What is the Difference between Red Oak and White Oak?
Oak is often recommended as a boat building material. There are 2 common types of oak where I live, White oak and Red oak. Which is better or can I substitute one for the other?
What is OAK?
Oaks are trees of the genus Quercus which is a member of the beech family Fagaceae. Throughout the world there are over 600 species of oak. There are oak species adapted to most conditions and it can be found in northern as well as southern conditions.
It does not help classification that many oak species can hybridize and produce fertile seeds and trees which are in between species. White oak, among others, commonly does this.
The Genus Quercus is native to the Northern hemisphere and there are many common species, both deciduous and evergreen.
Leaves can come in the common lobed "oak leaf" pattern or can be oval and serrated. Many species have thorny spikes.
A common feature of oak trees is the acorn which hold the seed.
What is Oak used for?
Oak is a hard dense wood that has been used extensively for boatbuilding, as timber for building frames and furniture.
Because some oaks are resistant to fungal attack and insect damage because of high tannin content, the wood can last a long time. It has an attractive grain and has been used as panelling and flooring and decoration in building interiors.
Oak is widely used in barrels and add depth of flavour, aroma and complexity to many boozy drinks. Whiskey, brandy, bourbon many sherries and ports as well as wines are often aged in oak barrels. The species of oak used can influence the flavour so producers have to choose what kind of oak they prefer.
Oak is used in smoking foods. Texas live oak has been used for some of the best BBQ on the planet (my own opinion).
Tannin extracted from oak bark has been a staple leather tanning material for centuries.
Oak gall ink has been one of the most useful writing solutions and makes a strong permanent black ink. It's full colour develops after being exposed to air and some less permanent blue dye is often added to make the ink visible as soon as it goes on paper. Many recipes exist for this kind of ink and it is still available.
To show my age, I was taught to write using metal pen and ink. I come from Northern Quebec and the convent school I went to used this method to teach us to write.
Oak's ability to resist fungal and bacterial attack also makes it a good material for wine corks and cork oaks have been used in many Mediterranean countries to stopper wine and spirits. Portugal has been a major exporter of corks.
Toxicity of Oak Tannin
Leaves, bark and acorns of oak trees contain tannin and are poisonous to humans, cattle, horses, sheep, and goats. The tannic acid causes kidney damage and gastroenteritis. Pigs including the boars and domestic pigs are not affected. There is a long history of pig herds in the British Isles being fed almost entirely on acorns. Pigs in the Mediterranean regions have also relished acorns.
Acorns can be made edible for humans, but they require leaching and soaking to remove the tannins and bitter flavour before they can be eaten.
What is Red Oak
Red oak (Quercus rubra, Quescus borealis) is also known as northern red oak or champion oak. It is a native of North America including South East and central Canada, East and Central US.
It is a fast growing oak and can reach 20 feet in 10 years. They can reach 100 feet with a diameter of trunk of over 6 feet. Trees can live a long time and there are known red oaks which are over 300 years old.
Red Oak readily reproduces with acorns which germinate happily, as long as they don't get eaten!
Read oak is widely harvested and prized for inside and protected used. Wood is strong and attractive.
Like most lumbers the description RED OAK in most lumber store, can include several different species besides the norther red oak. Scarlet oak, eastern black oak, pin oak, shumard oak, southern red oak and other species are often added to the red oak pile.
Red oak heartwood often has a slightly pinky appearance. The sapwood can range from almost white to slightly brown but it rarely pink.
Red Oak is easy to steam bend, glues well and takes a nice finish.
It is readily available and quite good value.
Red Oak is not suitable for lumber used in boatbuilding
Sadly, for boatbuilders this attractive and otherwise useful lumber has a defect that makes it unsuitable for boatbuilding. It has an open structure and the small open capillary tubes can suck in moisture and draw it up several inches into the wood. This open structure make it readily subject to moisture infiltration. Once wet it is hard to dry the lumber and this makes it a victim of rapid decay. Although it has tannin, being wet for long periods make it a victim of fungus and bacterial attack.
This tendency to rot is diminished when the wood is pressure treated. It readily absorbs the treatment because of its open structure. Pressure treated red oak has been used as fence posts and railroad ties and as construction lumber.
It is sometimes possible to see the fairly large pores of the wood.
Red Oak is not very dimensionally stable and will shrink quite a lot.
Because it reacts with iron, screws and other fasteners often stain the wood.
What is White Oak
White Oak (Quercus alba) is a native of North American and can be found in South central and eastern Canada and Central Eastern US as far as Texas.
It can reach 100 feet in height and is noted for spreading over a wide area if grown in the open.
In the spring it goes through a period when the newly emerged leaves are a pinky silver colour which gives the tree a frosty look for a few days.
Fall leaves have a red colour and are sometimes slow in falling.
Because white oak hybridizes with several other oak species, depending on what is growing around, there is some variation as to appearance and habits.
White oak is not mature till about 20 years old and do not produce a lot of acorns before the age of 40-50. Germination of these acorn is not high. It is a quite slow growing tree.
White oak has bark that is sometimes quite light grey in colour hence it's name. The appearance of the wood is somewhat varied. Sapwood sometimes has a light brown to white appearance while heartwood is a greener olive colour.
Like red oak, white oak will stain in the presence of iron. It is also not very dimensionally stable.
White Oak is suitable for boatbuilding
Unlike red oak, white oak produces blockages in the vascular capillaries of the xylem called tyloses. These occur mostly in the heartwood. These effectively limit water flow and close the tubes. This prevents capillary action and greatly reduces moisture penetration and attack by mould and other organisms.
This ability to restrict moisture entry makes the wood less susceptible to decay.
White oak sapwood is not as moisture resistant as heartwood because it has not developed the blocking tyloses.
White Oak is rated as durable and is more resistant to decay than red oak.
It can be steam bent and finishes nicely. In relatively stable conditions it glue well but in boat construction glue joints often fail because of the fairly large dimension changes at it takes in moisture or dries.
Oaks are not very dimensionally stable
Because of this there are sometimes problem gluing oak using epoxy.
Oak has a bad reputation for not being very dimensionally unstable as it will twist and bend and swell as it adjusts to moisture levels. This constant movement is hard on a glue line.
Special more flexible epoxies exist that have proved to be more effective than regular epoxy. G/flex epoxy is an example.
Ash is sometimes suggested as a substitute because it is more dimensionally stable and has many of the qualities of oak.
I have some oak. How can I tell if it's white or red oak
It is hard to tell the 2 varieties apart. It is also possible that it is a completely different oak.
If you place a piece of oak end grain down in a glass of water or better alcohol, the red oak will allow the liquid to rise very quickly up the wood, White oak will get the end wet but the liquid will not be sucked up very high or very quickly.
I don't claim to be an expert in anything. Verify that any material you plan to use is suitable for your purpose. Wood is a natural product that varies a lot depending on growth conditions.US forestry service article on White Oak.