"Doug Miller" wrote in message news:9ff0e.13497
There are at least two more ways to tell: tempered is a *lot* harder than
standard. And it's noticeably heavier, too.

This doesn't help much if you have only one piece, and you want to know if
it's tempered or not... but if you have two pieces, one tempered and one
standard, it's pretty easy to tell which is which.

Perhaps, From what I was told when I used that same analogy is that because
hardboard differs greatly in appearance from different oils, chemicals, or
wood products that are used and depending on manufacturer and location , the
hardness's will also vary quite a bit. Basically if you have different
brand hard boards the hardness of one may or may not indicate which you
have. If both are from the same manufacturer your method would be more
accurate. Either way I would use this method if having to decide which to
use but if a specific specification is indicated it would be better to be
able to accurately validate.