What can we smell? In order to smell something, it must have two properties. The first is that it must be in the air so that it can get into your nose. Most things you smell have liquid particles that can be carried into the air, and this is why many smelly products are liquids (e.g. perfumes, air fresheners, etc.) The second requirement for something to be smelled is that the tiny particles now in your nose must fit the receptors (little detectors that are specific for different molecules in the air). This works because most smells are really made up of primary odors that your nose can split up and identify. All of the possible smells happen by mixing these smells in different combinations and amounts.
Scientists were able to determine the 4 major taste components and map them directly to areas on the tongue, but efforts to do the same with smells have proved more difficult! For this reason, categorizing smells may require you to use more than the primary odors (especially since most of these smell BAD!) Shown below is a list of possible smell descriptors. If you do not know exactly which category something fits in, make up your own!
Scented inserts are used to sell perfume and can be found in magazines and
department stores. They are usually folded pieces of paper that has a kind of glue holding
it closed. When you unfold it, the glue pulls apart and releases the fragrance. This works
because the microcapsules are broken when you pull apart the paper (physical rupture of
the outer layer) releasing the active ingredient (the smell) into the air. Scratch-and-sniff
stickers work in a similar way (see Scratch-and-Sniff Stickers activity).
Making a scented insert is harder than it may seem. The adhesive (glue) used to
hold it closed cannot have smell of its own, as this would interfere with the perfume
smell. Also, some glues will react with the perfume to make it smell different. The most
important thing is for the smell to stay the same for as long as possible. Researchers test
and compare many possible combinations of scent and adhesive ingredients to reach this
• Learn to categorize different scents
• Test different adhesives for your insert to see which holds smells the longest
• Compare different scented products (main scent, ingredients, etc.) to see which
lasts the longest.
Materials needed (for testing two
products – you may want to test more!)
• 1 piece of Unlined Paper
• Scotch Tape
• Glue Stick
• 2 scented products to test (things
like perfumes, body wash,
shampoo, conditioner, and other
scented hair products) **
**NOTE: You may want to read the
first half of the “Comparing Scented Inserts” activity (through part A) BEFORE choosing
your samples. This will help you to set up a good experiment!
Activity (Estimated time for making samplers,1 hour)
In this activity, you will be the researcher and try to determine which scents and
adhesives make the best scented insert!
A. Cutting and Labeling Your Scent Samplers.
1. Cut one piece of paper into four equal pieces. Fold
each over, leaving ~2cm hanging out on the bottom.
Divide folded pieces into pairs.
2. For only 1 of each pair, cut the top (part of the
fold) only into four even strips (see picture to right.)
Label these two as “glue sample”, and label the two
uncut pieces as “tape sample.”
3. On the bottom of all your sheets (glue and tape samples), label each section (of the
four), as tomorrow, 3 days, 5 days and 1 week. (see Figure 1, next page).
4. On the top of each tape sample, assign a letter to the sample, and place the SAME
letter on the glue sample paired with it. Also, write the date on the top sheet. Have your
two scented products ready.
5. On the top sheet of the tape sample, write the primary use of your first scented
product (e.g. body spray, conditioner, etc.), the name of the scent on the bottle, the first
three ingredients (look on the bottle, may not be given.)
Overlap of bottom sheet
(divided into four sections) Top sheet
Label overlap as:
Figure 1. Example of Labeled Tape Sample. Glue sample will ONLY have bottom sheet
labels (because top sheet will be cut and glued.)
6. Smell the sample (assigned to this letter) and attempt to identify the strong smells in
the scent using the previously mentioned “odor identifiers.” Write these down (labeled
“Strong Smells” in Figure 1) in order beginning with the strongest and progressing to the
weakest one you can smell - try to get at least three per scent!
[Tip: If you have trouble smelling a product (your nose gets tired), take a deep whiff of
something relatively unscented like your shirt sleeve, a clean towel, etc. This should
refresh your nose for more smelling! ]
Tape Sample A
1. Alcohol (denat.)
7. Repeat for your other sample.
B. Making Your Scented Samplers
Now, make your scented samplers (one glue and one tape sample per scent).
1. For each glue sample: Get some of the scent on a
Q-tip and gently rub a small line on the bottom sheet in
each section, try to use the same amount for each
2. Now we must cover the scented lines! Apply glue
stick to the underside each strip (the cut side) labeled
tomorrow, 3 days, 5 days and 1 week. Fold over and
press the glued side to the paper against the scented
line, starting from the bottom (1 week) and proceeding
upwards to the other strips.
3. For each tape sample: Apply scents to the paper as you did for the glue samples, but
make sure that the area is small enough to be covered by the tape.
4. Again we must cover the scented lines, but this time with tape instead of glued paper.
Get four pieces of tape by cutting a piece that is as long as the folded paper is wide. Fold
the left end of each piece to create a 1-2 cm tab (that isn’t sticky.) Use this strip to cover
the scent on one of the four sections. Repeat until all four sections are covered.
5. Save samples for use in the Comparing Scented Inserts activity.
1. How we smell: http://www.chemistry.wustl.edu/~edudev/Smell/smell.html
2. Primary Odors: http://food.oregonstate.edu/sensory/nancy7.html