There is a kind of beauty in imperfection.
This quote from cinematographer Conrad Hall can apply to easy woodworking. As with anything else, you will rarely find perfection in wood. Some common wood defects that you should be aware of and know how to work around are mold-damaged wood, bows in the wood, splits or cracks, loose dark knots, and excessive sap residue.
You may find that some wood you have to work with has an unwanted bluish-gray tinge. This is commonly found in woods such as pine, sycamore, and holly. This mold damage is caused by storage in an area that is too warm or not well ventilated. You can solve this problem by using the wood on a part of the project where it will not be seen or by staining the wood darkly.
You may often find a bow in a large plank of wood. This is also caused by a storage problem — one in which moisture was allowed to evaporate. In this case, the best solution is to crosscut the wood into smaller pieces. You may also nail or screw the board into place, but make sure the bulging side is facing out.
Splits and cracks are a result of wood that has been dried too fast. These must be taken seriously because they can not only mar the look of your project but also weaken its structure. You must work around these cracks or cut off and discard the cracked or split sections if possible.
Loose dark knots in the wood are another problem that you may encounter. Dark knots themselves enhance the beauty of the wood but are a problem when they are loose. This looseness is a result of a surface dead branch. The solution here is to glue the knot into place and apply putty to it.
Excessive sap residue is another source of wood damage. It is caused by the tree being injured prior to its cutting. In this case, you should either cut or scrape the residue off and fill the indent in the wood where it was.
One aspect of easy woodworking is being aware of common wood defects and knowing how to work with them. After all, imperfection is always to be expected.