrate by dipping, spraying, or painting.
The item saturated with DFO is dried in a fume hood. It must then be heated in an incubator at 100°C for 20 min.
The resulting fluorescent prints are viewed with a laser or an alternate light source set to 530-570 nm (green light).
The items must be viewed through orange or red goggles and photographed with an orange or red barrier filter.
The attributes of a physical developer print?
Used when porous substrates have been wetted due to environment or humidity and reacts to water-soluble sebaceous components of latent print residue.
Signature: dark gray to black images due to the deposition of silver metal along the latent print ridges.
What does CA need to work?
vaporization and polymerization
Vaporization: the conversion of a liquid into a gas.
Polymerization: occurs when individual molecules (monomers) forma long chain known as a polymer. The monomers adhere to latent print residue
How does CA processing work?
The two most popular methods are the fuming chamber method and the vacuum chamber method Both methods cause the liquid CA to vaporize, so that the fumes can interact with the latent print residues.
In the CA fuming chamber, the liquid CA is heated until it vaporizes.
In the vacuum chamber, a pump pulls air from the chamber to reduce the pressure, resulting in the immediate vaporization of the CA without heat.
How to process print on fabric
(VMD)
Vacuum Metal Deposition
Acidity in perspiration- what does it do to a cartridge case
Perspiration is acidic and may cause latent prints to be etched on the cartridge surface without using any chemical development techniques
Duct Tape process
Process the non-sticky side first
Reagent’s such as amino black- what do those reagents react with?
All chemicals react with proteins in blood
