Andy Dingley wrote:

I use the phenolic (brown) microballoons, not the white silica ones.
They're much softer and don't dull tools.

For probably 90+% of the people on this list, that is probably a good
idea to use the phenolic balloons since the usage is small.

I buy microballoons in 4 cubic ft bags(30 lbs), often geting several at
a time.

The increase in cost of phenolic is significant.

Lew