White box important question.

[ParoXysm]

I built a white box in which I did put a black cardboard and a sheet of plexiglass on top of it (to create a reflextive effect of the object in it).
I need to take three different pictures of three different objects which one of them is entirely white.
I already took two pictures which are just great, but I can't seem to take the picture of the third object properly... It's so dark all around the with object instead of a drak grey.
I'm using white 6400k bulbs with great diffusers. I have a grey cardboard to set the White Balance manually, but nothing works perfecly.
Does anyone has the answer I need? I can also use a flash if needed.
Thanks

 

[minicoop1985]

Have you tried a longer exposure? Just a thought-doesn't hurt to try on a digital camera.

 

[ParoXysm]

It worked much better, thanks

Have you tried a longer exposure? Just a thought-doesn't hurt to try on a digital camera.