Demonstrate basic primary color mixing for any age group with sturdy, inexpensive mixing wands or bottles.
We’ve all seen the project where you put oil and water with blue food coloring in a bottle to make “waves.” Oil and water don’t mix, of course, so the oil sits on top of the water and makes an interesting effect. It’s fun to look at and for older children can spark a conversation about liquid density. For the younger ones, though, wouldn’t it be nice to have two primary colors in that bottle, which when mixed would make one of the secondary colors?
Such a product does exist, but the price is a bit steep for what you get. I’ve discovered a cheap DIY alternative that can just as effective and attractive as the commercial tubes. Assuming you already have some basic ingredients and a little bit of creativity, you can make a nice set of color mixing tubes for less than $10.
Materials Needed:
- Three clear, waterproof, sealable plastic containers. Make sure they’re sturdy! Possibilities include tall and slender water bottles, aquarium lift tubes sealed with rubber chair leg caps, clear plastic tubing used for packaging various items, etc. Be creative! I went to my local Dollar Tree and found “bubble wands,” clear capped tubes with a bubble wand and solution inside. Their handles are even the right colors. Perfect!
-Light-colored cooking oil. I used “Pure Wesson Vegetable Oil” just because it was the lightest oil I could find. Whatever you have on hand is probably fine.
- Food coloring (red, yellow, blue)
- Candle-making dye (red and yellow). It might be possible to use crayons instead.
- Glue gun, aquarium sealer, Gorilla Glue, or some other waterproof glue
- Rubbing alcohol (optional)
How to do it:
1. First build your tube, if necessary. Clean it with hot water and, if you want, rinse with rubbing alcohol. If it has two open ends, seal one up and make sure it’s secure. Use lots of waterproof glue. Use more than you think you need, especially if the “wand” will be used by the children (as opposed to just being a demonstration item).
2. Put a few shavings (about a teaspoon) of yellow candle dye into a microwave-safe cup, and pour in the vegetable oil. Microwave this on high for 15-20 seconds. Stir well and repeat until the dye is completely dissolved. Add more if you want a more intense color. Let cool. Repeat to make some red oil. You’ll need about twice as much yellow as red.
3. Now prepare some blue and red water.
4. This step takes experimentation to find the right proportions to make good colors. For me, here’s what worked:
Orange: 2/3 yellow oil, 1/3 red water
Green: 1/3 yellow oil, 2/3 blue water
Purple: 1/3 red oil, 2/3 blue water
5. Pour your colored oil into the tube with the water. Leave a small pocket of air at the top to make mixing easier. The color from the oil shouldn’t migrate into the water, since candle dye isn’t water-soluble. Cover the open end of the tube and give it a good shake. You should get a decent green. If not, you may need to experiment with the intensity of the colors. Tip: don’t try to put food coloring in after you put oil in; it’ll just sit in globules within the oil. Instead, pour off the oil first.
6. When you’re satisfied, securely glue on the cover. Use lots of glue. Trust me, I speak from experience. Colored oil is not easy to get out of a carpet.
Variations
- If you can find small tubes with caps, like Steve Spangler Science’s “Baby Soda Bottles,” you could have each child make their own. (Or use mini water bottles.) Just prepare the colored oils beforehand.
- Try placing small objects in the tubes to see how they move through the liquids. Glitter would also be an interesting addition.
- You could use a large soda bottle to make a class-sized demonstration model. I wouldn’t give this to the students, though. Again, I speak from experience.
- To show the principles of separation, try using a dark-colored oil with plain water.
- Although alcohol is sometimes used in place of water in similar projects, be warned – it will pick up the candle dye’s color.
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