Admittedly, a bit of a strange question if you already know what both terms mean. But stick with it for a few minutes and give us a chance to clarify.
If you know anything about ceramic coatings, then you know that one of its strong spots is its ability to repel water from the surface of the car. A hydrophobic ceramic coating is pretty much the norm.
But how or why that happens is sometimes not exactly clear. Well, let us start this one by first explaining what both terms 'hydrophobic' and 'hydrophilic' mean and how both terms became accustomed to ceramic coatings in general.
What does Hydrophobic mean?
The term comes from two words meaning water and fear. Well, fear of water is an excellent way of explaining how water behaves on a hydrophobic surface.
When water comes in contact with a hydrophobic surface, it looks as if the water doesn't want to stay on it and wants to escape as soon as possible with the path of least resistance.
You probably saw that effect many times in nature on various types of leaves. It would rain and you would see water just pouring from the leaves without the leaves actually getting wet. Even when the rain stops you would still see little water droplets of water on top of the leaves. Those droplets we call water beads. And we will come back to them soon.
What does Hydrophilic mean?
Naturally, it would be the exact opposite of the above. Think of your shirt getting wet. It would most likely darken a bit, absorb the water, and get heavy and, well, what else - wet! An example of a very hydrophilic material that you have most likely encountered many times is a sponge. Water would pour over it and it would just dring all of it up instantly. So instead of repelling water, it absorbs it.
Ok great, so now you know what both terms mean. And now you might have an eyebrow raised a little bit thinking of why the term hydrophilic would be used in conjunction with ceramic coatings. What?!
Is there a hydrophilic ceramic coating?
No. Well, not that we would know of. And if there is one, it sure is interesting to think about why that would ever be helpful when it comes to paint protection. It probably got mixed up with ceramic coatings because people mistake it for ceramics. For instance, if you take a ceramic plate ( the standard one you would use at home for meals ) and you break it.
You would notice the texture is not glossy and fine on the inside of the material, but the glossy material that you usually see when you think of ceramic plates is only a shell on the outside.
The inside material - while still ceramics, is very hydrophilic. When you pour water on it, it will absorb the water, much like concrete would.
All ceramic coatings are not only hydrophobic. They are sometimes even referred to as super-hydrophobic. Ok, great, now you know, but why are we making an article about this then?
Well, talking to a lot of customers and seeing what people think in general regarding this topic made us decide to write a simple and all-in-one explanation on the subject and clarify all this confusion for anyone that was looking for some straight answers.
Remember the term 'water beads' we mentioned earlier?
What is water beading?
Well, as you probably have seen, when you pour water on a ceramic-coated car, the water looks as if it is trying to escape from the surface, leaving it dry.
But as with before mentioned leaves - after the chaos dissipates, sometimes, more often than not, you are left with water beads on the surface of the car. On the other hand, sometimes you would see the water behave completely differently.
What is water sheeting?
Instead of water trying to escape the ceramic-coated surface in an erratic manner as if it was escaping for dear life, leaving stragglers ( water beads ) behind when water is introduced - the whole surface gets completely wet, and then the whole water that is on the car would form one unified body that would drag all of the water from the surface of the car leaving no water beads. This effect is called 'water sheeting'.
So great for now we have learned that all ceramic coatings are hydrophobic, and none of them are hydrophilic. And now we have two new terms that compete with each other - water beading and water sheeting. Which of those two effects would you want more in a ceramic coating?
Short answer -
You want a ceramic coating that sheets more than it beads. Why?
Let us jump straight to the long answer to explain -
When it comes to water beads, you might think, 'What is the big deal? The beads are just standing there. They are not making the car wet or dirty. Why would I care?'
Well, you shouldn't care, at least not immediately. But once those water beads start to evaporate they would leave all the minerals that were in the water baked onto the surface of the ceramic coating.
Those white marks that are leftover we call water spots.
If the rain was acidic ( depending on where you live or the current weather conditions ) what you would be left with are called etch marks, and they are more aggressively damaging to the ceramic coating that you worked so hard to install on your beauty.
And while you can avoid all of that by removing the water beads from the car with various methods. You could use a microfiber towel, you could use a leaf blower, or even a hairdryer to blow the beads off the vehicle. Or you could take the car for a quick drive around the block to get all the beads from the car. It is not hard to do, that is true. But it IS tedious! You have to do it! Or else risk water spots or etch marks. Unfortunately, distilled water doesn't rain down from the sky to avoid those problems. And also, sometimes you simply won't be able to remove it in time. Perhaps it is a sunny day, and a raincloud passes by while you are stuck at work, or you are at home but simply haven't noticed your neighbors' water sprinkler spraying your car.
When you think about it, there could be thousands of reasons why you could end up with a potentially damaged ceramic coating or a the very least a dirty one until you have cleaned the problem away.
This is where water sheeting shines! Because of how it works, it usually leaves a very low amount of water beads on the car. And if the water sheeting effect is strong enough, it will leave no water beads at all, leaving the car completely dry no matter how wet it gets!
Sometimes you would see people use the term water sheeting when performing hydrophobicity tests on various materials and testing the durability of coatings while they damage when with different chemicals and such. They would say that The water is starting to sheet more than it was beading as the coating loses its structure, and thus its hydrophobic properties weaken.
This is misleading and probably a misuse of the term that leads to confusion. This is the reason why people usually aren't looking for water sheeting in ceramic coatings.
So, what determines if the ceramic coating will have water beading or water sheeting properties? This is what is called the sliding angle.
Sliding angle. What is it?
The sliding angle is the tilt at which a water bead of a specific weight starts to slip off your automobile. A bead will roll off more readily if the angle is lower. As previously stated, contact angle alone cannot tell you how high or low a sliding angle is.
There are several variables at play, including the droplet's weight, breadth, and gravitational acceleration, to name a few. As we mentioned before, water beads left on your finish might cause harm to your finish.
When beads have a low sliding angle, however, they simply glide off your automobile before causing any damage.
With this in mind, the sliding angle of a coating's hydrophobicity soon becomes an essential factor. When you consider the variables we outlined previously, the sliding angle becomes much more critical.
Because of the principles of gravity, the sliding angle tends to decrease as a body of water becomes larger and heavier.
That's why water seems to jet off of your finish when you hit it with a pressure hose or why rain rolls off your automobile easily in a deluge. Small beads, such as those from light rain or a nearby sprinkler, have the most difficult time sliding off your finish since gravity isn't on their side. So, if a bead of water doesn't have a significant gravitational pull behind it, how can you reduce its sliding angle?
You must meticulously re-engineer the car's transparent coat, changing its structure on a nanoscopic level. In that manner, you may produce a surface that is so smooth that practically nothing can attach to it, not even the smallest water bead.
And some ceramic coatings have the ability to do just that! They usually come with a price tag attached. But if you want a top-quality ceramic coating that you will be very happy with for a very long time, then you might just start thinking about adding a few more of those greens instead of paying for the cheap stuff. Not that cheaper coatings are automatically bad, or vice-versa. We have proven that by testing various ceramic coating products.
If you want to check our top list of ceramic coatings that we have personally tested and reviewed, you can read this article here.
We hope you find the best ceramic coating product that will satisfy your needs and that you will be happy with.
Also, just to throw this in here.
Because water sheeting does such a great job in removing almost all water from a coated surface and because ceramic coatings are super-hydrophobic, some people believe that it is a good idea to ceramic coat your windshield, so you do not have to worry about rain or dirt anymore!
You can read this article here to get our opinion on whether you should ceramic coat your windshield or not!