This is the technique I followed (thanks to Jazzdog on TB)
APPLYING A SANDED-IN OIL FINISH
SURFACE PREPARATION AND FINISHING
PUTTIES:
Although it is better to repair a broken or missing piece of wood with a scrap of the same species (preferably from the same board), putties can be used. Three different kinds are marketed:
Oil-Based
Water-Based
Solvent-Based
Putties that use acetone-based solvents will begin to evaporate and harden as soon as the container is opened, despite your best efforts to promptly seal the container immediately after use; acetone is a highly volatile compound with extremely small molecules, and it is a tenacious escape artist -- it will find and escape through any irregularity in the containers seal. Scrupulously cleaning the mating surfaces of the lid and container before resealing the container can help minimize these losses.
Applying a layer of plastic wrap across the top of the can before reinserting the lid can help by acting as an additional barrier to prevent solvent from escaping.
Some manufacturers (e.g., Woodpatch) place the labels on their cans upside-down to encourage consumers to store the product with the lid facing down, which helps thwart solvent evaporation. The instructor adds a small, sacrificial, quantity of acetone to the container before resealing, and stores his cans bottom-side-up. It is also helpful to write the date the can was opened on the bottom of the can with a felt-tip pen.
If a previously-used can of putty has begun to dry out, it can often be rejuvenated if it is still pliable by mixing in additional solvent.
Although putties are best reserved for projects that will be painted, stain-grade projects can include some putty if judiciously applied and finished. In either case, however, it is important to read the labels of both the putty and the finishing products to ensure they are compatible.
A shop-made putty made from same-species sawdust and a few drops of finish (e.g., shellac) can be used in inconspicuous areas, however, the limitations endemic to manufactured putties pertain to shop-made putty as well. Shop-made putties using glue and sawdust are best limited to painted projects.
Putties seldom match the color of the wood to which they are being applied, display completely different texture from the sourroounding wood tissue, and do not absorb stains and finishes the same way the adjacent wood fibers absorb them. Many wood species (e.g., cherry) change color with age, while putties do not. When putty is used in a project that will be stained, oiled, or otherwise remain visible when finished, a bit of camouflage can be achieved using artists brushes, artists colors, and stain, to emulate the coloration and grain patterns of the surrounding wood fibers.
Putty can be difficult to apply without contaminating wood fibers in the area surrounding the repair. These smears will be visible when clear finishes and stains are applied. One technique that can minimize this kind of damage, is to apply blue painters tape before applying putty: When installing moldings that will be face-nailed and puttied, first apply painters tape, then nail through the tape, then apply putty through the hole in the tape. When the tape is removed, the area surrounding the filled nail hole will not have been contaminated by putty smears.
DENTS & CRUSHED FIBERS:
Damage to a work piece during the construction process seems all but inevitable. A dent (compressed wood fibers) can be repaired by applying moisture and heat directly to the dented area, causing the wood fibers to swell and expand to almost their original volume.
Start by lightly scraping the dent and the area immediately surrounding it. Then, apply a few drops of water directly to the dent and allow it to absorb into the wood fibers for a few minutes. Next, dampen a small area of a clean cloth and apply it directly over the dent.
Using a clothes iron set to high, apply heat to the dented area through the moist cloth with the pointed tip of the iron, taking care not to press the iron into the wood. Avoid the temptation to lie the iron flat against the wood -- the objective is not to iron the wood, it is to apply heat and moisture only to the dented area in order to achieve localized swelling of the wood fibers.
The instructor demonstrated this technique by inflicting four dents in a board. He then scraped two, leaving two un-scraped as a control. After circling the dents lightly in pencil, he steamed the dents. Those that had been scraped were virtually invisible, while the un-scraped dents were observable and could be felt.
SCRAPING AND SANDING:
People tend not to notice perfection, but readily notice imperfections: an award-winning project depends as much on the avoidance of conspicuous faults as it does meticulous joinery and application of finishes. When a finish has been successfully applied, people will have an urge to touch your project; to have their sense of touch confirm what their eyes have observed, and to fully appreciate the tactile qualities of the surfaces.
It makes sense for the artisan to employ these same senses during the finishing process. Use your fingers to inspect the prepared surfaces; can you feel defects or irregularities that may be observable when finish is applied? Using an inspection light at an angle to the work piece will cast shadows that will exaggerate surface imperfections; once found, they can be corrected.
One of the most common finishing errors is the failure to completely remove mill marks before finishes are applied; these kinds of imperfections will be magnified when the finish is applied. This is because the scalloped surfaces presented by mill marks expose segments of end-grain which absorb stains and finishes at a different rate than face or edge fibers.
While scraping or planing removes mill marks quickly, leaving a surface that is ready for 200-grit abrasives, the wood fibers are compressed and burnished to some extent (Tangentially, Japanese temple builders maintain their chisels and planes in such a super-sharp state that the wood fibers are compressed and burnished so effectively that water is repelled, making the application of wood finishes unnecessary).
When finishes or stains will be applied, it is important to use abrasives after scraping and planing to prepare the wood fibers to consistently receive the finish. Abrasives cut across the wood fibers, creating a condition in which the wood surface is analogous to myriad wicks, thirstily absorbing stains and finishes, and allowing them to penetrate more-or-less evenly and uniformly.
When water-based stains or finishes are applied, the wood fibers absorb the water swell, and the grain is raised, resulting in a rough surface. Deliberately raising the grain before applying water-based products minimizes this effect. After sanding through 220-grit, apply water to the wood surface and allow it to dry for 24-hours. Then, re-sand with 220-grit abrasive to remove the raised fibers, and apply the water-based product.
A glue size (a solution containing 90% distilled water and 10% hide glue) applied before finishing can serve as a barrier coat that limits the absorption of successive finish layers, and can help reduce uneven absorption exhibited in end-grain and the blotching that can occur when stains are applied to certain species.
OIL FINISHES:
The two oils commonly used in the manufacture of oil finishes are Linseed oil and Tung oil. Linseed oil is derived from the flax seed, while Tung oil is extracted from the nut of a Tung tree. Without further treatment, these oils would dry too slowly to make them suitable as wood finishes.
Metallic driers are added to Linseed oil, which is then heated, resulting in a product commonly known as Boiled Linseed Oil. Tung oil is heat treated to achieve polymerization - a state in which the molecules are bound together in long strands.
In 1989 the A.Q.M.D. (California Air Quality Management District) mandated changes to reduce VOCs (Volatile Organic Compounds) common in many wood finishes. These regulations resulted in the reformulation of many time-tested products that had achieved superior results as wood finishes, and stimulated the inordinate growth of water-based products.
Prior to this time, Watcos Danish Oil products were favored by many woodworkers for their ease of application, short drying times, and superior finishes. The reformulations mandated by the A.Q.M.D. in 1989 yielded products that were generally inferior to pre-89 products and did not dry properly.
After experimenting with many oil finishes in search of a product with characteristics comparable to the venerable Watco Danish Oil, Liberon Finishing Oil (a Tung oil-based product imported from England), was selected as the best oil finish.
Minwax Antique Oil Finish (in the red can) also provides acceptable results, although it does not dry as quickly as Liberon Finishing Oil.
Other Liberon products also work exceptionally well, including their French import Black Bison Clear Fine Paste Wax (available in neutral and several tinted shades), and their steel wool, an un-oiled product that is graded for consistent texture and scratch pattern, and is clearly superior to other steel wool on the market.
NOTE: Steel wool should not be used in conjunction with water-based finishes, as steel particles will become embedded in the finish and will create unsightly black specks in the finish. When using water-based finishes, synthetic abrasive pads are available in several color-coded levels of abrasiveness. Scotch-Brite is one example. While bronze wool will not rust like steel, it is very fragile and disintegrates quickly.
NOTE: An oil finish, while very suitable for the exterior of fine furniture projects, is not recommended for the interiors of cabinets, drawers, et al. Even with ample air circulation, an oil finish will not cure properly, and an unpleasant odor will linger long after the project has been completed.
SPONTANEOUS COMBUSTION:
Before describing the process of applying an oil-based finish, a discussion of spontaneous combustion is warranted. Simply stated, spontaneous combustion describes [oil-soaked] materials bursting into flame: a very dangerous condition that should be avoided at all cost.
Three components are required for combustion:
Fuel
Oxygen
Heat
An oil-soaked rag item provides the fuel, and there is abundant Oxygen in the atmosphere. As oils polymerize, they generate heat. A rag lying flat readily gives off this heat to the atmosphere and combustion temperature is never achieved. However, in a folded rag or wad of steel wool, the heat is not allowed to dissipate -- it is contained in folds and pockets, and the temperature continues to build until combustion is achieved.
Because spontaneous combustion is so likely, and the dangers so severe, caution should be exercised to prevent an occurrence. This is achieved by closely monitoring all oil-contaminated products during use (never leave an oil-saturated applicator unattended), and by promptly disposing of oil-soaked rags, unfolding them and spreading them flat on a concrete or dirt surface, away from all combustion sources, until completely dry.
When the oil has thoroughly dried, you are left with a rag Frisbee that can be safely placed in a trash container.
APPLYING AN OIL FINISH:
Each finishing session will require seven to eight hours when applying a hand-rubbed oil finish; between half-an-hour to an hour to apply and sand-in the oil, followed by six hours of monitoring and surface maintenance. This isnt a project to start at 10:00 p.m. unless you are prepared to be up all night.
Work on only one or two reasonably-sized surfaces at a time - dont attempt to apply the finish to an entire project at once. One of the benefits of an oil finish is that there is no need to finish an entire project at once, or to maintain a wet edge. You can stop and start as you please, as long as you thoroughly remove all slurry before it dries and becomes thick and unworkable.
After sanding to 220-grit, prepare silicon carbide wet-or-dry sandpaper in three grits:
220-grit
320-grit
400-grit
600-grit
Tear or cut the abrasive into sizes that will be convenient and manageable when folded in thirds (I divide sheets of abrasive into eighths).
Youll also need to prepare an ample supply of clean, absorbent, lint-free rags with which residual slurry can be removed.
Wet the wood surface with finishing oil, rubbing it in with your hands until the surface fibers are saturated. The instructor keeps his finishing oil in a squeeze bottle (with an airtight lid), for easier and better-controlled application.
Start with 220-grit and sand the oiled wood, with the grain, until a slurry of oil and sawdust is created. Once a slurry has been created you can sand in circular or figure-eight patterns. Work one small area at a time, until the surface is consistently smooth and the slurry has been packed into the open pores of the wood.
After perhaps ten or fifteen minutes, the surface(s) you have been working will be consistently sanded to 220-grit, and the slurry will have begun to thicken. Now its time to wipe all remaining slurry from the surface of the wood with a clean rag. The instructor uses manicurists orange sticks, wrapped in a clean cloth, to remove all traces of the slurry from corners and areas containing detail and tight radii.
This needs to be accomplished before the product becomes too dry and gummy to remove easily - with Liberon Finishing Oil, you have about twenty minutes. With other oil finishes, such as Minwax Antique Oil Finish, you have a little longer - perhaps three-quarters of an hour.
You will need to monitor your project for bleed-back over the next six hours. Bleed-back is the term used to describe residual oil that will ooze from the wood pores up to the wood surface as the finish polymerizes. Bleed-back will appear as small bumps of finish on the surface of the wood.
Inspect your work once an hour, wiping away bleed-back with a clean rag. Then allow the first coat to dry for 48 hours before proceeding.
When you have sanded the oil finish into the entire surface of the project using 220-grit abrasive, repeat the process with 320-grit. Wait twenty-four hours and repeat the process with 400-grit; after another twenty-four hours and repeat the process with 600-grit. Allow at least seven days for the finish to cure before applying two thin coats of hard paste wax containing Carnauba wax.
Is this still available?
Hi, is the Z4 still for sale
