What exactly is a "drying agent"?

[bcwang]

I've read some posts here about a drying agent used during an automatic car wash. But I still haven't figured out what it's supposed to do.

-Does it bead the water so the blower will shoot all the beads of water off the car? (I thought that's what clear coat protectants or surface sealants do)

-Or does it sheet the water so it drys without spots?

-What part of the car wash is this usually applied, and how can you tell when it is used?

 

[rph9168]

Not many IBA's use a drying agent. A drying agent is most commonly found in tunnel washes. Normally they simply reduce the surface tension of the water on the surface of the vehicle and make it easier for the water to be removed by the dryer. There are two basic types. The most common causes the water to bead. The less common causes water to puddle which allows the water to almost remove itself due to the larger mass pulled down by gravity or release as the vehicle moves. It was most commonly used in older in-bays that did not offer a wax/protectant or in some self serves.

 

[BillClinton]

My IBA uses spot free rinse at the end and it seems to stick to the car (not bead). Would a drying agent be used instead of spot free? Would it only be used on a selections that didn't get the dryer?

 

[rph9168]

Spot free rinse is essentially free of the solids that are normally found in water. Untreated water contains solids that increase surface tension, thus beading. The reason your spot free rinse appears to stick to the vehicle is that there is little surface tension due to the purity of the water so it is not repelled from the surface as hard water is. In reality, hard water would rinse more quickly but would leave spotting.

If your spot free is working properly any residual water left on the surface would dry without spotting. Do not apply any drying agent or protectant after the rinse. Many old time tunnel car washes used to use a fine mist at the end as a setting arch to assist beading. Some tunnel washes that towel dry a vehicle do use some drying agent in the final rinse so there is less water on the surface when the car exits the wash. Since many tunnels now use spot free water as a rinse this practice has almost disappeared.