ATM a few points

[Ina Ron Lippard Renaissance Reproductions <renrepro@together.net>]

   Just a few points.
First, about tubing. Why can't you take a cardboard tube the right size and
gel-coat it with clear fiberglass resin? It should sink right into an unwaxed
paper tube. It you add a pigment to it you got any color tube finish that will
not fade, and looks better then ,ummm, grey. Star maps look nice.And it
will be very strong! Well stronger then the cardboard!
Second. If you add something to the concrete it may be tougher. Like granite
sand for instance.
  OK so it's three. When you grind, the first thing you do is grind the
mirror.
The second thing you do is grind the grindings! So what you do is re-charge
more often. I do this. I add more grit and more water on my balls. I also add
some dish-washing deturgent, liquid deturgent that is. It foams. The bubbles
actually cause the grit to cling more to the sphere I'm grinding. I use a 
cheap soap.I also use it to cut quartz in a diamond saw for a different
reason.
It is a real good lubricant! For grinding use 3 drops liquid deturgent every
other wet. For glass-cutting such as trepanning out a blank, use 1 bottle per
each ten inch plate-glass blank. It will work. Just remember to use some
water!!.
CS, Ron