[EDsteve]

Hello dear forum,

to be honest i am a electronic guy and my chemical skills aren't even enough to know in which sub forum my question should be in.

I am not sure for what to google. So maybe my question is answered already a 1000 times. Please be nice to me

Problem:
I am building a floating peer from empty water bottles. But as deeper the bottles go into the water as more compressed they get and loose buoyancy. Also waves will compress them in time as well nobody wants to hear the crackle sound when they deform all the time.

Solution:
Put pressure inside the bottles. I thought about several methods already:
1. before closing the bottles, put them in ice cold water for a few seconds. Result: works great, but i prefer to have higher pressure inside.
2. Put a small portion dry ice inside. Result: Would be perfect i guess. But I live on Sumatra in the jungle. Dry ice is way to far away.
3. Let a small fire cracker explode inside after the cap is closed. -> Still looking for firecrackers to try it. Sounds funny. But can work right?

Now i started thinking about baking soda and vinegar or any other house hold ingredient. Fermentation? But my knowledge is almost zero about these things. There will be thousands of bottles. So it should not be too expensive. And of course efficient. So a small amount should lead to a big volume of gas.

I should get most common chemicals cheap online. Sooo. Give me something to try and i will do

Regards
ED

[billnotgatez]

I am seeing visions of exploding or imploding bottles.
Scary to me.
Setting aside how workable this idea is.
What is the stress level of these bottles and how are you going to be sure you do not exceed it.
 

[EDsteve]

I will start small and add more if pressure not enough. So i can be almost be certain not to exceed the limit. When pressure high enough i know the right amount of the "ingredient" to put inside and the mass production can begin
And of course testing must be done behind a wall.

A soda bottle can hold minimum 150PSI or 10 Bar. There are many youtube videos out there who demonstrate that. I just made a quick test and jumped a few times on one of the bottles i have (not Soda). But they seems strong enough too. No crack.

Two Bar should be enough for my project.

Any idea?

[Borek]

What is the stress level of these bottles and how are you going to be sure you do not exceed it.

Carbonated drinks go up to 50 psi, quite a pressure.

[EDsteve]

Yes. They do. Coca Cola bottles for example are tested to withstand 150 PSI. And the stronger ones even 250PSI.

Is my question so difficult?

[billnotgatez]

Just now thinking about it and also wanting to make it safe and ease to do.
These come to mind

Baking Soda and Vinegar Chemical Reaction
https://www.youtube.com/watch?v=nRMyMIy7U6E
The classic elephant's toothpaste
http://www.periodicvideos.com/videos/elephants_toothpaste.htm
without the soap and color

This was from a quick search on GOOGLE
What do you think

[EDsteve]

Yeah. I tried the baking soda some days ago. But the volume expansion is way to small. I have a few thousand bottles here. So i can't use 200ml vinnegar and 2 big spoons of baking soda for each

The ingredients for elephant toothpaste are pretty high. But i still have the feeling that the mini firecracker solution could work better, easier and much cheaper. Or are my feelings in the wrong direction?

After some more tinkering... the materials used in smoke bombs can do the trick. But maybe too hot for too long time.

I understand that a expanding volume in a closed space can be dangerous. So i can see why you want to be on the safe side with your information. The more efficient solutions are not for kids any more i guess... But i just thought i ask here before i go to the anarchists forum. Joking

[Enthalpy]

A pump for bicycle tyres would be best, but I don't see how to seal the many bottles.

Natural yeast and something to feed it. I fear the rests will rot.

Yes, bicarbonate or some carbonate and some acid like vinegar. More concentrated acid would leave less water, so the bottle lifts more weight.

Firecrackers are not my first choice. The corrosive gas, especially SO₂, may harm the plastic bottle over time.

Please protect your ears. Once with friends, we let soda bottles explode by pouring liquid nitrogen in and closing. My friend stayed deaf for half a day as he went too close. How much luck he had with shrapnel, I don't know.

Use scales to measure the amount of baking soda and acid so the pressure is reproducible. Cheap on eBay or Alibaba. Pour a clear excess bicarbonate to leave no acid damaging the plastic. You can prepare many doses in advance.

Did you check how durable the bottles are under sunlight? A protection by the pier can be useful.

Let a pier-review check your design.

[EDsteve]

Hello Enthalpy,
and thank you for your answer.

Natural yeast and something to feed it. I fear the rests will rot.

Last night i put 1g dry yeast and a bit sugar water (2cl) in one bottle . The result looks promising. Can you explain your "fear" about the rotting situation?

As already mentioned i tried the baking soda and vinegar(25%). But the pressure is way to small compare to the amount i have to put in each bottle.

Did you check how durable the bottles are under sunlight? A protection by the pier can be useful.

Yes. I already built a hot water solar heater from empty bottles and they do last quite a while (more than 5 years in direct sunlight). But with the peer they will be covered from all sides. So that should be fine for a long time.

Let a pier-review check your design.

I am still not exactly sure what it will become. Peer, floating platform, catamaran style boat or even an island. I will start small scale first and built two pontoons with 4m lenght and 60cm diameter. After collecting some experience how it behaves i will decide in which direction i go from there.

As you can see in the attachment. I am still in the beginning phase

[Enthalpy]

I put 1g dry yeast and a bit sugar water (2cl) in one bottle. Can you explain your "fear" about rotting?

If you leave organic materials in a bottle for years, bacteria transform it into stinking and badly looking compounds. An exception would be if voluntarily introduced bacteria, for instance yeast, produce enough alcohol to kill all bacteria in the bottle. That's why you can keep wine for years (it will turn to vinegar but keeps safe for drinking).

I didn't check how much water is needed. While producing CO₂, alcohol is made too, and some 14% alcohol stop the fermentation as the bacteria die.

I tried baking soda and vinegar(25%). But the pressure is way too small.

Vinegar is a very dilute acid, you need too much of it. Take a more concentrated acid, but please be careful. Prepare some means (the Ocean) to rinse yourself immediately. Wear protective goggles.

I prefer much the less strong polyacids like citric acid, tartaric acid
https://en.wikipedia.org/wiki/Citric_acid
https://en.wikipedia.org/wiki/Tartaric_acid
More protons hence gas per kilogram, less dangerous.

Oxalic acid is more caustic
https://en.wikipedia.org/wiki/Oxalic_acid

Battery acid (=sulphuric acid) is cheap and available but dangerous, and you need more or it for the same gas amount. Try to avoid it.

Can you compute the amounts? Introduce an excess of baking soda, as it shouldn't damage the plastic over time.

[billnotgatez]

@EDsteve

Your bottles look like plastic water bottles and not plastic soda bottles.
I now notice you said that in your original post.

I thought that not all water bottles had the same pressure requirements as bottles with carbonated drinks.

[billnotgatez]

A side note
Different varieties of yeast tolerate different levels of ethanol.
I expect the best are pricey.
It seems to me most any yeast will keep most bacteria count down.
I am betting that enough carbon dioxide would be created before death due to ethanol level.

[EDsteve]

@billnotgatez
You are right. I don't use soda bottles. Water bottles are just more common here. But also these bottles are stronger then we might think. A full bottle falling from 10m. No harm. I was jumping on a bottle. No harm. So i am pretty sure they can handle much more than 1 bar easily.

@Enthalpy
Thank you. Your post really helps me a lot. Citric acid and Oxalic acid is very cheap (1,3USD per KG). And if i understand you correctly. Oxalic acid is more efficient for my case but also more dangerous. Correct?

Can you compute the amounts?

My skills in chemistry are pretty low. So i would just start small and do some try and error. But if you have a rough idea. I would start with that first
I also started a course on https://www.khanacademy.org to gain more knowledge.

[Enthalpy]

I expect the best [varieties of yeast] are pricey.

Grow the yeast

Anyway, I prefer the bicarbonate and citric or tartaric acid method.

I am betting that enough carbon dioxide would be created before death due to ethanol level.

It's a matter of water and feed amount compared with the bottle's volume.

Your bottles look like plastic water bottles and not plastic soda bottles. [Not] the same pressure requirements.

Well done! Inadequate for 1+1atm.

[Enthalpy]

Oxalic acid is more efficient for my case but also more dangerous. Correct?

Oxalic acid saves a little mass but is much more caustic to your skin and eyes. Citric or tartaric acids are much safer. As you find them, prefer these, absolute clear choice.

Wear a scuba diving mask to protect your eyes.

My skills in chemistry are pretty low. So i would just start small and do some try and error. But if you have a rough idea. I would start with that first

Many people here can help you compute the amounts. Normally on this forum, we shouldn't give you the ready-to-use answer.