why people add oil?

[Itoero]

People often use Baking Soda or KHCO3 as fungicide.
They solve it in water.
I add soap because it makes the water more 'wet'.
Many people add some type of oil instead of soap.
Why do they do that?
Oil does not mix with water and you can't solve baking soda in oil.

[Cole_Robbie]

Soap and oil both perform similar functions. They reduce the surface tension of water droplets, allowing them to spread farther. The oil doesn't mix with the water, but it sits on the surface of the droplet as it comes out of the sprayer. When the droplet hits the plant, it breaks apart and sticks instead of bouncing off.

This link is about spraying herbicide, but the science is the same with any water-based spray:
http://extension.psu.edu/pests/weeds...de-performance

[Gardeneer]

I also think that oil and soap makes a layer that probably the fungi cannot penetrate or insect won't like.
Probably you can add any vegetable oil. The other day I saw a fungicide /pesticide with sesame oil. But you have to add some kind of emulsifier to the solution.
In my oil and vinegar dressing garlic works as emulsifier.

Gardeneer

[Itoero]

Oil does not mix with water and is less dense so it floats on top.
In a spray with baking soda, water and oil, the oil will just float on top and will not be sprayed on the plants.
Oil is Hydrophobic.
It doesn't sit on the surface of the droplet. That's a nonsensical idea.

By adding soap, you create micelles in the water.
Those micelles change the surface tension.

[Ed of Somis]

Some interesting "theories" above. There are several reasons folks spray oil. Reducing the surface tension of water is not one of them. A non-ionic surfactant is best for that. Some soaps contain small amounts of this surfactant...to aid in the cleansing action of the soap.

[Itoero]

The things I said are science.
Again, oil is less dense then water and does not mix with it...unless you add soap of course.
That means that the oil is sprayed when the water+baking soda is already sprayed.
I doubt it's even possible to spray oil.

[Gardeneer]

If you can brake the oil molecules into smaller particles , it can stay mixed longer. That is how they make homogenized milk.

[Worth1]

I was going to say to keep their engine from locking up.
Worth

[Cole_Robbie]

Originally Posted by Itoero

It doesn't sit on the surface of the droplet. That's a nonsensical idea.

The things I said are science.

https://en.wikipedia.org/wiki/Surfactant

[Worth1]

Originally Posted by Gardeneer

If you can brake the oil molecules into smaller particles , it can stay mixed longer. That is how they make homogenized milk.

It is also what happens in an engine or transmission when water gets into the oil.
It turns it to a milky like substance that wont separate.

Worth

[Worth1]

Originally Posted by Itoero

The things I said are science.
Again, oil is less dense then water and does not mix with it...unless you add soap of course.
That means that the oil is sprayed when the water+baking soda is already sprayed.
I doubt it's even possible to spray oil.

Have you ever heard of oil mist?
Why couldn't you spray oil?

Worth

[Gardeneer]

I remember a pesticide called "Vick's Oil" or something like that. But you had to add water to it to spray. That is what NEEM oil is too.
Why not just spray whole milk , mixed 50/50 with water !! I used to use it on squash and cukes to prevent Powdery Mildew.

Gardeneer

[Itoero]

You can mix oil and water but you need to treat the water or add an emulsifying agent first.
Baking soda does not dissolve in oil.