Sheeting is a particular form of water behavior. Thanks to the interaction between a liquid and a surface, sheeting can occur. This means that the water glides off the surface like a big “sheet” of water. There are a few different things at play that cause sheeting, but it is a popular effect that protective layer can give.
How does sheeting look like
When water is poured on a surface, it can glide off the paintwork like one piece of liquid. In some cases it glides off the surface as fast as it is poured on the surface. This video will show sheeting (and a bit of beading) in practice.
How does sheeting work
When a surface has a different surface energy then the surface tension from the liquid, the molecules in the liquid will pull harder at each other than the surface pulls on it. This causes a very small surface contact area, which prevents the liquid from having enough contact area to stick to the surface. The water isn’t repelled, but it pulls itself towards itself.
It is also important that the surface itself is very smooth. Any imperfections in the surface will cause a droplet of water to cling on to. An imperfection is made up out of microscopic hills and valleys. The water molecules can fill these microscopic gaps which causes the water droplet to get stuck. For proper sheeting the surface needs to be perfectly smooth.
This however poses a small challenge. Even by polishing it is difficult to get a perfectly smooth surface. So a protective product that helps to create a smooth surface helps. A wax is notorious for filling in gaps, and leaving a temporary smooth surface. Sealants don’t fill as much, but do offer a very slick layer. Ceramic coating don’t fill much at all, but offer a superior smooth surface.
All have their own properties, however durability and hardness plays a big role in maintaining sheeting.
Sheeting and the amount of protection
It is commonly thought that sheeting means that there is protection. This is not true. A surface can contain certain contaminants that won’t be removed with a normal shampoo, which has a negative effect on the sheeting. Also, a surface can become , which makes the water adhere to the surface more then it should.
This does not mean that there is no protection anymore, it just means that the requirements for good sheeting isn’t met anymore.
However, beading and sheeting are such popular traits, that many detailers will re-apply a layer of protection when the sheeting and/or beading is down to a certain amount.