Rubbish in glass material...

[Behemot]

I'm novice in 3ds max,thus maybe answer to my question is self-evident.How can I get rid of those unwelcome black elements that appear in rendered glass material?????I used different materials - made on my own, from tutorials, from the net, to no avail.I made a scene with glasses with otherwise looks photo-realistic;constructed with lathe (with open spline,closed spline and symmetrical mirror image - results always similar...);I also tried building the glass by combining a cylinder and a tube - much the same...I tried manipulating all settings I could find in all materials I applied;the black particles grew bigger or shrank,but never have I managed to annihilate them totally. Oh,I forgot - this black stuff appears in the thick bottom of the glass,the rest(thin glass) is clear.
What can I do about it?????please help me,I'll thankful
Bruce

 

[leonec]

what kind of environmental background to you have? try rendering it again but do not include that background there is a check box for this in the material.

 

[Behemot]

I couldn't find the check box you wrote about,so I looked for other means of excluding the background from rendering,but with no effect.I use MAX 5.0, maybe it's arranged differently here or maybe the program has a bug.
In render menu bckgrnd colour was default black,I experimented with the colour even maps and ambient light,the unwanted concentric chops changed the shade but never disappeared...