how do they paint those large photos and ads onto the side of buses?

[scm1001]

Going into London I was struck by how many buses had advertising for new films etc all over them. It appeared to be painted directly on the metal rather than as a poster. How do they do that (some sort of printing process?)?

[SirRay]

I believe you saw vinyl advertisments applied to the bus, as shown in the link
Very common in America, too.

Vinyl Ads for vehicles (http://www.adsonwheels.com/BUS_Wrapping_main.asp)

[scm1001]

yes thats the stuff - from the site thay say its some sort of vinyl wrap. Would still love to know the details. I imagine they print it in rolls, but how do they get the rolls to register over the contours of the bus (anyone who has ever put up wallpaper will know the problem)? How do they stick it to the bus and remove it afterwards?

I teach a polymer class and those sort of details are great to include in the course

[scm1001]

just found this link (once I had the key words bus wrapping it was much easier). http://www.valleymetro.org/Transit/SchoolOutreach/buswrap/wrapping.htm

much harder than wall paper!

[DougC]

- - - There are computer systems specifically for producing vinyl vehicle decals. The system includes a big (36"wide or bigger) plotter-style cutter and software. The software contains 3-D models of vehicles, so you just arrange the way you want the (flat) image to look, and the software warps and cuts the pieces out so that when applied correctly, they will fit together--even over a compound-curve surface. Google "vinyl decal system" for hours of fun.
~

[Blueapple]

You can get paid to put them on your car.
Ad Wraps (http://www.ad-wraps.com/)
Site for you UK'ers (http://www.ad-wrap.co.uk)