Tea Time: Science Fair

Jamie K, Clarke 6th Period, 1-22-15


In most countries in the world, tea is a part of their culture. They have native teas such as green, black, herbal, and oolong that are indigenous to their region. In today’s world, teas are still wanted during traditional ‘tea times’ but the large amounts of caffeine is not desired; thus creating decaffeinated tea. But are decaffeinated teas really decaf? In this lab, the amount of caffeine actually in decaffeinated tea will be tested by extracting it from decaffeinated tea using a tannic acid solution.

Caffeine is a odorless bitter crystal solid that is a stimulant.

Tea is a beverage created by pouring boiling water over dry processed tea leaves.Tannic acid is also called tannin. This is a group of chemical substances found in tree bark. Tannin is a thick reddish brown liquid which can be dried into a hard cake. Tannic acid is a mordant, and can pull certain amounts of caffeine out of foods.There are many different theories of decaffeinated tea. The most talked about one is using methyl xanthines, a series of compounds such as caffeine, theophylline, and theobromine. These compounds draw each other out when combined with Methylene Chloride, a chemical that draws compounds out of solutions such as water and tea, this creates a solution and when extracted by heat this exposes the caffeine in milligrams in its true crystal form.

Parts of the Expirement


The purpose of this experiment is to determine whether decaffeinated tea is actually decaf.


If there is caffeine in the decaffeinated teas, then there is no such thing as decaffeinated teas because the amounts of caffeine naturally inside tea leaves cannot be extracted.


Independent: Type of tea

Dependent: Amount of caffeine in tea

Controlled: Caffeinated Tea

Experimental Control Group: Decaffeinated and Caffeinated tea

Constant: Tannic Acid Solution


25 Tea bags of caffeinated black, green, and herbal teas.

Tannic acid

25 tea bags of decaffeinated black, green, and herbal teas

Distilled water

Graduated Cylinder

10 tea cups



Rubbing alcohol

Masking tape

Medicine dropper

Permanent marker

10 Test tubes


Label tea cup and test tubes for each type of tea. The labels should be caffeinated green tea, caffeinated black tea, caffeinated herbal tea, decaffeinated green tea, decaffeinated black tea and decaffeinated herbal tea.

2. Open 10 tea bags, 1 of each type , and place the tea bags in each corresponding cup.

3. Bring distilled water placed in a teapot to a rolling boil and pour it over the teas.

4. Allow the teas to steep for one minute.

5. Carefully pour 2 ml of each tea infusion into each corresponding test tube and allow the tea infusions to cool.

6. Dissolve 1 g of tannic acid in 1 ml of rubbing alcohol, then dilute the solution with distilled water to 10 ml. Be sure to make this as fresh as possible. Do not make this solution ahead of time.

7. Using a medicine dropper, add the tannic acid solution into 1 of the caffeinated tea cups, counting the drops added until a white substance is revealed. If an excess amount of tannic acid is added, the substance will disappear.

8. Record the number of drops added until the caffeine was detected.

9. Using a medicine dropper add tannic acid to a test tube of a decaffeinated tea, counting the drops added to see if it will draw out a white precipitate. Stop immediately when or if a white precipitate is seen. If a white precipitate is not found in the 40th drop, there is no caffeine present in the tea sample.

10. Record the results in a table.

11. Repeat steps 1-10 for the remaining samples of tea in the test group. Record data. Then repeat the entire procedures for the remaining amounts of tea bags, this should be 10 more test groups.


Averages of teas in drops

Black Caffeinated


Black Decaffeinated


Green Caffeinated


Green Decaffeinated


Herbal Caffeinated


Herbal Decaffeinated



Claim: Caffeine is in the decaffeinated teas,meaning there is no such thing as decaffeinated teas because the amounts of caffeine naturally inside tea leaves cannot be extracted.

Evidence: This can be shown in the study of decaf black tea. The pattern of black tea, which averages to 21.6, shows that there is caffeine in the tea consistently. When judging the caffeine amount in Green tea, it is a proven fact that decaffeinated green tea contains less caffeine than the other teas because the number of Tannic Acid solution drops was highest, an average of 35.04, this shows that is was hardest to extract the caffeine making it the least caffeinated out of the three caffeine free teas. The most caffeinated tea was Herbal because it had the lowest average of 12.04.

Reason: In herbal tea, there is a lot of caffeine found as it took the least amount of drops to find the caffeine. This can be reasoned by the different caffeine reduction processes do not take all traces of caffeine out of the teas. There is indeed, caffeine in decaffeinated tea. When the Tannic Acid solution was added to each type of tea, a white substance was present; showing caffeine inside the decaffeinated tea. As both types of teas were tested, the caffeinated and the decaffeinated teas, the consistency of present caffeine was in a close range of itself, making it dependable to form the conclusion there is no such thing as caffeine free tea, only caffeine reduced tea.


My hypothesis of If there is caffeine in the decaffeinated teas, then there is no such thing as decaffeinated teas because the amounts of caffeine naturally inside tea leaves cannot be extracted, was correct proving decaffeinated tea is not really decaf. This shows that decaffeinated tea is not really decaf, rather containing reduced caffeine tea. In this lab I have learned that caffeine is not able to be completely taken out of a natural source of the chemical. Even though decaffeinated tea contains a significantly less amount of caffeine, it still contains caffeine.

Sources of Error

In this lab, the data is not reliable because the tannic acid solution did not react to the alcohol to form the solution correctly. After having to add more tannic powder, the solution began to react to hidden caffeine in the tea. The data also only varies for the specific brands of tea and non-authentic machine based tea. It does not account for all types of tea and decaffeination processes.


This lab is important because it shows the amounts of caffeine that are found in tea, a popular beverage. In general, you can conclude that decaffeinated tea does contains caffeine, but in small amounts. This data can be used to inform individuals about the amount of caffeine that is going into their bodies without them knowing.


In this lab, I could have differentiated the types of tea further, and I could have calculated the exact amount of caffeine that is in the tea. This would have made a more reliable lab with better results and more stable results. There could have been the added variable of bagged v.s unbagged tea which made a contrast of caffeine and extra chemicals on the tea.

Works Cited

Barry, Roger D.

"Tannic acid." World Book Advanced. World Book, 2014.

Bayer, Barbara M.

"Caffeine." World Book Advanced.

World Book, 2014.Web. 6 Oct. 2014.

"Decaffeination 101: Four Ways to Decaffeinate Coffee." Coffee Confidential RSS. N.p., n.d. Web. 6 Oct. 2014. <http://www.coffeeconfidential.org/health/decaffeination/>.

Lamba, Savi.

"Tea." World Book Advanced. World Book, 2014.

Web. 6 Oct. 2014.

"Tea and Theophylline." Helios.hampshire. N.p., n.d. Web. 2 Oct. 2014. <http://helios.hampshire.edu/~nlNS/mompdfs/TeaTheoph.pdf>.

Decaffeination 101: Four Ways to Decaffeinate Coffee. (n.d.). Coffee Confidential RSS. Retrieved September 30, 2014, from http://www.coffeeconfidential.org/health/decaffeination

Tea and Theophylline. (n.d.). helios.hampshire. Retrieved September 27, 2014, from http://helios.hampshire.edu/~nlNS/mompdfs/TeaTheoph.pdf

"Which Decaffeinated Tea Type Contains the Least Amount of Caffeine?" Which Decaffeinated Tea Type Contains the Least Amount of Caffeine? Web. 2 Jan. 2015.