Help! Plaques don't come up.

[Zhong Zhao BioChem]

Hi. 

I am preparing filters for screening Rat Genomic Library. However, I have
a problem in getting good plaques on plates.

After overnight in 37C incubator, I see nice plaques but all of them are
below the surface of topping agarose. The surface of the topping looks
very shinny. I tried to adjust the topping agarose temp and different
agarose and all failed. 

Since I do not see plaques on surface, I decide not to make filters since
there may be nothing there.

What goes wrong here?

Please help.
Thanks much.

John.