NCJ Number
136023
Journal
Journal of Forensic Sciences Volume: 37 Issue: 2 Dated: (March 1992) Pages: 542-555
Date Published
1992
Length
14 pages
Annotation
This article reports on a study of the variations between paint coating obtained from unshaken and shaken spray paint cans including the problem encountered in a real case.
Abstract
The paint involved in the real case and four additional spray paints were examined to study the effect of shaking or the lack of shaking on the characteristics of the obtained paint coating. Three conditions of shaking were examined: no shaking, slight shaking, and vigorous shaking. Reflectance microspectrophotometry of the paints was conducted using the Docuspec TM/1 (Nanometrics Inc.) system. A x20 objective was used to record spectra, and the measuring area was approximately 40 x 40 mm. Scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS) was carried out using a CamScam III scanning electron microscope combined with a Traco Northern TN5400 EDS system. Since transient phenomena were observed while spraying the unshaken spray paints, the paint coating characteristics of the spray of unshaken spray paints were examined as a function of time. From the test results, the study concludes that at the beginning of spraying unshaken spray paints, a high concentration of inorganic material comes out first, since it is in the bottom of the can where the tube is located. Following that, the solvent above the settled solids "cleans itself a way" into the tube by creating a crater around the end of the tube so that afterward mostly solvent comes out during the spraying. Results show that large variations occur in the characteristics of sprayed paint coatings, depending on whether or not the cans have been shaken prior to the spraying. 14 figures and 6 references