Planed Finish VS Sandpaper - Microscopic View

[Derek Cohen]

The wood I work is considered challenging, however it has become an everyday event to plane it, and after doing so for 20 years, it is straight forward. Occasionally I use high angled planes still, but mostly I use a chipbreaker to control tearout. Doing so is the easy part of planing.

I still consider the harder part lies with profiling and setting the blade. In this regard it is achieving a desired degree of camber, and the ideal depth of cut, so that the final surface is both flat and that this is achieved efficiently.

I am about to start on a kitchen revamp. This will entail replacing all the cabinet doors and drawer fronts with Rock Maple Shaker frame-and-panel styled doors. There are about 25 doors in all and about 10 drawers. The wood will be finished in a poly varnish, or similar, because this is waterproof.

One of the design issues lies with the panels: they need to be dead flat and not show plane marks. By plane marks I am not referring to tracks, but to the very fine scallops that are created by a cambered blade. These will show up when light rakes across the surfaces. Ordinarily I like this, but it is not a desired feature for this kitchen. Consequently, my plan is to sand the panels. I rarely use a sander, and cannot recall when I last did so, since I would rather scrape than sand with furniture. However I do have a Festo ROS (the name of which is a give away ... what Festool became about 20 years ago), and Abranet sanding disks are magic. The panels will be planed and then finish sanded to 400 grit.

This is not a case of "which is better, planing or sanding?", but one of horses for courses. Reluctantly.

Any thoughts?

Regards from Perth

Derek

[Warren Mickley]

I tend to use stuff like water stains, shellac, oil, and wax. If the surface is fine, you can get away with thin coats.

[Derek Cohen]

Warren, those are the finishes I use as well with furniture. I'd use them in the kitchen if they were waterproof and resistant to heat, steam, etc. I'd rather use a finish I can rub on. I have little experience with spraying, and am happy to keep it that way. Any comments on the durability of the above finishes in a kitchen?

Regards from Perth

Derek

[Stewie Simpson]

If your after a burnished finish similar to what's seen within that video, the hand plane your using for your final pass needs to have a wooden sole. A metal sole wont do it, regardless of how fine you set your shaving. Old school knowledge that wasn't restricted to Japan.

Stewie;

[Stanley Covington]

The video is focused on the skill of the miyadaiku carpenter, and the difference between a planed surface and a sanded surface. It does not touch on finishes. The conclusion the video makes is one sentence: "Sandpaper crushes the wood's cells, whereas planing leaves then cells cleanly cut and whole, rejecting water absorption." So, while the images in the video are instructive, the words are not all that helpful.

We discussed this subject at some length in another thread a couple of weeks ago.

Water beads due to "hydrogen bonding," a phenomenon that causes hydrogen atoms to want to clump together. This phenomenon is absolutely essential to the ability of a tree to suck water from the tips of its roots, through the zylem tissue conduits, and out its leave's surface. Note that water is not forced up the tree, but rather sucked up by negative pressure induced by evaporation of water at the leaves. This works only because of hydrogen bonding, the same force that makes water bead up. It won't happen with alcohol, or lacquer thinner, or any other liquid besides perhaps mercury.

The traditional finish for many woods in Japan, in both exterior and interior environments, is a planed finish with nothing else. So the skill of the carpenter or joiner with his plane is very important.

The expertly planed surface is a proven factor in longevity of wooden structures. Believe it or not, a carefully planed wooden column or beam lasts longer in an exterior location than a painted one (painting is obviously the most durable surface finish available for wood) by a factor of hundreds of years. This is because a painted finish always fails, peels, and powders with time. 30 years max? It must be constantly maintained and replaced. If water soaks quickly and deeply into the a hairy wood's surface, it causes differential expansion and cracking, providing wider paths for water to enter.

In the case of a planed surface, a bead of water is stable enough to span the gaps at the severed zylem conduits. But if the wood's surface is sanded, the hairs penetrate the bead, and will suck water into the grain. Dust collects on a surface regardless of the finish, but it sticks better to a hairy, sanded surface. Dust includes bacteria and mold and mildew and spores that are sucked in with the water, accelerating rot. So it is not an exaggeration to say that sanded surfaces cause the wood to rot relatively quicker.

A sharp blade is an absolute requirement, but beyond 6000 to 8000 grit, it doesn't make much difference in finish. A finer sharpening job does help the blade stay sharper longer. Interestingly, a highly polished blade takes more force to cut wood than a medium sharp blade.

Perhaps more important is an appropriately tight mouth with even pressure by the sole right up to the opening. Most people get this detail wrong. A true sole that doesn't rock is also important. A properly setup and installed chipbreaker is very important when cutting cross-grained wood. But when cutting with the grain, a chipbreaker does not produce a smoother surface than a single blade.

[Stanley Covington]

If your after a burnished finish similar to what's seen within that video, the hand plane your using for your final pass needs to have a wooden sole. A metal sole wont do it, regardless of how fine you set your shaving. Old school knowledge that wasn't restricted to Japan.

Stewie;

A metal plane will do it too.

[Warren Mickley]

Warren, those are the finishes I use as well with furniture. I'd use them in the kitchen if they were waterproof and resistant to heat, steam, etc. I'd rather use a finish I can rub on. I have little experience with spraying, and am happy to keep it that way. Any comments on the durability of the above finishes in a kitchen?

Derek

I would say the durability is somewhat technique dependent. I have a friend who put shellac on his kitchen table. A hot dish carelessly placed with no pad left a mark that had to be restored. However moisture has not been a problem. I have had a small table in the kitchen with shellac for 30 years; there have been lots of cold drinks on it without a problem. Try this: Put a tablespoon of water on a flat finish sample and see what happens over eight hours or so. Also put a sample over a steamy kettle.

One thing to keep in mind is that shellac can be repaired or refreshed a lot more easily than polyurethane.

[Stew Denton]

Hi All,

A few comments, responding to Fred's question, but made with trepidation, as I don't know as much about surface tension as I should. I hope to make a couple of comments of practical application for finishes. (But don't count on it. This may be chemistry filled and boring, so you have been warned and may want to quit reading now while you are ahead.)

That said, this is the 3rd time that I have tried to respond to this post, and the computer ate the first two long, chemistry filled, fiascos, and each try the post has gotten shorter with less chemistry.

To summarize what I wrote before as short as possible with a LOT less explanation as to "why", the water is strongly attracted to the wood surface. This is due to what we chemists call "hydrogen bonding" between the water and "hydroxyl groups" that cover the surface of the wood.

Water has a strong affinity for sugar because of hydrogen boding between the water the many hydroxyl groups on the sugar molecule, and because of that, sugar rapidly dissolves in water. Cellulose is polymerized sugar, it is a big component of wood, and just like the sugar it is made from, has lots of hydroxyl groups and also other oxygen atoms present. All of these are capable of hydrogen bonding with the water, so water loves cellulose, and hence loves wood.

Each water molecule, however, loves every other water molecule too. This is the cause of water's surface tension, which causes the water to form drops, and causes it to bead up, like it did on the right hand picture. The way to overcome the surface tension of the water is to maximize the attraction to something else, in this case the wood surface. Thus, the more surface area that the wood has, the more the water molecules will overcome their love for each other and flow onto the surface of the wood because of the maximized hydrogen bonding with the surface of the wood. This is like it did in the left hand picture.

The cleanly planed wood surface is cleanly sliced off, and leaves a flat clean surface with little roughening of the surface and few fibers. This means a minimized surface area, and thus the attraction of the water to the wood surface is minimized. Because of this minimized attraction to the woods surface, the water stays beaded up.

On the other hand, the sanded surface is relatively roughened, with shredded wood on the surface and many stray fibers. This gives a maximum surface area and thus maximizes the attraction of the water to the wood, and the water spreads out onto the wood surface like it did on the video. The big surface area of the wood overcomes the natural affinity that the water molecules have for each other, thus defeating the surface tension of the water, so the drop collapses and flows into and onto the wood surface.

The effect on finishing is in the following post.

Stew

[Mel Fulks]

Warren is certainly right. Easy enough and legally safe enough for all the modern finish makers to declare shellac too fragile. It was used by US government as a major component of coatings for wooden ship hulls through both world wars.
Fresh shellac is not fragile, in some tests I did ,it took days under water for some white to form on some blocks; after some hours the white clouding disappeared.

[Stewie Simpson]

What is Burnishing?

Burnishing is a finishing technique that is used on wood. It gives the wood a smooth, shiny finish similar to the appearance achieved when using polyurethane or lacquer.

Burnishing is a technique that is frequently used when professionals do not want to apply chemicals to their products. Burnishing is done by rubbing two pieces of wood together. The heat from the friction rubs away soft, dried cell walls and exposes the harder cells. These hard cell walls do not absorb stain or finishes, but they have a glossy sheen that makes finishing products unnecessary. Burnishing can also be done by rubbing small shavings or chips on the wood. Burnishing is often used when professionals do not have time for chemical finishes to dry, but they also use the technique to achieve a certain appearance. Burnishing is used for furniture, cabinets, floors and other items in the house.


Read more: http://www.kitchencabinetkings.com/g...#ixzz4NmVuEHMf

[Stewie Simpson]

If your after a burnished finish similar to what's seen within that video, the hand plane your using for your final pass needs to have a wooden sole. A metal sole wont do it, regardless of how fine you set your shaving. Old school knowledge that wasn't restricted to Japan.

Its a subject I am familiar with;

[Derek Cohen]

I would say the durability is somewhat technique dependent. I have a friend who put shellac on his kitchen table. A hot dish carelessly placed with no pad left a mark that had to be restored. However moisture has not been a problem. I have had a small table in the kitchen with shellac for 30 years; there have been lots of cold drinks on it without a problem. Try this: Put a tablespoon of water on a flat finish sample and see what happens over eight hours or so. Also put a sample over a steamy kettle.

One thing to keep in mind is that shellac can be repaired or refreshed a lot more easily than polyurethane.

Thank you Warren. That is advice I shall follow. I mentioned the choices to my wife. Her comment was, "as long as I can wipe the surfaces down with a wet cloth". I've always like the fact that Shellac is so easily repaired and, although no one is particularly heavy-handed in the family, stuff happens.

I have another related question for all, but will ask it in its own thread.

Regards from Perth

Derek

[Derek Cohen]

Its a subject I am familiar with;

Thant looks like Western Red Cedar to me. Yes? I use it for windows and blinds, not furniture. I finish this with a Sikkens product against the WA sun. Not much need for a burnished finish (unless you mean "burnt" finish ).

I am curious to know what furniture you have made, Stewie. Any photos?

Regards from Perth

Derek

[Stewie Simpson]

Douglas-Fir. Commonly referred to as Oregon pine is Australia. http://www.wood-database.com/douglas-fir/

[Stew Denton]

Hi All,

To those few brave souls who put up with reading the first post.

What is the effect of all of this on finishing.

Well, if this works for water, it ought to work for finishes, right?

Whoa Nelly! There is a fly in the oatmeal. One problem is that water loves the wood surface, so water based finishes will wet the wood surfaces easily. However, many finishes are primarily hydrocarbon based, and hydrocarbons are hydrophobic, that means that are not attracted to water, and it also means that they don't have as strong an affinity for the hydroxyl groups of the wood than water based finishes are. Also, if the wood has not dried well, the water in the wood makes it even less attractive to the hydrocarbon type finishes. Finally hydrocarbon solvents, such as paint thinner, are also hydrophobic, and don't like water. However, if the wood is thoroughly dry, most finishes seem to adhere well.

Well, companies who make finishes do various things to overcome the surface tension of their finishes so they will flow out and "wet" the surface of the wood. I'm sure there are various approaches, but two of the most common are: 1. adding a surfactant to the finish to overcome the surface tension of the finish, which is much like adding soap to water, and 2. reducing the viscosity of the finish by adding solvents or "thinners."

Most older and modern finishes also have some hydrogen bonding capability.

Nitrocellulose based lacquer has a lot of atoms that will yield hydrogen boding and should be attracted to the wood.

Shellac is dissolved in alcohol, and thus must be quite polar and has lots of potential for hydrogen bonding. In addition, the alcohol is capable of hydrogen bonding and will "wet" wood quite well, helping the shellac to adhere strongly to the wood. In addition, the alcohol is very non-viscose, so it acts as both a thinner and a facilitator of hydrogen bonding with the wood.

Drying oils like linseed and tung oil both are fundamentally hydrocarbon based, but the oils have three "ester" linkages in the center of each molecule so can adhere well to wood, and in addition each has multiple double bonds that can crosslink and form very resistant polymers on the wood, in addition to soaking into the wood.

In short, finishes that can adhere to the wood by initially forming hydrogen bonding, and such that can be thinned down easily, without problems, such as shellac should adhere well. In addition shellac can be made with alcohol, and since alcohol likes things like wood and it is very thin, its might be a good choice.


Finally, with some finishes that don't always adhere well, sanding might help, having the wood thoroughly dry, and having the finish that can be thinned down some should help the finish to adhere.

Well, getting too sleepy to write or think. Time to give it up.

Stew