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 Post subject: David Marks Tips
PostPosted: Mon Nov 18, 2013 8:44 pm 
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Joined: Fri Feb 06, 2004 1:24 pm
Posts: 1570
Location: Saline, MI
These writings are published here courtesy of Dennis and David Marks.

David Marks Oil Mix

What is the mix ratio for the Linseed Oil, Tung Oil, and Urethane?

I have tried various methods of mixing linseed oil and tung oil in the past, but since the mid 80's I've been using a product called Seal-A-Cell and Arm-R-Seal made by the General Finishes Company and available through mail order as well as from Woodcraft.

Since doing the first six seasons of Woodworks, this finish has been improved and no longer has the make-up stated in the show. I use two products starting with a sealer and finishing with a top coat. Company representatives state the sealer (which is clear but also available in different colored stains) is a blend of modified linseed oil, oil modified urethane, and alkyd resin, and dryers. The topcoat I use is called Arm-R-Seal and is now an oil modified urethane with dryers. The Arm-R-Seal is available in gloss, semi gloss, and satin.

A high quality finish starts with good surface preparation. This means thoroughly sanding the surface with 220 grit sandpaper or higher. I usually sand to 320 grit to bring out the clarity of the grain. Because of the time limitations of the show, we generally don't demonstrate much sanding. After removing the dust (I use compressed air, if you don't have compressed air, a vacuum cleaner and tack rags work well), I apply the first coat of sealer liberally to the surface allowing it to soak in for a few minutes and then use some soft rags and buff off all of the excess. This is important otherwise you will have resins that get sticky and leave an uneven surface. I let this coat dry overnight preferably at 70 degrees or warmer. A cold and damp environment can cause a finish to lack clarity and delay drying time.

The next day I thoroughly buff the entire surface (including the backs and bottoms of furniture which I finish to balance the piece and maintain equilibrium with 4 OT (0000) steel wool. This is the finest grade and I find that it really smoothes the surface. After removing the steel wool dust, I apply the first coat of Arm-R-Seal gloss. As a rule I always build the finish with coats of gloss whether it is oil, lacquer, urethane, etc. Then, if I want a semi gloss or satin sheen, I'll use that for the last 1 or 2 coats. Keep in mind that the Arm-R-Seal dries faster so I usually just work smaller areas up to 12 square inches and overlap the finish. Again, I brush it on, let it soak in for a minute and rub the surface dry with a clear cloth. Let it dry and repeat the process. I find that a total (including the sealer coat) of 4 or 5 coats usually creates a nice smooth finish that protects the wood while bringing out the beauty and depth of the grain patterns.

FINISHING FURNITURE

The finish is usually the last thing that you do when building a piece of furniture, but it is the first thing that someone sees when looking at your work. You can do a great job designing and building a piece of furniture, but if the finish is of poor quality it will devalue the entire piece. Finishes can be divided into two main categories: air oxidizing finishes and solvent release finishes. Air oxidizing finishes cure by reacting with oxygen and this category includes oils, varnishes, and urethanes. Solvent release finishes cure when the solvents evaporate into the air, leaving a layer of resin on the surface. Finishes in this category include shellac, lacquer, and some water based finishes.

No matter which type of finish you select, keep in mind that approximately 60% to 70% of a good finish is surface preparation. That means scraping and sanding until all saw marks, mill marks, etc, are removed. Tabletops are the most critical and need to be examined in raking light. That means placing a light source near the table and positioning yourself so that you can see the light reflect off the top. As you move around, your eyes should be able to scrutinize every square inch of the top, revealing any scratches, flaws, high spots, or low spots.

Generally speaking, I prefer a hand rubbed oil finish for most of the furniture that I build. Linseed oil and Tung oil are the two most commonly used oils in finishes and both of them have withstood the test of time. Linseed oil is derived from the flax plant and has been used since the ancient Egyptians. Tung oil is derived from the nuts of the Tung tree which grows in the Far East and was used to help preserve the Great Wall of China. Both of these oils penetrate the structure of wood cells creating a finish that is “in' the wood as opposed to being “on' the wood. Applying multiple thin coats will create depth and accentuate the figure of the wood.

Oil finishes do not offer the same resistance to moisture that film finishes like lacquer and polyurethane do, but the trade off is that they allow for a very natural looking finish and permit you to experience the tactile quality of the wood. In addition, they are easy to repair. If the surface looks wom, you do not have to strip it and sand it; you simply rub in another coat of oil. I have also found that they can be enhanced by lightly rubbing with 0000 steel wool and applying a light coat of wax.

INLAY

The art of inlay can be traced back 4,000 years or more to the ancient Egyptians. Throughout history, inlay has graced a wide variety of wooden objects from picture frames to furniture and accessories, to musical instruments. Inlay can also be found in most cultures but the French and Italians are recognized as the preeminent masters of this art form.

The technique itself is actually not that difficult. however it does take time, so it is helpful to be a patient person. I like to work with materials that are approximately an eighth of an inch thick. I begin by drawing a picture of the artwork. If drawing is not one of your strong points, don't worry, there are plenty of books (Dover publishes many) that have artwork that is legal to copy. You can use tracing paper to copy the image and then make photo copies to use for your project. After selecting the woods that I think will best express the feel of the piece, I take the stock to the band saw and resaw it to an eighth of an inch.

To ensure the correct placement of the design, I place a photo copy of my artwork in the location that I want and tape one side of it so -that it doesn't slide. Next, I slip a piece of carbon paper underneath and trace it onto the stock. The next step is to number the individual pieces in the order in which they will be placed. This is important if one piece overlaps another and you need to be certain which piece gets inlaid before another goes over it. After that, I cut out the individual pieces of the photo copied design and glue them to the various pieces of wood. I use a little yellow glue to bond the paper to the wood. Once the glue has dried, I use a scroll saw with a fine toothed blade to cut out the pieces. Keep in mind that you will need to cut some areas oversize where the boundary of the next inlay overlaps them. This, will give you some extra material to get a tight fit. The key to getting a tight fitting inlay is to accurately define the margins. The way that I accomplish this is to start by using some double stick tape to attach the piece to the stock. Once it is secure, I use a sharp exacto knife and scribe around the perimeter. It is best to start off lightly and scribe all the way around and then add some pressure and scribe once or twice again. If you start offwith too much pressure, your knife might track on some grain and move away from your intended boundary. Next up, take a putty knife and pry the inlay piece loose, remove the tape and take a fine pencil point and darken the scribe lines. Use a router with an eighth inch or sixteenth inch carbide bit to rout out the background. As you meticulously rout along the borders you will find that the scribing severed the fibers of the wood and you will see some fibers curl up and fall off indicating that you have reached the boundary line. Use a sharp chisel and a knife to remove smaller areas. After lightly chambering the underside of the inlay to ease the fit, I apply some yellow glue and clamp it in. Once the glue dries, I use a sharp scraper to level it. Inlay is a great way to express your artistry and add a higher level of value to your work.

SHARPENING SCRAPERS

Scrapers are one of my favorite hand tools and I find them to be indispensable in the woodshop. They are made from thin pieces of steel, and come in a variety of sizes, shapes, and thicknesses. The one that most people are familiar with is the rectangular scraper that is approximately 2-1/2” by 5”by 1/32”. The challenge that many woodworkers have with scrapers is learning how to sharpen them properly so that the scrapers remove shavings as opposed to simply producing sawdust. The following is a description of how I like to sharpen my scrapers.

The first step is to file the two long edges. Clamp the scraper in a vise and use a single-cut mill file to flatten the edges. Start by holding the length of the file parallel to the length of the scraper and then angle it approximately 20 degrees or so. As you draw the file across this will help the metal filings to clear. The goal is to create a straight edge that is 90 degrees in the cross section. In talking to many woodworkers, I have found that after filing the edge they go to the burnisher to raise a burr. The problem that they encounter is the burr does not last long or that it does not cut nice shavings. The reason for this is that the file leaves a series of microscopic serrations in the edge. The method I use involves a further investment of time, but it definitely pays dividends in the results; shavings as opposed to simply sawdust. After filing, I use Japanese water stones to polish the sides and edges of the scraper. I start with the coarse 800 grit stone then I go the 1200 grit stone, and I finish with the 6000 grit stone. Polishing the sides is fairly straightforward. Lay the scraper flat on its side and use downward finger pressure to hold it flat on the stone as you work it back and forth. Polishing the two long edges is more challenging. The difficulty is in holding the scraper vertically on the stones. If you rock it you will round the 90 degree comers and it will not cut. My simple solution is to use a block of wood milled to 90 degrees to support the scraper. I find this works well and does not damage the stones. Be sure to work the scraper diagonally to spread the wear over the stones.

For buniishing, I like to rub some lightweight honing oil on the scraper and burnisher to reduce friction. Begin by laying the scraper flat on the workbench and hold the burnisher a few degrees off horizontal as you stroke it. This preparatory stage is called raising the burr. Next, I hold the scraper in one hand and the burnisher in the other so that it is approximately 5 degrees down from horizontal and approximately 5 degrees forward from perpendicular to the scraper. Using moderate pressure I draw the burnisher across the scraper about ten times. At this time I usually have a fine burr that cuts quite well. I find that I can reburnish the edge as needed almost a dozen times before having to go back to the files and stones.

_________________
Things should be made as simple as possible, but not any simpler. -- Albert Einstein
Vision without action is a daydream. Action without vision is a nightmare. -- Japanese Proverb


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