The Bird Man said:
How do you restore/create dome on a disc?
I put the disc inside a large mixing bowl, with a near airtight seal when pushed in(bottom of disc facing up). I then placed a wine bottle in the center of the disc to weigh it down. Anything round and heavy will do the trick. Keep in mind the size and weight of different objects would change the shape a bit. Then I filled the bowl with HOT tap water, topping it off with boiling water every so often. Kept it hot for about an hour, then I let it slowly cool off for about 6 hours. Pull it out and you have dome!
There is a whole thread about disc shaping somewhere on here, but no search function to find it...