Please watch this short video to learn more about the science behind the Horst Miracle Gauge:
Here’s a good analogy:
PIcture a 6” high glass filled with 4” of water and a straw in it. If you put the straw in your mouth and start blowing, you see air exiting the straw in the form of bubbles. What happened?
Let’s slow the process down.
Starting off, the level in the straw was equal to the water level in the glass.
As you increased the air pressure in the straw by blowing, the water level in the straw went down until the air exited the straw in the form of bubbles.
You can never increase the pressure in the straw more by blowing harder, because all the extra air goes out in the form of bubbles.
If you suddenly put your tongue on the straw, the water level in the straw will not come up. This is because air is trapped inside the straw, and water can not come back up.
If you visualize a pressure gauge connected to the inside of the straw, the air pressure would be equal to the water pressure at the bottom of the glass.
The air pressure is not measured in psi, which is what you may be used to. It is so low that very little air pressure is expressed, whether in barometric pressure, or also in inches of water pressure. The higher the water level, the higher the pressure. One (1) psi is equal to 27.68 inches of water pressure, so 1 inch of water is 1:27.68=.0361 psi. So with our 4 inch example, this comes to 4 x.0361=.145 psi. Thus, the Horst Miracle Gauge would show four (4) inches. That is the level of the water in the glass.