the oaks; red, white, and live

There are, depending on what source you believe, somewhere between 600 and 900 species of oak but of course most of them are obscure and not generally available. At just a wild guess, I'd say there are probably 200 or so species world wide that are used for lumber and/or artisan work in the various countries of their growth range.

The basic types of oak can be categorized in different ways. The fundamental categorization is red and white and all oaks fall into one of those two groups. There is, however, a readily distinguishable third group that is actually taken from the red group AND the white group, and that is the live oaks. So, generally it is taken that there are three basic types.

red oaks --- ring porous with very little tyloses and strong rays
white oaks --- ring porous with plentiful tyloses and strong rays, more resistant to rot than red oak and suitable for wet cooperage because of the tyloses-closed pores.
live oaks --- diffuse porous with strong rays

telling live oaks from the others

"Live" oaks are called live because they keep their leaves throughout the year, unlike normal (ring porous) oaks which drop their leaves. Actually, I have it anecdotally that some live oaks do drop most or all of their leaves but are still classified as live oaks.

Live oaks can be either white oak or red oak, and they will or will not have tyloses accordingly. Live oaks are very easy to distinguish from normal (ring porous) oaks via the end grain. What I am calling normal oaks are are ring porous and lives oaks are diffuse porous.

Ring porous means there is a row (or several rows) of large earlywood pores at the beginning of each growth ring, abruptly changing to much smaller pores for the rest of the growth ring. You can clearly see this in the end grain cross sections below for red oak and white oak.

Diffuse porous means that the pores are randomly distributed throughout the growth ring or sometimes they are a bit more organized, such as the radial strands shown in the live oak below. In either case, there is little to no difference in size between earlywood pores and latewood pores and growth rings are often quite indistinct.

1/2" x 1/2" end grain cross sections

red oak --- ring porous with large earlywood pores, very little tyloses (but some pores clogged with dust)	white oak --- ring porous with large earlywood pores (a few open pores but most clogged with tyloses)	live oak --- diffuse porous with no row of earlywood pores (can be red oak or white oak)

red vs white --- don't rely on color
Color is NOT a good distinguishing characteristic among oaks. There are some pieces of red oak that you can tell are almost certainly red oak based on color and similarly for white oaks, BUT ... that is never 100% reliable. I have seen plenty of white oak that could easily be mistaken for red oak and vice versa. The rays in white oak tend to be longer than in red oak and quartersawn pieces can sometimes be distinguished by the ray flakes, with white oak being noticeably longer than those in red oak. Again, though, that is rarely a guarantee. If you see a very old piece of furniture, tables in particular, with really large, long ray flakes, you can bet money that it will be white oak, but otherwise, you might just be guessing.


"standard" red oak / Quercus rubra	a red oak that (based on color) looks like white oak


"standard" white oak / Quercus alba	a white oak that (based on color) looks like red oak

red vs white --- ray flakes on flat cut surfaces
Quite often on flat cut surfaces, rays will show up clearly and when they do you can almost always tell red oaks from white oaks because red oaks have relatively short rays showing on flat cut surfaces whereas white oaks have relatively long rays showing on flat cut surfaces. This difference in ray size on flat cut surfaces is often more reliable than the usually more pronounced difference on quartersawn surfaces. That is discussed in the next section.


2" x 2" sections of flat cut red oak showing the typical relatively short rays


2" x 2" sections of flat cut white oak showing relatively long rays (these two samples actually show rays that are slightly longer than normal for a flat cut white oak surface)

red vs white --- ray flakes on quartersawn surfaces
On quartersawn surface, the different appearance of the ray flakes can be quite pronounced, with white oak flakes generally being significantly longer (and sometimes wider as well) than those on red oaks. BUT ... note that I said "generally". You have to keep in mind that a few degrees difference in the angle of the rays to the surface can make all the difference in the world. I've seen almost-quartersawn white oak (and I mean just a few degrees off) with flakes that were shorter than those on some pieces of red oak that were perfectly quartersawn. This is illustrated in the next section.


4" x 4" sections of quartersawn red oak showing relatively short ray flakes the flake in the lower left of the second image, at over 1" long, is quite long for red oak


4" x 4" sections of quartersawn white oak showing relatively long ray flakes the longest one in the left image is 3" and in the right it is 4+"

red vs white --- an example where ray flakes
on quartersawn surfaces are not a reliable differentiator.
Unfortunately I was unable to find images that show exactly what I want but the next set of images is close enough, I think, to be convincing. I found a red oak that was just over 10 degrees off of quartersawn and a white oak that was just under 10 degrees off of quartersawn. Both of these pieces would unhesitatingly, and correctly, be sold as quartersawn. Based on the angles, you would expect the white oak to have larger surface flakes than the red, but it does not. Only a single flake on the white oak piece is 2" long (circled in the face grain image below) where as numerous ones on the red oak were 2" long (one such is circled in the face grain image below). If both were perfectly quartersawn, the white oak would show longer flakes. Statistically, this occurrence of red oak flakes being as wide/long as or wider/longer than white oak is an anomaly, but my point is that it DOES happen, so you have to be careful.


4" x 4" face grain of a piece of quartersawn red oak with one of the many long flakes circled and the end grain of the same piece, showing the angle of the rays


4" x 4" face grain of a piece of quartersawn white oak with the single longest flakes circled and the end grain of the same piece, showing the angle of the rays

red vs white --- using wood anatomy

At the level of shop work (sandpaper or a sharp cutter and a 10X loupe) red and white can be reliably distinguished by the fact that most pores in white oak show tyloses and those in red oak almost never do. This is much easier to see if you use a sharp cutting edge to expose the end grain rather than sanding because sanding will clog up the pores and obscure the tyloses. Even with just sanding, however, you can tell for sure that you have a red oak if a lot of the pores are obviously open in the end. If they are all clogged up with sanding dust then you might have either kind of oak.

tylosis (plural is "tyloses") is a shiny substance and the pores that are clogged with it look a bit like tiny little round windows that have been smashed up and glued back together with the pieces crooked. It is difficult on my own white oak samples below to tell that there is tyloses (even though there is) because I fine-sand my samples rather than using razor cuts and the pores are usually filled with fine dust which obscures the tyloses. To clearly show what the tyloses look like in white oak, I found a couple of pics on the Internet and use them here to show what the tyloses looks like and the difference between that and red oak which has no tyloses (the clogging in some of the red oak pores in both the pic here and the ones below in my own red oak samples is not tyloses).

When looking for tyloses, you should avoid the sapwood because white oak does not always have a lot of tyloses in the sapwood but it always will in the heartwood. Not EVERY pore will be clogged with tyloses at the point where you expose it, but most will.

end grain cross sections estimated to be 3/16" x 3/16"

red oak (very little tyloses)	two views of white oak with plentiful tyloses

red vs white --- the soda straw test
Another way to distinguish them is the "soda straw test". Just slice off a piece of oak that's say 1/2" long or 3/4" long and try to blow through it. If you can blow air through it, it's definitely red oak and if you can't it is almost certainly white oak. With a piece about an inch long, try blowing with one end in water and see if you get bubbles (red oak) or not (white oak). Adding a little dish-washing soap makes it even easier to see the results.

red vs white --- sodium nitrite
Yet another way to quite reliably distinguish them is a chemical test using sodium nitrite but I'm not going to go into that here since it's not something available just off hand in a shop. You can read about it on the Internet. (e.g. sodium nitrite test)

end of original article

A DETECTIVE STORY
Recently I was sent 4 pieces of quartersawn oak with the statement that at least one of them was white oak. Turns out they are all red oak, and here's my detective work to show that:

First off one of the pieces had a color that looked like red oak but large rays that looked a lot more like white oak. The end grain says it's red oak for sure. Here it is with one of the long rays circled.

I then looked at the end grain of all 4 and found that they are all red. Because of the sanding process that I use, the large pores of oak get clogged up with sawdust and it can be very hard to tell if the pores are open (red) or closed with tyloses (white), but if you look carefully you can tell the difference.

First here's the end grain of the red oak piece above plus a second piece that is so obviously red (open pores) that I didn't bother with sanding the end grain.

Here are the other two pieces. They both show a fair number of open pores but the real trick is telling the clogged ones from the tyloses in white oak.

If you look closely at the clogged pores above, you'll see that they generally look like smooth blobs. That indicates sawdust. Below are a couple of white oak end grains for comparison. As you can see if you look closely, you'll see a few open pores (that does happen in white oak) but most of the pores are closed and instead of looking like smooth blobs of sawdust, they have the look of a little glass pane that's been broken and then glued back together --- that's the look of the tyloses which indicates white oak.