Since I started milling lumber, determining the difference between red oak and white oak has been a challenge. I’ve got a good handle on it now, but there are plenty of times (at least once a week) when a customer has a piece of wood that they want to identify. It is usually some old barn lumber and usually some sort of oak.
I have had a lot of practice trying to figure out what kind of oak I am dealing with since many of the logs I cut are salvaged. Often they are old, without leaves or even bark, and a challenge to identify. Even just raw, newly planed oak lumber can sometimes be tricky. The secrets lie within the structure of the wood itself.
What about color? Color can help, but it can also be misleading. While white oak is less red in color, red oak can range from very red/pink to the exact same color as white oak. I use color as an indicator only if the board is very red, which most likely makes it red oak. Anything in the tan range needs to be investigated further. Note that newly cut white oak lumber turns a bright pink when exposed to the air and then goes back to tan after drying (read more about that by clicking here).
How about the grain? The grain or texture of oaks is very similar. Even when finished, both just look like oak. There are subtle differences, but if you only have one oak in front of you and you aren’t sure what it is, it still just looks like oak. White oak is, on average, a finer texture, with tighter growth rings and a more refined appearance, but there are plenty of red oaks out there with tight growth rings that look similar. Red oak as a family has several members that are fast growing like shingle oaks, willow oaks, laurel oaks and pin oaks, while all white oaks are usually slower growing. If you find an oak board with wide growth rings and a coarse appearance there is a good chance it is a red oak.
Isn’t white oak water tight? Now, we are on to something. White oak, as compared to red oak, is water tight and is used to make wine and whiskey barrels. White oak can hold water because the “open” pores are filled with tyloses, which looks like foam – red oak is not. If you look closely at the pores on an oak board (and your vision is good) you will be able to see grain that either has open pores or pores that are filled with tyloses. On a very small level, especially with a magnifying glass, you can see the difference, and it is usually very clear.
How about the rays? Finally, we’ve got it. The big difference is in the rays. White oak has long, showy rays, which are especially visible in quarter sawn lumber and give quarter sawn white oak it’s one-of-a-kind appearance. However, the rays are also visible on flat sawn lumber, which is the main way that I discern between red and white oak. On the face of flatsawn red oak lumber the rays look like little short tick marks, usually no longer than 1/2″ long. The marks are very visible and strongly contrast with the surrounding wood. White oak has long rays, and on flat sawn lumber the rays look more like straw. The rays are so long that they blend together and are often hard to tell apart. There may be a few shorter ones here and there, but on average the rays are well over 1/2″ long.
The main reason it is necessary to discern between red and white oak, besides general appearance, is to determine its durability. White oak is water-tight and great to use both indoors and outdoors. Red oak is more like a sponge. It will tend to soak up water when it can and quickly rot. Red oak can be used outdoors in vertical applications, like barn siding, and last for quite a long time, but in horizontal applications, especially where the wood will dry out slowly or not at all, it wouldn’t be uncommon for red oak to decay in just a season or two. My unofficial testing of both species used in my own garden for tomato stakes showed a major difference between the two species with red oak rotting and breaking off at ground level in just one summer/fall season, while the white oak showed no symptoms.
The good news is that while it may be difficult at first to tell the difference between red and white oak, it isn’t impossible and actually pretty simple if you look in the right places. Remember you can check out the color, gawk at the grain and peek at the pores. And, if all that doesn’t work, you can always just rely on the rays.