How to Create Fog on Glasses

Question if you create it whats natural about it?

Serendipity ! Thanks to you for that note on open tubes, it would allow me to use my telescope in cold-humid conditions, I'll do a little more research on the matter.

Just to add another factor to your project, consider that when water condenses on windows, it forms small droplets (fogging). This is because the window is hydrophobic. Thin transparent coatings (such as Rain-X) can be applied to the window to make the surface hydrophilic. When this happens, condensed water will form a film and will not impair vision.

My understanding is that Rain-X creates a strongly hydrophobic (repels water) surface layer which causes the water to pull together into droplets that run off, leaving a clear dry water-free surface. This is optically non distorting. Normal glass has silicates which bond to water molecules (hydrophilic), causing waviness in seeing through it because of the varying thickness of the water layer.

I think you have it backwards. A surface that fogs at the dew point temperature is hydrophobic to water and is not wet by the droplets condensing on it. A series of these droplets is called fog and is an array of micro-lenses. If the same conditions exist on a hydrophilic surface, the contact angle between the water and the condensing surface is smaller. The water wets the surface and forms a continuous sheet that is transparent.

Have you tried using Rain-X? I use it on my car windshield. I live in a "frost pocket" where radiational cooling creates a locally lower temperature in the air, with the result that frosting or fogging (depending on the glass temperature) of the windshield is very likely in the morning. The apparent disagreement between us seems to be in the details of whether it is easier to see clearly through a hydrophilic or a hydrophobic surface. A fog can be created on a hydrophilic surface by preferential condensation onto the micro-surface of the protodroplet, making the droplet grow. The area of the windshield which is not wiped by the windshield-wipers has a later of deposits which cover the Rain-X and create a hydrophilic surface, whereas the area inside the wiped area has exposed Rain-X, and is hydophobic. This provides an opportunity (before the wipers are used) to examine the differences nearly every morning - and I do. Do you?

My bad, you are right. However, from "The basics of Physics" by Rusty L Myers, "Conversely, in other cases substances may be used such that the adhesive forces are greater than the cohesive forces causing the water to spread. Wetting agents used in dishwashers are prime examples." I use a wetting agent in my dive mask to prevent fogging.

just use a small table top humidifier and a lab stand to hold the glasses above it

Please clarify (!) your post. Are you desiring to create a fog behind lenses, or a fog on the surface of lenses? A post with more details in the question will receive more detail in the answers.

You can create fog by operating the lens below the dew point temperature of the ambient atmosphere. You can quickly clear the lens by heating it. A thin layer of tin oxide on the glass is transparent. If you run electric current through the conductive layer it will quickly clear the fog. This is how many window defrosters work.