Hello, I want to render a white material and it renders gray.
I know it’s common but. ¿how do I get a white material?..without emitting.
You could increase the reflect value (Shaders>Ref) to make something “whiter”. You can also reduce the Specularity and Hardness to very low values - but if you want it to look 3D then it has to have highlight and shadow and that means grey (or some shadow colour).
You could also increase the amount of light energy shining on the object so that more white light is reflected to the camera. Better still, shine warm light (yellowish) on one side and a duller cool light (bluish) on the shaded side.
If you’re rendering a single object with no background or environment, try changing the world colour to something very dark rather than the default “hideous blue”.
The problem is there’s no such thing as “white material” when you’re representing objects in a 3D environment. All colours are only relative to their environment and the light shining on them.
Hold up a pice of blank newspaper and ask someone what colour it is and they’d likely say “white”. Then hold up a piece of photocopy paper and ask the same question. Again the answer will be white. Then hold up a “white” plastic container - same question, same answer. Put all three items side by side and only one of them will still appear to be truly white, the others will look quite grey by comparison. Things get even worse when you have some in a room with an incandescent light and others in a room with fluorescent lighting. Nothing is truly white in either room but our brains make allowances. As a landscape artist I know that snow in sunlight is often yellow or pink (ish) and in shadow it’s blue or purple (ish) - usually. Most people would just see it as white despite the obvious contrasts.
What all this means is that your Blender object will appear white if the lighting and environment accurately portray a given situation such that the viewer can just accept it for what it is.
I would’ve just said “make it shadeless”…
I always have problems with getting white as well.
If you speak German you can find something here:
http://blendpolis.serverpool.org/f/viewtopic.php?t=10443
If not, take a look at the photos. I think they are pretty much self explaining. Ask your questions … 
Best regards,
Martin