- Solid lumber wood with open pores need a filler for blemishes.
- Filler, like putty (but thinner), is made from talc or rottenstone or whiting chalk or pumice or kaolin or brick dust or powdered clay. Paste fillers can be thinned with a paint thinner solvent, usually turpentine. If you're going to apply the filler and the stain together, the stain will be the thinner. The wood filler can be mixed with the desired stain so the staining and filling can be done in one operation. Some paint/hardware dealers sell a type of ready-mixed filler stain for just this purpose.
- It is pigment stained to match (finely powdered resins: lemon-yellow amber, dark forest green & walnut brown). Add a paint thinner solvent, usually turpentine, to moisten it through.
- They can be painted on but, best results will be obtained by rubbing into the surface with a circular motion, especially on cross grain.
- Filler, as putty, will dry slightly lighter than the surrounding wood but, will darken more than the wood when finish is applied.
- Water-based adhesive is used for binding the filler and pigment.
- A wood binding sealant (clear shellac) is used to prevent over darkening by the final finish.
Note: If the filler and stain dry too fast and are difficult to remove, wipe off with coarse steel wool dipped in paint thinner.
There are two types:
- Enamel (cheap, slow drying) primer for enamel paint
- Automobile primer (glossy) for automobile paint
2 parts gum turpentine + 1 part raw linseed oil + (optional) 1/16 part Japan Drier
Prime back sides of wood and out of sight areas to extent possible.
Paint is mixture of a pigment and a binding medium, usually thinned with a solvent to form a liquid vehicle. The term includes lacquer, portland cement paint, printing ink, calcimine, and whitewash. Latex emulsion paint provides such excellent durability and colour retention that it now dominates the paint market. Binder/Sanding Sealer/Sealant keep the powdery pigment together. It also determines the durability, adhesion, cohesion and flexibility of the paint.
Types of Industrial Lacquers Finishes (commonly pyroxylin in an organic solvent, widely used on automobiles and furniture) : Gives intense gloss and hard finish. Unlike varnish, lacquer will melt into the previous layer, providing a very hard yet flexible finish but not all wood is easily treatable with this type of method. Rapid drying, durable but easy discoloration and scratches. It should always be sprayed on using a high-volume, low-pressure (HVLP) sprayer.
- Baked acrylic (synthetic) primer & lacquers (fast drying enamel paints, durable gloss/matte finish): These finishes have recently become popular for industrial products such as automobiles and appliances.
- Water-based lacquers (less toxic and more environmentally friendly) For water paints, pigment is dissolved in a mixture of water with a binder such as glue or casein, or emulsified in a latex polymer.
- Cotton & other Celluloid materials Lacquers finish: Nitrocellulose resin stain is durable & also enhances the grain. It requires no sanding between coats and is soluble in lacquer thinner solvent, usually turpentine.
Clear film- forming (e.g. synthetic resins, varnishes) finishes provide an attractive finish for wood since they allow the natural wood color and grain to show through. Unfortunately, the durability of these finishes on wood under the action of sunlight and moisture is limited. Regardless of the number of coats applied, the film will begin to crack and peel, and the finish will have to be completely removed by sanding or with a varnish remover before a new coat is added.
It contains a wood preservative, a small amount of wax as a water repellent, a resin or drying oil, and a solvent such as turpentine or mineral spirits. The fungicide inhibits surface decay. No finish will block moisture transfer fully; they just slow it down. Penetrating oils provide the least protection. Epoxy offers the greatest moisture blocking.
The common wood preservatives are creosote, pentachlorophenol in oil, and water-borne salts treatments but it is not recommended for use around the home. Its suggested for use as patio decks, outside steps, privacy fences and other home uses.
Mainly in use in India: Dark Walnut or Brown Mahogany colour.
Stains work with the wood, allowing the natural beauty of the wood’s grain to show through. They even allow you to make cheap, uninteresting woods like popular and soft maple resemble higher-quality woods. Applying stain to architectural woodwork or furniture can draw out the wood’s grain, increasing both its beauty and the natural warmth of the wood. Most stains made today are self-sealing. Oil & water creates different colouring of the grain pattern. Staining includes glazing, toning, and shading, all ways of applying a colorant so that you can still see the wood through the colour.
Exterior stains do not require any finish over them, as the stain has additives to protect the wood. However, interior stained wood is almost always finished with a clear finish over the stain. This is most commonly varnish, or a clear PU wood finish.
There are two main ways of defining stains:
- Colorant - is it a pigment or a dye? Some stains contain both pigment and dye.
Unlike pigment particles, dye molecules adhere to the wood on their own. Dye does not require a separate binder to glue it to the wood as pigment does. It only needs a lacquer thinner solvent, usually turpentine, to dissolve itself.
- Binder - is it an oil-, varnish-, lacquer-, or water-based finish?
The binder determines how much time you have to wipe off excess stain. Oil binder cures more slowly than varnish and water-based binders. Lacquer binder cures rapidly.
Stains come in these varieties,
- Aniline dye (needs a lot more skill, toxic as it comes from coal tar, to be mixed with water, alcohol or both but water-soluble is better). Penetrating Oil stains consist of oil soluble dyes, not pigments, dissolved in a synthetic or natural oil-based liquid that penetrates into the wood fibers. Penetrating stains and finishes work nicely on hardwoods because of their beautiful grains.
- Pigment Oil stain or wiping stain (finely powdered resins: lemon-yellow amber, dark forest green (looks brown) & walnut brown. There is also pink, brilliant scarlet, bright green, nigrosine black, dark wine cherry). Because pigmented stains are opaque, they conceal the wood grain pattern more completely than other wood stains such as dye stains. The pigmented oil stain is probably the most popular staining product used for wood refinishing because it is easy to apply. Pigmented stains are very easy to make from scratch. This knowledge comes in handy when you try to match another wood color or when you want a certain wood colour you can’t buy in the store.
- Water-based stains, (tints & waterborne wood binding sealer): It leaves a clean background and defined lines. Water-based stains are gaining in popularity as they are easier to clean, and more environmentally friendly, because the solvent produces less fumes. Water stains can also be purchased in a powdered form which needs to be mixed with water or alcohol.
Anytime water meets wood, there will be a slight rise of the grain, making the surface grain stand up and creating "fuzz." This is called "grain raising." This problem can be greatly reduced by wetting the wood surface before applying the stain, allowing it to dry, and sanding off the raised wood "whiskers" fibers after 30 minutes using fine sandpaper. Be sure to sand only in the direction of the grain of the wood, never diagonally or across it at right angles. Then dust off the surface and proceed with the primer or stain, etc.
- Alkyd / Oil stains: All oil-based stains are for interiors and are more durable. Specific oil types are added in order for the resin to cure when exposed to air. This oil is usually made up of boiled linseed oil, soybean oil or tung oil. Penetrating Oil stains consist of oil soluble dyes, not pigments, dissolved in a synthetic or natural oil-based liquid that penetrates into the wood fibers. Penetrating stains and finishes work nicely on hardwoods because of their beautiful grains.
A linseed 'drying' oil finish is too thin and soft to protect well against heat, stains, or wear. And linseed oil, no matter how you apply it, or how many coats you apply, is quickly and easily penetrated by water and water vapour. So the fact that our predecessors used oil now and then as a finish is no reason for us to use linseed oil. They used linseed oil when they had nothing better. Linseed oil absorbs so much oxygen when it cures that its weight increases as much as 12%.
- Solid/heavy-bodied stains
- Latex-based stains: These are a type of exterior stains for woods which have a natural resistance to rotting, such as cedar, redwood, and cypress. Their colour retention is better than oil-based exterior stains. On the other hand, oil-based stains will take more abuse than latex stains will, so oil based stains are used for wood decks. Exterior stains do not need these finishes, as they have additives in them to protect the finished wood.
When you stain you add colour to the wood so the net result is some combination of the stain colour you've applied, plus the colour that was originally on the wood, and possibly the colour added by the finishing top-coat. For example, a pale blue dye applied to yellow pine might result in a slight green cast. A pre-stain will soak into the wood and allow a more even penetration of the stain. It results in a more consistent and uniform colour. A "Binder" is usually needed to provide durability.
- Use distilled water & mix powder by weight. Add the powder gradually to the hot water (not boiling) while stirring or agitating.
- Wear gloves. Wash Hands thoroughly with soap and water Immediately after use.
When using a power sander for the final sanding, it is best to use a vibratory sander such as a quarter sheet palm sander or a mouse sander. Never use a random orbital sander, as this will put sanding marks across the grain of the wood.
The term staining commonly means applying colour directly to wood. But you can also apply color in between coats of finish. This is called glazing. Or you can add colour to the finish itself and apply it to the wood. This is called shading or toning if you can still see the wood through the coloured finish, and painting if you can't.
Shake or stir the stain thoroughly to fully suspend the pigment. Stain left sitting for as little as four hours will need to be shaken or stirred again. Stain can be applied with many tools: brush, rag, stain pad, cheesecloth, foam brush or some combination, to name a few. The general rule of thumb is to use natural brushes, sometimes referred to as China brushes, for all oil-based finishes (including paint), and synthetic brushes, sometimes referred to as nylon brushes, for latex, acrylic or water-based finishes. Rollers and rags can work for either type of finish. Stain should always be applied with strokes that parallel the wood’s grain. This helps ensure that the stain gets into all the wood’s grain. The stain needs to be brushed out thoroughly, not allowing it to puddle in any part of the wood.
Different woods stain differently, so it is important to test the stain by taking a scrap sample of wood (if available), sanding it to the same degree and in the same way it will be sanded in the project and test the stain and the finish coat on the test piece.
When applying a finish with a brush or roller you may notice some bubbles pop up. Don't panic. Many times these will settle out as the finish dries. If it's a problem, simply use a rag to wipe it down. You can often avoid this by applying a thinner coat. Also, shaking a can of finish will certainly add bubbles, so try stirring instead.
The best conditions to apply are when there is as little dust or other airborne particles as possible. Clean your work area as thoroughly as possible and allow some time for the dust (literally) to settle. Consider using a dust collection system or air purifier.
After the first coat dries, you'll need to either sand it with fine-grit sandpaper (220 grit, no less) or use steel wool. Just be careful not to deeply scratch the finish and certainly do not sand off the finish to the point where you reach raw wood. Wipe off the dust created and apply another coat. Try not to exceed four or five coats of finish.
"The best way to get stains on uniformly is to flood them on liberally and wipe them all off," states Dresdner, "In other words, let the wood absorb what it wants to absorb. Don’t try and use stain as a paint. If you need to do a second coat, that's fine. Let it dry overnight and then do a second coat."
The amount of time which the stain stays on the wood also affects the final color of the wood. Once the stain has soaked into the wood for the desired amount of time, excess stain should be wiped off with a clean cloth. It is important that this time be consistent; the more soak time allowed, the darker the stain will be. Failure to do so will result in uneven colour. Wipe in the direction of the grain, so as to not streak the wood.
Another issue is blotching, that is, uneven dark spots that appear surprisingly and randomly. If your test piece results in blotching, an undercoat of wood conditioner should be applied before the stain goes on. A pre-stain will soak into the wood and allow a more even penetration of the stain. It results in a more consistent and uniform color.
- When sanding, make sure you sand with the grain. If you use a random orbital sander, be aware that you can sand through the outer ply in a flash. Pay close attention to the seam area, because sometimes there is residual glue in that area that will not allow the stain to penetrate. If you want to check for problem areas with glue, you can wet a rag with lacquer thinner and wipe lightly on the shell. There will be a noticeable difference in the sheen of the wood if glue is remaining.
- Avoid sanding the wood too smooth before staining. If you over sand the shell, the pores of the wood are sealed up and stain cannot penetrate the surface. This will result in a very lackluster colour.
- The grain raising problem is solved by using a sanding sealer. The first two coats of topcoat should be treated as the sealer. The goal of sanding the sealer is to 1) smooth the surface of "nibs" to prepare for the topcoat, and 2) NOT sand through the sealer and stain! The goal is not to smooth out orange peel - this will happen later.
Formula: 1 part boiled linseed oil + 1 part white vinegar + 1-3 part turpentine; with old nylon. 24 hours of drying before staining (without sanding).
Sealers are used for several purposes:
- to produce more even staining
- to reduce the quantity of stain absorbed and stop bleeding into bare soft or hard wood;
- on certain areas of wood furniture that tend to absorb too much stain, such as the edges
- to prevent a knot hole from gum-bleeding into the top finish
Industrial Film Finishes or TopCoat
- Resin Lacquers Paint finish (less or no quantity of pigment) refers to other polymers dissolved in volatile organic compounds (VOCs), such as nitrocellulose, and later acrylic compounds dissolved in lacquer thinner
- Lac-based finish: Thin Shellac
- Water-base finish
- conversion (conversion varnish and catalyzed lacquer)
- NC products (nitrocellulose)
- AC products (acid-curing)
- UV Curing products
French chatoyer, meaning "to shine like a cat's eyes," refers to the depth and shimmer that some woods exhibit under the right finish and lighting conditions. Oils that tend to penetrate the wood, along with shellac, oil varnish, and to a lesser degree, lacquer, are all good candidates. French (brown polish) is difficult as it requires weeks of rubbing.
How many people polish their furniture before a dinner party, only to wonder why they are so cranky before the guests arrive? Even worse, the smell of furniture polish can linger on furniture for weeks and months after use, causing a low level of air pollution that puts a strain on the central nervous systems of everyone living there. The petroleum distillates and solvents in commercial furniture polish are highly neurotoxic.
Oil and varnish (including polyurethane) are compatible, so they can be mixed. The resulting finish performs with some of the characteristics of each. But not all mixtures of oil and varnish give the same protection. Some combinations are better than others but you have to find out on your own.
Types of Varnish (finishing TopCoat): Traditionally it is a combination of a drying oil, a resin, and a thinner or solvent. It is added as final step to protect and achieve a film for gloss, over bare wood or wood that has been stained but wears out fast. Some products are marketed as a combined stain and varnish. Enamel paints contain varnish and usually dry to a hard, glossy finish. It also provides natural ultraviolet light protection. Other than acrylic and waterborne types, all varnishes are highly flammable in their liquid state due to the presence of flammable solvents and oils. Spraying is better but more difficult so it is brushed.
Resin varnishes "dry" by evaporation of the solvent and harden almost immediately upon drying. Acrylic and waterborne varnishes "dry" upon evaporation of the water but experience an extended curing period. Oil, polyurethane, and epoxy varnishes remain liquid even after evaporation of the solvent but quickly begin to cure, undergoing successive stages from liquid or syrupy, to gummy, to tacky, to "dry to the touch", to hard.
The amount of thinner used varies. But most common/regular wiping varnishes (including PU) brands has been thinned with 2-3 parts mineral spirits + 1 part varnish. This finish is often sold as oil but is actually a wiping varnish. A blend of straight oil and varnish (including PU). This oil/varnish mixture is often sold as Danish oil.
PU wood (top-)coating (primer, catalysts & finish): It is actually not a type of finish. Instead PU is an ingredient in different types of finishes. It is merely a description of a product containing polyurethane as a resin in the mixture. Its quick drying, low odour and low toxicity. It is soluble in mineral spirits or naphtha.
- water-based PU wood coating: As with shellac, water-based polyurethane gets affected by heat and chemicals, so its not recommended for kitchens, dining, or coffee tables. It dries faster and smells much better than oil-based. Water-based oil-modified polyurethane is a relatively new product that combines the durability of an oil base with the cleanup of a water base. This product can actually be used on wooden floors.
- oil-based PU wood coating: Oil-based polyurethane is slightly more durable than water-based, especially when it comes to handling heat. Its finishes are amber colored and will impart that color to wood, potentially changing the colour of a stain. Oil-based is easier to work with but takes much longer to dry and cure than water-based. When working with oil-based polyurethane, use a respirator in a well-ventilated area.
- Alkyd (oil) varnish: The basic difference between latex and alkyd (oil) is in the binders. Latex paint binds the particles of pigment with a latex such as acrylic or vinyl, while oil paint uses a binder or resin that is derived from a vegetable oil such as linseed or soya bean.
(Both oil- and water-based polyurethane can be applied to latex/acrylic paint; however, oil-based polyurethane will create a yellow or amber hue, especially to light colors. To add durability without affected colour, use a water-based finish.)
The drying of NC-products occurs through evaporation of the solvent. The advantages of NC-products are: short drying time, uncomplicated application and absence of formaldehyde in its contents. The major disadvantages are: low resistance to chemical & mechanical impacts and a low build coating.
Lac-based finish TopCoat: Thin Shellac resin stain is made from combining a secretion from the female lac bug with a solvent such as alcohol. It also comes in solid form or in flakes that must be dissolved and is available in number of colours. Its natural, beautiful as it adds warmth, is scratch and stain resistant but it needs lot of brush work, is less durable and dries too fast which can be difficult if you are not used to applying it. It gets affected by heat so its not recommended for kitchens, dining, or coffee tables. It can also be used as a sealer before applying a stain (to even out the stain’s application).
Amino resins (urea or melamine) and alkyd resins, which are often modified with nitrocellulose, are used as binders for acid-cured materials. Acid-cured materials can have one or two components. An acid hardener should be added to the two-component base before application.
Melamine polish (RFT i.e., running feet for polishing): brand like Cat, sheenlac. In melamine polish, unlike resin lac topcoat, the hardener is not pre-mixed and provided separately. It has to be added separately and quickly applied before it hardens.
They are generally costlier than decorative laminates because they are thin slices of real wood, whereas laminates (such as Sunmica or other brands) are made from paper and plastic resins.