CHEMICAL LIFTING OF PRINTS Name ______Pr ___

YOU MAY DO THESE LIFTS IN ANY ORDER, but look at the side notes concerning timing. PAY ATTENTION TO ANY VERBAL DIRECTIONS GIVEN BEFORE AND DURING TESTING! WEAR GLOVES WHEN WORKING WITH THE CHEMICALS.

THE FIRST TWO ACTIVITIES MUST BE DONE IN THE FUME HOOD IN THE RESEARCH LAB.

Ninhydrin 6% - reacts with amino acids in the perspiration from your skin to produce a purple reaction product called “Rhuemann’s Purple.”

  1. Write your name and period on the top of two strips of card stock that you have cut to the same size as a glass slide.
  2. Make a good fingerprint on each strip on the same side as your name and period. You will save one strip for silver nitrate staining later. Remember, we want SWEAT here. Wipe your fingers on a sweaty part of your body.
  3. Put on gloves.
  4. Place your strip in the fume hood.
  5. Hold the Ninhydrin Spary upright 6-10 inches from your card. Gently spary your strip until it is damp. NOTE: THE CAN HAS TO LAST FOR 60 STUDENTS. DON’T WASTE IT!

CAUTION: Ninhydrin reacts with amino acids. If you get any on your skin, your skin will turn color! It is NOT good for you! Be careful!

  1. Clip your strip to a clothespin and allow it to dry in the fume hood for 24 hours.
  2. If the print does not develop, expose the strip to the fumes from ammonia as follows:

·  Put on a pair of gloves.

·  Open a bottle of concentrated ammonia under the fume hood.

·  Hold the strip with the print over the bottle of ammonia, print surface toward the bottle.

·  Scotch tape this strip to the “Chemical Lifting” page. You may want to put a piece of packing tape over it to protect the print.

·  Fill in the listed information, including the print class.

Iodine Crystals – fumes react with oils and fatty deposits to produce a temporary yellow-brown reaction product.

a.  Write you name and period on the top of a strip of card stock that you have cut to the same size as a glass slide.

b.  Place a print on the strip on the same side as your name. You want this print to be oily, so make sure your finger has oil on it from, say, behind your ear.

c.  Put on a pair of gloves.

d.  Go to the fume hood and find a coplin jar containing some iodine crystals. YOU DO NOT WANT TO LEAVE THE LID OFF THE JAR FOR ANY LONGER THAN YOU HAVE TO, SO WORK VERY QUICKLY.

e.  Quickly take the jar lid off, slide the strip into the jar using the slots as a guide, and quickly put the lid back on the jar.

f.  Allow the strip to come in contact with the iodine fumes for three to thirty minutes or longer. You will know your strip has developed when the print has turned brown.

g.  Once you see the developed print, quickly remove the strip, being sure to replace the lid as quickly as you can.

  1. Immediately show me your print and have me initial it. This stain often fades fairly rapidly.
  2. Scotch tape your strip to the “Chemical Lifting” page.
  3. Fill in the listed information, including the print class.

Silver Nitrate (AgNO3) – After the moisture from perspiration in a latent print has evaporated, sodium chloride salts are left behind. The silver in silver nitrate will react with the chloride ion of the salt to form silver chloride, which is black or reddish brown when viewed with UV light.

  1. Make a “sweaty” fingerprint strip and let it dry.
  2. Put on a pair of gloves.
  3. SILVER NITRATE IS VERY EXPENSIVE. USE AS LITTLE AS NECESSARY. Using a clean Q-tip, dab a small amount of silver nitrate over your fingerprint.
  4. Place the print under a UV light and let it sit until it develops.
  5. Observe the print and call me over to see it.
  6. Scotch tape this strip to the “Chemical Lifting” page. You may want to put a piece of packing tape over it to protect the print.
  7. Fill in the listed information, including the print class.

Cyanoacrylate (Super Glue) – fumes react with (probably) body oils to form a solid white substance.

  1. Obtain a piece of plastic. Make a good, oily print on it. Label your piece of plastic with a black Sharpie.
  2. Tape it to the inside of the fuming chamber with a piece of scotch tape. Be sure the print is facing the chamber, not the glass.
  3. When everyone has put their plastic in the fuming chamber, we will set it outside and do the following:

1)  Put a bowl of water in the chamber to keep the humidity high.

2)  Put 10-20 drops of Super Glue in a foil boat and set that foil boat on a mug warmer.

3)  Turn the mug warmer on for about 15 minutes, or until the prints develop.

  1. Recover your print from the fuming chamber.
  2. Scotch tape this plastic to the “Chemical Lifting” page. You may want to put a piece of packing tape over it to protect the print.
  3. Fill in the listed information, including the print class.

Crystal Violet (Gentian Violet) – stains latent prints on the sticky side of tape. The latent prints on the sticky-side are from skin cells. (Latent prints left on the smooth side are made by oils and salts left on the tape.)These skin cells react with crystal violet to form a purple residue on the tape.

a.  Tear off a piece of duct tape just as wide as your finger that you are going to print and about 4 inches long.

b.  Press a finger onto the sticky side of the tape and then pull it off (hopefully leaving a few epithelial cells behind).

c.  Using forceps, dip the tape into a gentian violet solution and pull it right back out.

d.  Rinse with water and carefully blot off excess water.

e.  Place the tape, sticky-side-up where the print is, on a piece of paper towel to dry. Be sure you put your name on the towel!

  1. When dry (the next day), tape it to the “Chemical Lifting” page. Cover the tape with packing tape to keep your page from sticking to other papers.
  2. Fill in the listed information for the print, including the print class.