No two people have identical fingerprints, even those of homozygous twins have small differences that make them unique. When an individual touches a glass or other hard surface, they leave footprints, and if you make an appropriate homemade powder, you can easily detect and examine them.
Steps
Part 1 of 3: Prepare the Powder to Take Fingerprints
Step 1. Gather the materials
You need cornstarch, a measuring cup, a lighter or matches, a candle, a ceramic bowl, a knife or brush, and a bowl to mix the ingredients. The latter can be made of glass, plastic or ceramic; however, you cannot replace the ceramic bowl with another container, as the process of making the powder could cause the glass to crack or melt the plastic.
If you think making homemade powder is too complicated, you can buy some at craft, hobby or online stores
Step 2. Use the candle and ceramic bowl to create soot
First, light the candle with the match or lighter and then place the bottom of the ceramic bowl over the flame; in this way, a layer of soot develops on the container. Move the bowl over the flame so that the entire surface of the bottom comes into contact with the fire.
- Wear an oven mitt or use a tea towel to protect your hand from the heat.
- Always be careful when working with open flames; children should only proceed under the close supervision of an adult.
Step 3. Scrape the soot out of the bowl
Hover it over the container to mix the ingredients and use a blunt knife or brush to loosen the soot particles. You need about 5g of powder; the more soot you can get, the more powder you can prepare.
- Repeat these steps as many times as you feel necessary.
- Scraping the soot creates a lot of mess and is a dirty job; if you want to avoid getting your fingers dirty, wear gloves and, for the same reason, protect the work surface with a cloth.
Step 4. Mix the soot with the cornstarch
Use a scale to weigh how much soot you have collected and then add an equal amount of starch; mix the two powders thoroughly with a whisk.
For example, if you got 50g of soot, you need 50g of cornstarch
Step 5. Store the mixture in an airtight container
Place it in a plastic food container with a lid; alternatively, use a sealable plastic bag. These containers are airtight and prevent moisture from affecting the dust.
Keep the dust on a shelf in an uncrowded area of the house, otherwise someone could bump into the container and dirty the room with soot
Part 2 of 3: Take Fingerprints
Step 1. Find a footprint
Look for some household items that have recently been handled and that have a smooth surface; the smoother it is, the easier it is to take fingerprints. If you want to practice this, you can leave your own footprints by touching a glass.
Do not try to lift them from soft, flexible surfaces, as a special chemical is required in these cases
Step 2. Sprinkle the impression with the powder
When you have located the trace you want to detect, cover it completely with some of the powder you have prepared. Then, gently brush off the excess dust using a brush; you should see a dark, well-defined fingerprint.
Blow lightly on the track to remove excess dust
Step 3. Use clear tape to lift the impression
Get some clear tape and cut out a small segment. Place the sticky side on the dust-covered impression and then slowly peel it off to detect the mark left by your fingers.
Before lifting the tape, smooth the surface to remove any wrinkles
Step 4. Show fingerprint
Attach the tape segment to a blank sheet of paper or a blank postcard; the contrast between the black powder and the white surface allows you to analyze the imprint more easily.
Part 3 of 3: Recognizing the Footprints
Step 1. "Card" your family
Ask each member to leave fingerprints and transfer them to a postcard or white paper, noting the name, date of birth and gender of the "owner".
You can limit yourself to cataloging a fingerprint or all ten if you wish. If you collect a sample for each finger, it will be easier to recognize which ones you will detect in the future
Step 2. Classify the footprints
They are generally categorized into three groups - arc, loop and spiral - based on the general arrangement of the lines that form the footprint. The arched ones resemble a small bump or waves, the noose footprints form a long thin arc, while the spiral ones resemble a circle surrounded by smaller lines. These classifications are important for identifying footprints.
- Make a note of the category to which each family member's fingerprints belong by writing it on the card itself.
- Footprints can be tilted to the right or left. If this is also the case, indicate on the card which direction the spiral, loop or arc is oriented.
Step 3. Compare all the fingerprints you find
When you come across a tactile trace in the house, compare it with those in the "file"; try to find the champion that matches by inclination and category.
Keep the ones you were able to identify by sticking them on the back of each family member's personal card; this way, it is easier to recognize the ones you will find in the future
Advice
- If you want to identify fingerprints on a black or other dark colored surface, prepare a white powder; mix 50 g of corn starch with 50 g of talc instead of soot.
- For your purpose you can also mix powdered graphite (available in the "keys and locks" department of most hardware stores) with talc or corn starch in equal parts.
