Indented writing, a very special type of evidence, is often overlooked. An Investigator may not even be aware of it. Along with indented writing, this equipment also can be used to recover dusty footwear impressions. In a drug case or a kidnapping case, a note pad with no writing visible on it is the only piece of evidence. Is there no writing at all? Oblique lighting may reveal some indented writing on the top sheet of paper, but it can be really hard to see. Attempts at photography may be less than successful. What can you do?
In another case, some papers and nothing at all on the others. It would be impossible to photograph these on extremely low contrast images of dust on patterned or light coloured papers. What can you do?
A solution to both of these problems involves using an Electrostatic Vacuum Box .
The Electrostatic Vacuum Box holds the paper down while film is placed on it and charged with electricity to visualise indented writing on documents. If indented writing is being sought, the document is placed on the Electrostatic Vacuum Box and covered with Type IW plastic film. Switch the vacuum pump on. Electricity is passed over the surface with the use of a corona unit. Special developing powder is applied with a fingerprint brush to the plastic film all over the document. The powder collects in the indentations with the excess being brushed away. The indented writing is now visible and can easily be photographed due to the high contrast between the black powder and the film. This film can be covered with an adhesive backed film to preserve the powder-developed image. The original document is not damaged or altered.
To recover footwear impressions in dust from paper items, place the paper with the footwear impressions on the Electrostatic vacuum box. Cover it with type SP film and switch on the vacuum pump. Charge it with electricity using the corona unit. The dust in the shape of the footwear image will now be on the clear plastic film. Because of the vacuum, there is no air gap between the plastic film and the evidence paper. Since the particles of dust do not have to jump over this air gap, the resulting image is sharper. This procedure is suggested for use on papers from a crime scene, even if no footwear impressions can be detected with the unaided eye. Excellent, high-contrast photographs of the footwear impressions can result. with the use of a black background and directed lighting.
Vacuum Plater – 35 x 39cm
100-metre Roll of Type IW Film
100-metre Roll of Type SP Film
75g Developing Powder
25 Sheets of Adhesive Film