Wednesday March 10th, 2010

SVN 3M
1. Begin Silver Nitrate print development.
A) Place a print on a piece of paper using any finger. You can also try placing a print on a piece of untreated wood. (Silver nitrate reacts with the chloride ions in the salt in your sweat, so - you should try to have a sweaty fingertip for this. Make a fist for a minute or do some jumping jacks and then touch your forehead). Wait for a minute to be sure the print is dry.
B) Spray silver nitrate onto the paper. This will react with the chloride to make silver chloride (white)
C) Wait 15 minutes or until the paper looks dry.
D) Expose the paper to bright light. UV light will break down the silver chloride into elemental silver which will appear greyish, and hopefully make the latent print visible.
E) Dip the print in distilled water. This should stop the paper from overexposing.
F) Give the print to a partner and see if they can determine which finger you used (using your data card from "Analyze Those Prints"

2. (During the waiting times of the silver nitrate activity): Fingerprint Ppoint Lesson - Silver Nitrate method, Ninhydrin method, Gentian Violet. Make sure you know which component of sweat each developing technique targets.

Test this Friday.