What could be added to tap water to reduce air bubble formation on a submerged object?

Question

Submerge your hand in a bucket of water. Some air bubbles appear immediately and others add to the surface of the hand over time. Is there anything that could be added to the water to reduce the creation of air bubbles on the object? (additive/admixture). Alternatively, what could be added to the surface of the object (i.e. hand) to reduce adherence of air bubbles.

I did some searches and came up empty-handed. There is some information about anti-foaming agents (copied below) but did not seem like they would work for this purpose.

Thanks for any suggestions for things to test! Especially if they are commonly available.

-John

(search strings: additive OR admixture to prevent air bubbles formation OR formation water hydrophobic OR hydrophilic -concrete)

There seemed to be a lot of analysis of bubbles in concrete, and about defoamers in paint. But it was not clear whether these would help with my problem.

Here's an excerpt:

"Defoamer Composition

Almost every waterborne paint system contains an anti-foaming agent, typically in the concentration range of 0.05-0.5% by weight.

The composition of defoamers is extremely diverse. However, characteristic components of defoamers include the following:

One or more hydrophobic compounds. The hydrophobic component destabilizes the foam dispersion because it displaces the stabilizer. Hydrophobic components are considered among the most active ingredients in defoamers.

Also, hydrophobic components prevent the formation of stable interfacial surfaces between air/liquid. Consequently, the air bubble can penetrate the interface and release itself or it can form a bigger, less stable, air bubble by coalescing with another air bubble. Typical hydrophobic components are mostly solids, such as silicas, polyamides and waxes.

Mineral oil. The mineral oil acts as the carrier for the hydrophobic components. Surface active dispersing agents/emulsifiers. The dispersing agent ensures an optimum distribution of the hydrophobic component in the oil while the emulsifier eases the spreading of the defoamer throughout the medium to defoam. "

Answer 1

The (very small) air bubbles you see sticking on your hand when you immerse your hand in tap water, are of two types:

1- Bubbles which contain air outside the water. This air is trapped along your fingerprint lines when you insert your hand inside water. Typically, the lower the surface tension, the lower the probability and size of these bubbles. You can effectively decrease the surface tension of water by dissolving washing powder or soap to it. Interestingly, this will cause a lot of bubbles to form ON the water, but very few UNDER the surface.

2- Bubbles which form due to dissolved gases in the water itself. Contrary to solids, gases dissolve better in a liquid at it's temperature decreases. Boiling the tap water and then letting it cool in very low pressure conditions will remove most of these gases and keep them from forming again.

So, as a conclusion, boil the water, cool it under low pressure conditions and then add washing powder to it. Do not stir the water after adding it and just give it time to dissolve by itself. Now slowly insert your hand inside the water. There would be far fewer bubbles on your hand when it gets in.

Answer 2

I suspect the little bubbles are actually CO2.

CO2 is water soluble, and you could find it in most forms of tap water. "hard" water tend to have high concentrates of CO2 while softer water have less.

If indeed this is the case, the bubbles form because it is energetically efficient to them to adhere to your hand, which is a lower energy state for them.

I suspect what one might do, is make it more attractive to CO2 bubbles to stay in a solution state. One might do that by adding an agent that "binds" better with the CO2.

Try salt. it is widely known that soda-water have a lot of salt to increase the solubility of CO2 in the water.

Failing that, try to research water soluble materials that bind CO2.

Answer 3

These bubbles are any gas that is "in" the water. I heard about this in the context of "not enough oxygen in water for fish". (Yes, your question is the opposite, but maybe you can find some hint searching in this context, "Limnology" is the physics of lakes etc.)

I see two points you could use - or maybe both:

1. de-gas the water Run the water through a low pressure region and "suck" out the gas. You might have to check how long it takes for the gas to get out.

2. use a smooth surface coat the object that should not have these bubbles on with a really smooth material. Additionally add an object with a really rough surface to the water container: this one should take a lot of gas out of the water.

Answer 4

Simplest solution for obtaining water that is nearly bubble-free: Heat water to near boiling to drive out the dissolved air and other gases. Cool water, then carefully pour into final container, along with a drop of liquid detergent.