PBS KidsZOOM Home Back to Activity
Science Rocks!

Solar Still


your results

Sent in by:
Mammy of Los Angeles, CA

Can you survive on just saltwater and sun?

Materials Needed

  • large bowl
  • short glass or cup
  • tape
  • plastic wrap
  • small rock
  • pitcher of water
  • salt
  • long spoon for stirring



  1. Check with a grown-up before you get started.
  2. On a deserted island, there's ocean water all around you - but you can't drink any because it's too salty. Here's how to turn saltwater into fresh water using the sun (and gravity.)
  3. First make saltwater by adding salt to fresh water. Stir the water until the salt dissolves.
  4. Now pour about two inches of saltwater in a large bowl.
  5. Take an empty glass and put it in the bowl. The top of the glass should be shorter than the top of the bowl, but higher than the saltwater.
  6. Put plastic wrap over the top of the bowl. You may need to use tape to make sure the seal is tight.
  7. The last step is to put something heavy right in the center of the plastic wrap, over the empty glass. That will weigh the plastic down and help you collect the water. Now you've made a solar still. It's called a still because it distills, or purifies, water.
  8. Leave your still outside in the sun. Leave it alone for a few hours, or even a whole day. The longer you leave it out, the more water you'll collect.
  9. When you're ready to check your still, take the plastic wrap off and look at the water that's collected in the cup. Do you think it's salty or fresh? Taste it, or use a saltwater tester to find out!

Ready for the sci scoop on how distillation works? Rays from the sun heat up the salty water in the bowl. When the water gets warm, it evaporates and becomes a gas. When the gas rises and hits the plastic wrap, it turns back into water droplets. Eventually, gravity makes the water droplets roll down the plastic wrap towards the rock. Then the water droplets slide off the plastic wrap into the glass. The salt doesn't evaporate, so it gets left behind in the bowl. Water evaporates in the same way from lakes, rivers, and oceans. The water heats up, turns into a gas, and then condenses to fall back down as rain.

See if you can distill fresh water from other liquids like cola, orange juice or even applesauce. Test it out, and send your results to ZOOM!

You can also send us your pictures or video of this ZOOMsci:
Box 350
Boston, MA 02134

Some of your Results

Jason, age 11 of Brooklyn, NY wrote:
It made an annoying buzzing sound, but it was so cool. Even my teacher, Mr. P, was amazed.

Samantha, age 10 of Manhattan, NY wrote:
The different liquids I tried made this buzzing sound but either way it was awesome. When I tried it, it was da bomb. I tried different things like saltwater/borehole water as I like to call it.

Destany & Ivonne of Richmond, TX wrote:
i think this project was really good cause me and my friend ivonne did it and it turned out to be fabulous!!!

Cece, age 12 of Cleveland, OH wrote:
it was fresh and shiny.

ZOOM Fan, age 13 of DE wrote:
it worked sooo well!!!

Kerny, age 13 of Zeperhills, FL wrote:
The water turned fresh. It took like five hours it was cool.

ZOOM Fan, age 10 of New York, NY wrote:
It worked like magic. I put it outside for 7 hours and it worked.

Cleo, age 11 of Minneapolis, MN wrote:
It worked like a charm. it turned into fresh water.

Michelle, age 10 of Tracy, CA wrote:
water got in the cup and I used it as a science project for the science fair and got 2nd place.

Sabrina, age 12 of Albuquerque, NM wrote:
It didn't work I tried it 2 times

Kelsey, age 9 of Beaver Creek, OH wrote:
it filtered the water

Cassia, age 11 of Quesnel, BC wrote:
This worked fabulously! And I used it for my 6th grade science fair project combined with them Salt Water Tester and me and my partner Courtney made it with our projects to the regionals!!! Im so happy!

Ezra, age 8 of San Antonio wrote:
when I did the experiment it was very fun

Levi, age 11 of Pendleton, OR wrote:
It wouldn't work. I did the test 6 times and it doesn't work!

Eilaf, age 11 of Karachi, Pakistan wrote:
it was to cool and interesting. When I did it it really works

Ajla, age 11 of Walled Lake, MI wrote:
The salt piled every where under and at the bottom of the water.

Karen, age 10 of Torrance, CA wrote:
this happened because water evaporates and salt doesnt so its left behind!..

Nicole, age 14 of Jackson, MS wrote:
it tasty like saltwater

Mariam, age 11 of Houston, TX wrote:
i did this for a science experiment but it turned out to take forever! I had to use styrofome glasses but they floated so I taped them down. I did it with dirt water, tap water, rain water, and salt water. the bowls were exactly alike but I only go a drop of clear water

Kiera, age 15 of Baton Rouge, LA wrote:
IT was so awsome it work better than thought it was.

Sydney, age 13 of Sumter, SC wrote:
When I tried this, it did not work. The water evaporated and collected in the glass but it still tasted salty. It was pretty cool outside so maybe that's why but I still don't recommend this.

Ankanaa, age 10 of Calgary, SD wrote:
It worked out!!! Thanks to Zoom I found out a way to help the environment!

Kiki, age 12 of Norton, MA wrote:
I left my expieriment out for 8 hours and my glass was full.

Abbey, age 13 of Oshawa, ON wrote:
It didn't work well. My glass bowl took 3 days to collect water.

James, age 12 of Seneca, SC wrote:
The hypothesis of this science project is that a glass bowl makes a better solar still than a plastic bowl or a metal bowl. If I set three different kinds of solar still bowls out (plastic, metal, and glass) then the glass bowl will produce more clean water. Results: The first time I tried the experiment, distilling water using solar energy, it rained and I thought the bowls would be fine. The next day I went out and all sorts of debris had gotten into the water. So the next time it rained I rushed out there with the tarp and threw it over the experiments. The experiments were located on the picnic table. I measured the water three times in this experiment. The results of this project were that the metal bowl produced the most water, and the plastic bowl had the second most amount, the glass bowl did not work as well as I thought it would. Summary: This project was fun. I learned that the glass bowl did not produce the most water. I learned that the bowls did not produce that much water in a day, to take a measurement of the water. At first I thought there was lots of water in the cup. But after I checked it there were only a couple drops in the cup. Conclusion: If I could correct any problems I would try to make a waterproof solar still. I do not know how I would do this. I thought that the glass bowl would work the best because it collected more sunlight. But it seems that I was wrong. The metal bowl collected the most water. I would like to learn how really big solar stills operate.

Amanda, age 8 of Las Vegas, NV wrote:
When we went out to check our solor still it was filled with water, about 2" or 3". And the water was kind of a mix of both.

Tanya, age 10 of St. Anthony, ID wrote:
My teacher and I once tried solar still. and the salt water actually turned to fresh water. It was so cool!

Kaushik, age 9 of Fremont, CA wrote:
The process was cool. It made 1 oz. of the water inside the cup for me.

not yet implemented