Why do i need to lap my silver polyblock
 

Why do i need to lap it?? .. The silver looks pretty thing....

You only need to lap the bottom if it seems rough.
-Kev

Actually its all bout how flat it is more then rough. Many of the nicely polished blocks out are actually not flat at all. People seem to think Polished and smooth is the same as flat. its not.

You CAN have a flat and smooth/shiny surface but you need to use sand paper by hand on a perfecly flat surface ( a granite slab works nice), or use a real lapping machine and lap it up above 1200 grit.

Putting it on a polishing wheel WILL make it shiny but will make the surface all warped and not flat at all. N8 shows on his site a real lapping machine and how it took a Cu plate down to exactly flat. ( I will link to his site later when I get home).

Heres the deal take a straight edge ruler and place it going diagonal from corner to corner and have it set on a table. Look exactly perpendicular to the cold plate ( looking across it) and see if you can see ANY light coming from in between the ruler edge and the plate. Do that from both directions diagonal, and then a few times just across the center from side to side.

If you find the plate is bowed, or not flat, then you can do one of 2 things:

1. Call the guy you bought it from and ask fer your money back.

2. Get a glass plate or some other hard and flat surface, and some sand paper and get at it.