Separating Glitter with a Homemade Centrifuge

Make Your Centrifuge

In the first part of this science project, you will make your centrifuge using a salad spinner, adhesive putty, and rubber bands.

1. Take out two small sticks of adhesive putty, or an amount of adhesive putty that you think could easily cup the bottom of a 50 milliliter (mL) centrifuge tube.
2. Stretch the adhesive putty out and fold it over on itself.
3. Repeat step 2 until you have made a flat, roundish piece of adhesive putty that is a little larger than a silver dollar.
4. Mold the adhesive putty around the bottom of a 50 mL centrifuge tube, covering the cone part (up to about the mark that says "5"). It should look like Figure 2.
   1. Mold the putty fairly thickly around the tube.

Image Credit: Teisha Rowland, Science Buddies / Science Buddies
Figure 2. Mold the putty so that it fits in a thick layer around the very bottom of the 50 mL centrifuge tube.

5. Repeat steps 1-4 with a second tube.
6. Place the two tubes in the salad spinner basket as shown in Figure 3. Put each of the tubes on opposite sides of the basket and tilt them so that their tops meet in the center.
   1. Wedge and push the putty ends of the tubes into the bottom edge of the basket.
      1. Try to keep tubes in place by molding the putty to the basket a little.
   2. Do not worry if the tubes fall over. You will be securing them in place more firmly in the following steps.

Image Credit: Teisha Rowland, Science Buddies / Science Buddies
Figure 3. Tilt the two tubes so that their putty ends are wedged in the bottom edge of the basket and their tops meet in the center. The pictures show the tubes from two different angles in the basket.

7. Using two new tubes, repeat steps 1-6 so that you have a total of four tubes with putty on one end. Place the two new tubes in the basket as shown in Figure 4. Put the new tubes between the ones already in the salad spinner basket and tilt the new tubes so that their tops also meet in the center.
   1. Again, wedge and push the putty ends of the tubes down into the edge of the basket.
      1. Try to keep the tubes in place by molding the putty to the basket a little.
   2. Each tube should be about the same distance from the tube on its left or right.
   3. Do not worry if the tubes fall over. Just try to keep them roughly in place.

Image Credit: Teisha Rowland, Science Buddies / Science Buddies
Figure 4. Place four tubes with putty on their ends in the salad spinner basket so that each tube has its putty end wedged into the bottom edge of the basket and the tops of the tubes meet in the center. Keep all tubes equally spaced from each other. The pictures show the tubes in the basket from two different angles.

8. Place four small pieces of putty in between the tubes where they meet at the center of the basket, as shown in Figure 5.
   1. This will help keep the tubes in place when they are being spun.
   2. Try to adjust the tubes so that they are as centered as possible.
   3. Using thicker pieces of putty will work better.

Image Credit: Teisha Rowland, Science Buddies / Science Buddies
Figure 5. Place four small pieces of putty in between the tubes where they meet at the basket's center to help keep them in place. The pictures show the tubes in the basket from two different angles.

9. Once the tubes are centered and seem stable, put a rubber band tightly around the tops of the tubes, as shown in Figure 6. Put three or four rubber bands on the tubes in this way.
   1. This will help keep the tubes in place when they are being spun.
   2. Make sure the rubber bands are tight around the tops of the tubes.
   3. If you have larger rubber bands, fold the band on itself and put both loops around the tops of the tubes.

Image Credit: Teisha Rowland, Science Buddies / Science Buddies
Figure 6. Put three or four rubber bands around the tops of the tubes, as shown here with one rubber band (marked by the arrow). This will help keep the tubes in place. The pictures show the tubes in the basket from two different angles.

10. Place the basket in the salad spinner and put the lid on the spinner, making sure it fits over the tubes inside.
    1. If it does not quite fit, try slightly adjusting the positioning of the tubes to see if you can get the lid to fit.
    2. If you still cannot fit the lid on the salad spinner, you may need to use a larger salad spinner or a different style of salad spinner for this project. Note: See the Materials and Equipment list for details on the kind of salad spinner needed.
11. Set a timer for one minute or have a clock nearby.
12. Spin the salad spinner with the tubes inside the basket for one minute.
    1. Tip: Try holding the salad spinner flat on a counter with one hand while spinning the salad spinner with your other hand. You might want to ask an adult helper to hold the salad spinner in place.
    2. If the tubes do not stay in place, try any of the following:
       1. If it looks as if the tubes' tops are not centered and equally spaced from each other, try to adjust them.
       2. Add more putty between the tubes.
       3. Put another rubber band around the tubes' tops.
       4. If it is the putty ends that came loose, push the ends more into the edge of the basket, molding the putty into the basket.
    3. If the tubes stay in place, your salad spinner is ready to be used as a centrifuge.

Centrifuging Glitter

In this part of the science project, you will test your salad spinner centrifuge on glitter in liquid to see how well your centrifuge separates the glitter from the liquid. Specifically, you will compare how well your centrifuge separates the glitter from the liquid to how well gravity alone does this.

1. Remove the tubes from the centrifuge, one by one.
   1. Take off the rubber bands and remove all of the putty from each tube.
   2. If the putty gets wet, it may not work well anymore, so try to keep it dry.
2. To each of the four tubes, do the following:
   1. Add ¼ teaspoon (tsp.) of glitter.
      1. You should do this over a piece of paper so that it is easy to collect any glitter that does not make it into the tube!
   2. Add 10 mL of water.
      1. Use the markings on the tubes so you know how much 10 mL is. The mark near the bottom that says "10" is where you should stop pouring to get 10 mL.
      2. What does the glitter do when you add the water? Where does it end up in the tube?
   3. Add one drop of liquid dish detergent.
      1. The detergent should help prevent glitter from sticking to the tube or floating.
   4. Add 30 mL of light corn syrup.
      1. Again, use the markings on the tube so that you know when you have added enough light corn syrup.
      2. Because each tube already has 10 mL of liquid in it, adding 30 mL of liquid corn syrup should fill it with a total of 40 mL of liquid, so add the liquid corn syrup until each tube is filled up to the mark near the top that says "40."
      3. Why do you think you need to add corn syrup? In step 2b, you may have seen that the glitter quickly falls to the bottom of the tube when it is in water. Adding corn syrup makes the liquid more viscous, or thicker and less fluid, which causes the glitter to take longer to fall to the bottom of the tube. This is important because it will enable you to compare more easily how well the glitter separates from the liquid using the centrifuge compared to using gravity alone.
3. Wipe all four tubes down with a paper towel or rag.
   1. If liquid gets on the adhesive putty it can damage it and make it unusable in the centrifuge.
4. Using a permanent marker, label one tube #1, another tube #2, another #3, and the last #4.
5. Put the cups of putty on the bottom of each tube again. Make sure the putty is firmly attached to each tube.
6. Quickly flip each tube upside down and then right-side up again. (This is called inverting the tube.) Do this about 10 times for each tube or until the glitter is evenly mixed throughout each tube. Invert each tube the same number of times.
   1. If the glitter is not evenly mixed, invert the tubes a few more times until it is.
   2. Do this to all four tubes at the same time. You can try doing this by having two in each hand or by having an adult help you do this.
   3. Take a moment to look at how the glitter looks in the tubes, but do not take too long.
7. Arrange the tubes in the centrifuge, as shown in Figure 6 in the previous section.
   1. Set the centrifuge up with these tubes as you did in the section titled "Make Your Centrifuge," following steps 6-10, using the putty pieces you already molded and prepared.
8. Spin the tubes in the centrifuge for one minute.
   1. Do this as you did in the "Make Your Centrifuge" section in steps 11-12.
   2. Try to spin the centrifuge at a regular speed, as fast as you feel comfortable going, for most of the minute.
   3. When the minute is up, stop spinning the centrifuge and let the tubes slowly come to a stop (do not quickly stop the centrifuge from spinning; doing that might cause your samples to remix).
   4. Tip: If one of the tubes comes loose while you are spinning them, stop the timer and slowly stop the centrifuge. Try to figure out why the tube came loose and troubleshoot the problem by following step 12b in the previous section. After securing the tubes, continue the timer and resume spinning the tubes.
      1. If it looks like the sudden stop remixed some tubes but not others, repeat steps 6-8 (in this section) for all four tubes.
9. Carefully remove each tube from the centrifuge. Have an adult helper try to hold each tube at about the same angle as it was in the centrifuge. Remove the putty from the tubes. Look at each tube.
   1. Where is the glitter in each tube? Is it all on the bottom, or is some on the sides or still floating around in the middle of the tubes? If there is glitter on the side of the tube, which side is it, in relation to how the tube was angled in the centrifuge? Write your observations in your lab notebook.
      1. If there is some glitter on the side of the tube, why do you think this would be? Hint: Re-read the Introduction.
10. At the bottom of each tube, there should be a small clump of glitter. This clump can be thought of as a pellet. But not all of the glitter will be at the bottom. There will also probably be a lot of glitter in the rest of the tube, especially on the side of the tube. Using a permanent marker or dry erase marker, make a small mark straight across where the pellet, or clump, seems to end, such as shown in Figure 7, on the left side, with the arrow.
    1. Tip: If you are having trouble seeing where the pellet ends, try holding the tube up to a bright light. The pellet is the area at the bottom of the tube where the light does not shine through. You may need to roughly estimate where the pellet ends.
    2. If you do not seem to have a pellet at the bottom of your tubes, try repeating steps 5-9 again but this time have an adult spin the tubes faster.

Image Credit: Teisha Rowland, Science Buddies / Science Buddies
Figure 7. After spinning your tubes, use a permanent marker or dry erase marker to make a small mark where the pellet, or clump, ends in each tube. As an example, the arrow in the picture on the left shows where you would mark this tube. You may need to hold each tube up to a light to see where the pellet ends. In the picture on the left, you can see there is glitter along the left side of the tube. Why do you think this occurs? How do you think this tube was angled in the centrifuge? The picture on the right shows what this tube looks like after being marked and shaken again.

11. Take a picture of each tube using a digital camera.
    1. For each tube, take a few pictures of the whole tube and of the pellet at the bottom.
       1. Try to include the number of the tube in the pictures. If you do not, in your lab notebook, try to keep track of which pictures go with which tubes.
    2. If you are using colored glitter, try to take the pictures in front of a solid white background.
12. Set up four tall, clear drinking glasses.
13. Shake each tube as you did in step 6.
    1. The tubes should now look like the picture on the right in Figure 7.
14. Set each tube upright in a drinking glass.
    1. Do not worry if the tube is leaning in the glass a little. Arrange the tubes so that you can see the marks you made at the bottom of each tube.
15. Start a timer or write down what time it is in your lab notebook.
16. Watch the tubes in the glasses to see how long it takes the glitter to form a pellet at the bottom of the tube that goes up to the mark you made.
    1. This may take several minutes, so you will need to be patient! After a few minutes, once you see how slowly the glitter is falling, you can check on the tubes every five minutes. Just do not forget about them!
    2. While you are waiting, copy Table 1 into your lab notebook. You will be writing your data in this data table.
       1. Note: Part of the data table has already been filled in for you. Because you should always be spinning the centrifuge for one minute, you will record that it takes one minute for the glitter to settle when it is centrifuged.
       
       

       	Time for Glitter to Settle
       	Trial #1		Trial #2		Trial #3
       	Centrifuging	Gravity Alone	Centrifuging	Gravity Alone	Centrifuging	Gravity Alone
       Tube #1	1 minute		1 minute		1 minute
       Tube #2	1 minute		1 minute		1 minute
       Tube #3	1 minute		1 minute		1 minute
       Tube #4	1 minute		1 minute		1 minute
       Average	1 minute		1 minute		1 minute

       
       Table 1. In your lab notebook, make a data table like this one. You will be writing your data in it. Note: The centrifuging times have already been filled in for you. (Because, according to the Experimental Procedure, you should always spin the centrifuge for one minute, you will record that it takes one minute for the glitter to settle when centrifuged.)
       
       
    3. It may be hard to tell exactly when the glitter settles up to the pellet mark you made, so just do your best job at estimating when it reaches the mark.
       1. Tip: If you are having trouble seeing where the pellet ends, try holding the tube up to a bright light, but do not jostle or shake the tube. The pellet is the area at the bottom of the tube where the light does not shine through.
       2. You can compare how much glitter is settled in the tube to how much was settled in the picture you took right after centrifuging.
    4. When the glitter fills up to the pellet mark on a tube, check the timer or see what time it is. How long did it take the glitter to settle to the mark in that tube?
       1. Write this time in the data table in your lab notebook. Write it in the "Gravity Alone" column.
       2. Repeat this step for each tube.
    5. When the glitter has settled to the mark, make and record observations of each tube as you did in step 9 and take a picture of each tube as you did in step 11. How does the glitter in the tube look different from how it looked just after centrifuging?
17. Clean off the mark you made at the bottom of each tube.
    1. If you are using a dry erase marker, use a paper towel or rag to wipe the mark off.
    2. If you are using a permanent marker, have an adult help you put a dab of 70% isopropyl rubbing alcohol on a paper towel or rag and wipe the mark off with it.
18. Repeat steps 5-17 two more times. Each time, in step 16, record your times under a different trial number. You should do a total of three trials this way.
    1. Repeating an experiment three times is important to show that your results are accurate and reproducible.
19. Once you have completed the three trials, look at the data table in your lab notebook and analyze your results. How efficient is the centrifuge?
    1. Calculate the average time it took for the glitter to settle by gravity alone for each trial by adding up the time it took for each tube and then dividing this number by four. Write these answers in your data table in the row labeled "Average."
    2. Make a bar graph of the average time it took the glitter to settle in each trial. You will want to make one graph for each trial, so you should end up with three graphs total. On the y-axis (the vertical axis going up and down) put how long it took the glitter to settle and on the x-axis (the horizontal axis going across) label one bar "Centrifuging" and one bar "Gravity Alone." Do not forget to label each graph with the trial number.
       1. You can make a graph by hand or use a website like Create A Graph to make a graph on the computer and print it.
    3. Was using your centrifuge more efficient at making the glitter settle to the bottom of the tubes than using gravity alone, which you tested when you placed the tubes in the glasses?
       1. Hint: When you spun the tubes in the centrifuge, you spun them for one minute. How many minutes did it take the glitter to make the same-sized pellet when the tubes were placed in the glasses? Did it take a lot longer?
       2. What other differences did you notice about where the glitter was in the tubes after centrifuging them or letting them settle to make a same-sized pellet? Why do you think this happens?
          • You may want to include some of the pictures you took on your project display board! If you do, you may also want to take a picture of what the glitter in the tube looks like right after it has been shaken.
       3. Centrifuges used in laboratories spin even faster than the one you made for this project. If you spun your tubes in one of these centrifuges, what do you think the glitter would look like afterwards? Where would it be in the tube?