Sorry for such a noob question but I was wondering... Why do you put masking tape on the car when you wash it?!

 

i don't believe that it's used much when washing, but when polishing and/or waxing, to protect plastic/rubber trim.

however, many of today's waxes mention being safe for these surfaces now, so perhaps it's only for the polishes?

 

yup- not for washing...

and yes, for polishing-
also to keep product outta the "cracks" (inside hood, etc.), and emblems, and as philbert indicated trim pieces (parts that do not get polished).
and to mask off areas that need more work than others

i dont use it any more, and am just careful when i get near parts that could be masked, so its a personal decision whether to mask or not

 

I used tape to mask off areas I think a polisher shouldn't touch, like trim around where the top meets the body on a convertible. I also used some to split a hood in half during polishing for 50/50 shots. Some cars have trim that isnt friendly to polish/wax, and taping them off will save time and headaches.

 

The reason you don't want those areas to be polished is because they burn very easily. If it hits the tape, that's no big deal, but if it hits the plastic, it'll turn white and be burned. I know this because I burned my own plastic haha