| Author | Message | ||
     Hannah |
Thank you so much for your help! I bought different powders for my project over the time period you took to answer. I bought a fluorescent powder, as well as a labled "Latent" type. I am testing these powders for most point matches to an original print. Should I be testing different powders? Whatt types should I use? What light can I use for fluorescent powders? If you could answer these questions it would be most appreciated. Hannah | ||
| Ernie Hamm |
Because there was no reply e-mail option provided for "Hannah", the holidays and no acknowledgement of receipt, I am re-posting this information one time in the hopes that Hannah gets her information. To Hannah: Sorry about a delay in getting information on powders to you, but the Paul Norkus the Webmaster wrote about was a very long time colleague (38 years) and so I was out of town for a few days. Powder processing for latent prints is the oldest form of latent development. Basically, a powder substance is applied to a surface with a soft brush (commonly called a Camel hair brush, but it is not really made with “Camel” hair). Latent print residue, which may be primarily natural body fats and oils, attract the powder and make the ridges visible. The preferred powder color is one with contrasts with the background, black for light surfaces and white for dark surfaces. There is also a Bi-Chromatic powder that has properties of both black and gray powders and which appears black on light surfaces and light on black surfaces. Magnetic powders are powders that have been mixed with a ferrous product as a ‘carrier’ and the mixture is then attracted to a magnetic wand. The resulting collection of powder at the end of the specially designed wand forms the “brush”. The magnetic wand method can be less destructive than the Camel hair brush method, which may be more abrasive when passed over a hard surface. The magnetic powder can also be ‘cleaned up’ and returned to its container for use another day. Fluorescent powders are simply powder substances that fluoresce under Ultra-Violet lighting or other alternate light forms. These make the powders more useful on multi-colored surfaces when ridge lines will run across a myriad of colors and the examiner is able to see the entire fluorescing print. Fluorescent powders can be magnetic or non-magnetic. It should be noted that powder processing by any means is normally used only on non-porous surfaces. On porous surfaces, the latent residue can be absorbed into the material and chemical substances will react more favorable than powders. Powders are only really effective when the residue is laying on the hard surface. There can be exceptions, but this is up to the discretion of the individual examiner. A little basic, but I hope it answers some questions. Best of luck in your endeavors. | ||
| Hannah Sloss |
I am trying to understand the fundamentals of the fingerprint dusting method for a science project. I would like to know if there are different types of powder I could do a comparison of for my project. I have heard of black powder, and am confused if there is a difference between magnetic powder and fluorescent powder. I would really appreciate it if someone could please answer my question, for I have been searching for a long time...Thanks. Hannah Student |
