Things are a little slow so I will ask a basic question I have after watching Steve Goodson's mouthpiece video again. 

On a metal mouthpiece, you can use a Sharpie marker to help check for a flat table. What works on hard rubber or when practicing on plastic mouthpieces?

Sent from my iPhone. Siri is responsible for all goofy words.

You could try pencil scribbles.

I just look at the the scuff marks left by the sandpaper on the mouthpiece table.   

You need to use a straight edge too to check if it is convex.  It can be convex and your (poor) sanding technique can clean off all your applied table coloration leaving it still convex.



> On Feb 19, 2015, at 4:12 PM, Everett Fidler grassinospam@gmail.com [MouthpieceWork] <MouthpieceWork@yahoogroups.com> wrote:
> 
> Things are a little slow so I will ask a basic question I have after watching Steve Goodson's mouthpiece video again. 
> 
> On a metal mouthpiece, you can use a Sharpie marker to help check for a flat table. What works on hard rubber or when practicing on plastic mouthpieces?
> 
> Sent from my iPhone. Siri is responsible for all goofy words.
> 

Yes, rocking the mouthpiece while pulling it across the paper could create a convex surface where the marking dye (not Due, thanks auto correct) is all removed. I was hoping for something easier to see than sand paper marks when checking for low spots. Unless there is a second, a straight edge and pencil graphite is what I will try.