Snow foaming or pre foaming is the process of covering the exterior of your car in a designated cleaning product in foam form before washing it to help remove and loosen dirt and contaminants. Pre foaming your car is actually one of the most important parts of the wash process but unfortunately it is still not undertaken as much as it should be. The main reason you should pre foam your car is that it helps to loosen and pick up dirt from the surface. These dirt particles become encapsulated by the foam and are lifted off as it runs off the car.
If these dirt particles are not removed before washing then they will be worked all over the surface during the wash process causing light scratches and swirl marks. You can pre rinse your car with a hosepipe or pressure washer and while this is much better than nothing, it is nowhere near as effective as foaming at loosening and lifting off dirt and contaminants.
Some pressure washers have a chemical injection system which allows detergents to be premixed with the water. These can be used to pre foam your car and it is much better than simply rinsing, but unlike a designated foam lance attachment there is no air injected into the mix so it will not foam up and be able to cling to the surface to the extent that a designated product can.
There are a range of different foaming products and foaming lance attachments available and the strength and thickness of the foam can be altered according to the level of detergent that is used and how the lance is adjusted via the air injection control. It is important to pre foam your car when it is dry as this allows it to cling to the surface for longer and effectively loosen and remove the dirt. If applied to an already wet car the foam will simply slip off and will not be able to do its job properly.
All areas of your car should be foamed including the wheels, tyres and arches. Once a sufficient level of foam has been applied it should be left to dwell for a few minutes until it begins to run off and disappear. After allowing it to dwell you should thoroughly rinse off the remaining foam with a hosepipe or pressure washer. Ensure all residue is removed and be very thorough, as you want to remove as many dirt particles as possible before washing to prevent them from potentially being worked all over the surface and causing damage.
You can often see the level of dirt and contaminants that have been effectively removed by the foam as it runs off the vehicle. If the vehicle is particularly heavily soiled then you can reapply the foam after the first application before the rinsing stage.
Foaming is also very useful for cleaning larger vehicles such as caravans, boats or trucks as this is what it was initially designed for. The foam can reach awkward areas and can then be rinsed off with out having to try and access them by hand. You can also use the pre foaming technique to clean other things such as house guttering & fascias, conservatories and greenhouses for example.