The best method to
these two species is under a scope
contained in botanical keys.
However, if all
you need to know is whether or not you have oak suitable for use
in boats, you can accomplish that just as well using a razor
blade and 10X hand lens.
The 10X hand lens used in sunlight will
provide much greater definition than these photos.
What makes the White Oak group of oaks suitable
for marine use (and oaken barrels), is their large, earlywood
pores (the fresh, new wood formed each Spring) are clogged with
whitish, waxy tyloses that water won't penetrate. The Red Oak
group of species lack these tyloses, allowing water to penetrate
and the wood to literally weep and seep at the end grain. This
combined with other factors causes the Red Oaks to be subject to
the rapid onset of mold, fungus and rot.
White Oak end grain. Note the whitish tyloses
clogging the large, earlywood pores forming the pith or inner
edge of each annual growth ring.
More White Oak end grain.
Red Oak end grain. Note the relatively clean earlywood pores.
A home method to test for Red Oak is to cut it into short soda
straw sections and see if it will blow bubbles into a glass of
water. This generally isn't a very reliable method because
sawdust from crosscutting the sample often clogs the pores. If
you use it, then slice away the end grain and any sawdust
contamination first using a razor blade. The 10X hand lens is
Blackjack Oak. In the Red Oak group but here the pores are
clogged with sawdust, not tyloses.