Q. Our glued panels normally have a wonderful surface that is smooth, hard, and finishes to a premium product. However, once in a great while, we will find a small area that seems to have microscopic fuzz. With today’s thin finishes, we see these areas as not meeting our quality. What should we do, if anything, to correct this?

A. I know exactly what you were referring to, and there is an easy cure. We have a technical name in the wood business for this issue called tension wood. 

Tension wood is formed in all the living trees of hardwood species, especially cottonwood, yellow poplar, and even red oak.
Tension wood is formed in the living tree due to various causes including stress from outside that often causes a curved stem. 
Tension wood is also formed around the larger knots. 

Simplified, the miniature, skinny soda straws that we call cells form the product we call wood are made of two main chemicals — cellulose (cotton essentially) and lignin (the strength-giving component that also glues the cells together). 

When tension wood is formed in the tree, the result is that there is much more cellulose and much less lignin. So, the tension wood cell is rather weak. This weakness shows up in the surface when we machine or sand it. The week cells are easy to push over rather than cut, especially when the cutting tool is dull.

When machining tension wood, it is critical that we have sharp tools obviously. This includes sharp sandpaper as the minerals in the sandpaper do get dull. With that dullness often comes a little more pressure, which again pushes the tension wood fibers into the surface rather than cutting them off.

The simple solution is to use sharp sandpaper, which translates into using fresh sandpaper, rather than using sandpaper until it gets quite dull. 

I have also heard of using sanding sealer before final sanding, which stiffens the tension wood cells so they can be cut easier.
Although sharp sandpaper sounds rather simple, there is no simple way other than experience to determine or know when sandpaper needs to be changed. 

However, when looking at sandpaper if you think it needs to be changed, it probably needed to be changed a while ago. What I’m trying to say is that most of us use sandpaper beyond its useful life.

One other comment about tension wood: With more cellulose in the wood cells, they become somewhat more absorptive of finishes. 

This extra absorptivity can create a slight difference in appearance in the finish. A finishing expert will have to work with you if this difference in appearance is an issue.

Q. I am one of the managers of our plant and all the neighbors think that I should know everything about wood. So, a neighbor is putting in a decorative fence and wants to know species, treatments, and so on. Can you give me a quick overview, even though the topic is a bit far from the FDMC main line?

A. I can appreciate your dilemma. Here is a really short overview that I hope will help. 

It is important to understand that a security fence or fence to keep the cows off the highway would have different answers than for a decorative fence.

There are three parts to a fence, the posts, the frame,  and the staves.

POSTS. In my opinion, in most of the US east of the Rocky Mountains, properly treated southern pine posts, usually 4” x 4” are the preferred posts. They should easily last 30 years and require minimal maintenance. 

The chemical treatments used provide protection beyond what is naturally available in the cedars, and several other commonly used species, including black locust. And in some parts of the country, we might find a local pine or other softwood species used as posts providing reasonable service ability. (With some species, we are finding that trees harvested 50 years ago have more natural protection than trees cut today. So, be careful when referencing historical data or stories.)

FRAME. The frame must be durable, as maintenance or replacement can be quite expensive. For that reason, I prefer using properly treated southern pine. 

Again, some local species that are treated can provide reasonable durability. You may decide that a 30 year fence is too expensive and unnecessary; this means that many different species could be used. The riskiest part of a frame is the ends of the pieces which can trap water and stay wet long after rainfall. 

This increases the decay risk for the ends. When framing members are freshly cut, that does not provide as much protection as a factory cut that was then treated. So freshly cut ends when assembling the fence should be treated on-site to enhance their decay resistance. In any case, the framing should be as far from the ground as reasonable to enhance drying after rain. Pruning of shrubbery close to or in contact with the fence is prudent.

STAVES. Although I do not have any published numbers, I suspect that cedar is the most common species. Actually, there are at least six wood species that we call cedar, including western red cedar, the traditional stave material. 

I personally believe it is prudent to make sure the bottom of the stave has at least 3 inches of clearance with the ground so that grasses and weeds can be trimmed. The resulting air circulation will help dry the stave ends after rain. Remember to use non-rusting fasteners. Also, remember to get, an extra supply of staves to assist in rapid, similar looking, repair staves. 

I also believe it is prudent to use a penetrating stain rather than a film forming finish on the fence staves. Whenever possible, a water repellent is helpful in reducing the risk of deterioration.

I hope this info helps you and your neighbors.