I remember learning about historic methods to cool water down and decided to try my own version for really cheap. This works by evaporative cooling similar to the way swamp coolers work but in this case to cool water down. It requires very few parts and does a pretty decent job at keeping the water noticeably cooler then outside temperature! Its hot outside and some cold water would be nice so lets get right to it!

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Here is a complete list of Supplies & Tools you will need. They are not all the same supplies I used but should be similar or better replacements.

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Supplies

1. Clay Planter Pot – (It must be a non sealed clay pot. Often sold as terracotta pots. You want a larger one for this project.)
2. Small 8oz Water Bottles – (I ended up using one of these since it would fit inside the pot slightly sideways with the lid over the top of the pot.)

Tools

1. Ryobi Hot Glue Gun Mini – (This is the one I used the mini glue sticks seem to hold better then some of the normal ones. Requires a Ryobi 18v Battery and the glue sticks are sold separately, these gorilla glue sticks 74 count would be a good choice.)
2. Normal Glue Gun – (This Surebonder is the one I used to use before I got the Ryobi Glue Guns. If you want plenty of glue sticks for cheap check out this 90 pack which is what I used before the Ryobi mini.)
3. Optional: Indoor/Outdoor Thermometer – (I used one of these to see quickly the inside water temperature vs the outdoor temperature.)

First step is simple tape some parchment or wax paper to the bottom of the clay pot over the drainage hole. This is mostly so it doesn’t leak out all over the desk surface and glue the pot to the hobby mat. If you don’t have parchment paper just use some scrap paper or cardboard instead.

I don’t want it to leak all the water at once so I simply hot glued the drainage hole at the bottom of the clay pot. You could probably use another type of glue but hot glue is simple and dries quick.

My plan is to put an inner bottle of drinking water inside the clay pot which will be filled with non drinking water. This step is mostly so we can see what the temperature is doing inside the drinking water bottle vs outside temperature. In this case the thermometer screen will be wrong the top that says outdoor is really the water bottle temperature and the bottom that says indoor is the outside temperature.

My hot glue was still a little tacky but was dry enough so I poured in water which both instant dried the glue and got use ready to try it out. The last picture is it full of water with the glass jar I tested first. For the rest of the steps I moved it outside as it will leak some water naturally through the porous surface of the clay pot which we need for this to work.

I liked this water bottle size better and it was made of glass so I tried it out first. After the first 2 pictures as well I added a clock so you could see how much time passed between pictures. The picture of a damp paper towel is when I took a wet paper towel and tried dampening the outside of the clay pot to speed it up. It will eventually start letting water out the sides very slowly through its porous surface I just tried to speed it up a bit. Which it was hot enough it was practically dry again by the time I took a picture.

The glass bottle was too tall to work with a lid which makes a difference having so I switched to a small 8fl oz water bottle with the probe inserted inside and the lid partially tightened so the wire of the probe could still work. In normal use I would shut the lid all the way to keep the water completely separate.

Take the drip tray that is used for this pot and insert it into the top of the clay pot to function as a lid. This also keeps the small water bottle under the water so it gets more of the cooling effect. I then refilled it with water and let it run over the sides to dampen the outside as well. It is a rather hot day so it once again dried pretty quick.

The first day I did the project I checked the temperature a few times every few minutes, then every few hours. Near the end of the night the outside of the clay pot was finally damp which is what we want for this to work. I also refilled it a little bit one last time before the final check of the night at 7:37pm. I left it outside overnight.

I went out to check on it the next day at 9:36am which with the thermometer in the direct sun said it was 104 degrees Fahrenheit. Its actually a few degrees less when not in direct sunlight. I moved it into the shade after this. I then checked it every few hours.

I had the idea that surrounding the outside of the clay pot with some kind of damp towel would speed up the evaporative cooling effect. I took a few paper towels and folded them in half then wrapped it around the pot and refilled the water and let it spill out the sides to completely dampen the paper towels.

After the paper towel I noticed the water temperature was dropping by about .2 degrees every minute or so. This is partially also due to the fact the water I poured over it was cooler then the water in the pot. But it did continue to cool off every few minutes for awhile so it is the evaporative cooling effect as well. It became very overcast but it still continued to cool down the water. I refilled it one more time before I left it for over an hour. I wanted to test this for longer but I ran out of time, that being said it still worked to confirm the test, see the last step!

I came back outside after about an hour and a half and not only had the outside temperature gone up now its over 100.4 degrees Fahrenheit, and that's the temperature in the shade. There was a break in the clouds which I included a picture of. Even so the water had managed to cool with nothing but evaporative cooling all the way down to 76.9 degrees Fahrenheit! That's 23.5 degrees Fahrenheit less using nothing but evaporative cooling which is pretty impressive for just a clay pot and some damp paper towels. The color had changed on the paper towels in the time I was away likely due to this being a used clay pot that once had plants in them and I didn’t deep clean it. So the only thing left is to enjoy this naturally colder water on such a hot day and it was very refreshing. If you live somewhere that gets hot and don’t have electricity, have spotty electricity, are out camping, or just want a backup I highly recommend doing something like this as all you need is water!

Here are some upgrade ideas:

1. Get a bigger clay pot or jug that can hold more water then you could fit a larger water bottle inside.
2. You could cool beverages in an can, jar, or bottle as well using this method, as long as it fits under the water it will work! With a much bigger pot you could do full size bottles as well.
3. You could also get a clay jug and just fill it with drinking water and place it in the shade and the whole thing would be cooler and drinkable. I used an old used clay pot so I didn’t want to do this. Also if you are using non drinkable water for the cooling water you also wouldn’t want to do that.
4. I am betting putting a small solar powered fan that blows right across it would improve the evaporative cooling effect and make it work faster on less windy days. For me it was decently windy on day 2 so the effects were maximized.
5. The most simple historical one I saw was a clay jug they would attach to a rope and hang up suspended in the air in the shade so that's an option too then wind would get it from all sides. Such as a spanish botijo.

If you would like to support me in making these projects you can do so here.

Do you have any more suggestions? I will add good ones to this list and if there is enough demand I will possibly do some of these ideas in the future.