Mirror Rendering

[auchifai]

Hi all, i have my model done in sketchup and have it exported to kerkythea for rendering. I m doing a design of a toilet and i have put a mirror in it. In kerkythea I have set this mirror as dielectric glass and it gives a fairly good results in reflecting the other side of the toilet. However, i do not know why there is always a round patch at the middle of the mirror. I am not sure if i have set the mirror property wrongly.

I have attached an image of my rendering at the corner of the mirror. You can see the round patch there.

Can anyone give me some suggestion on this?

Thanks in advance.

---

[massimo]

How is made the material? Also have you checked the model? (no backfaces, no smooth etc.)?
Here is a SS of a correct mirror material.