The term “penetrating finish” is one of the most misleading in the vocabulary of finishing because all finishes penetrate. The term is generally used to describe just oil finishes, which dry slowly so they may penetrate a little deeper than faster-drying finishes. But depth of penetration doesn’t have anything to do with protection for the wood, and it’s here that the term becomes misleading because many people think it does, and some manufacturers claim it does. The common descriptive phrase is that the finish “protects the wood from the inside.”
But the quality of a finish that creates better protection for the wood—that is, protection from moisture getting into the wood—is that it dries hard so it can be built thicker on the wood. The thicker the finish, within limits, the better it resists moisture penetration, and oil finishes can’t be built up because they don’t dry hard.
The better terms to use are “film-building” to refer to finishes that dry hard so they can be built up, and “non-film-building” to refer to finishes that don’t cure hard enough to be built up. Using these terms, oil finishes, and also wax finishes, are non-film-building finishes. Varnish, lacquer, shellac and water-based finishes are all film-building finishes.
It seems that one of the topics I get a tremendous amount of emails about is when folks are having issues due to the heat and humidity. A huge number of woodworkers spray their finishes outside and in doing so, are at the mercy of uncontrolled temperatures. Spraying in these conditions can be risky business.
Most finishes simply do not like to be force dried. When spraying in direct
sunlight the surface of the finish will skim over leaving the underlying finish still soft. The finish can then blister; this is most predominant in solvent base finishes. The surface dries and the air that is trapped in the pores of the wood cannot readily escape.
As the air rises it must now break through the dried film and forms a blister. It is a situation where the direct sunlight is the culprit and being able to shade the surface makes a huge difference.
Another issue as a result of the surface drying rapidly is called “blushing”, particularly in hot humid areas. Again, the moisture is trapped within the finish as with blistering. The solution once again is to shade the surface from direct sunlight. If using compressed air, make sure your air is dry and filtered. Turbine systems are the best solution to ensuring clean dryer air.
Lately, the biggest issue is being able to wipe on any non-oil dye or stain in hot/humid weather. Oil-based stains, because they dry so slowly, are usually not an issue. Gel stains, because of their heavier viscosity, dry quite rapidly. Water base stains and dyes can be very problematic. Alcohol/Lacquer dyes and stains can be all but impossible.
Here are a few tips to help when you find your dye/stain drying too rapidly and not allowing you to wipe evenly.
For oil base gel stains, have a cloth damp with mineral spirits ready. Work in as small an area as possible. The objective here is to be able to wipe the stain on and off before it sets. The mineral spirits will help to prevent the stain from drying as fast, but it can also produce a lighter color so often two coats are required. Just be sure to let the first coat dry thoroughly or you run the risk of the second coat softening and pulling off the first coat.
Waterbase dyes and stains can be controlled to some degree the same as the gel stain. Use a dampened applicator which can help, as well as working in as small a section as possible.
In the case of dyes, premixed dyes are not as good as powdered dyes that you mix yourself. Pre-mixed dyes have chemicals that speed the drying process and they are not typically just mixed with water. Powdered dyes that you mix yourself, because it’s simply water, seem to dry slower giving more work time.
We have experimented with utilizing “Floetrol” which is a paint additive used for slowing the drying process in order to improve leveling of water base paints in water base dyes and stains. Floetrol is available at most hardware and box stores where latex paint is sold. We have found it to be very helpful. Our normal mix is approximately 1 ounce to 1 quart of dye or stain. We have used as much as 2 ounces without issue. We have tested this under numerous water base finishes with no issue. But as always, it is a good idea to test any formula on a piece of scrap to ensure total compatibility.
Without question one of the best ways to apply a dye or stain in hot weather is to spray it liberally, again in as small sections as possible, then immediately wipe it back. The spraying allows for a rapid application of the colorant, thus giving more wiping time before it starts to set.
If spraying is not afforded then you want a good stain pad; it will hold more liquid and allow you to cover more area faster. Trying to take a brush or foam brush and apply a colorant in hot weather is all but impossible. The brushes simply do not hold enough material to allow you to evenly wet any sizable area. Just the short time of having to reload the brush is allowing the dye or stain to start to set.
You will also find that using paper towels to wipe off the excess is very
beneficial. They absorb rapidly and allow you to wipe the surface quicker.
To cut to the chase, the bottom line is you have to move quickly before any of the colorants begin to set. It’s not a bad idea to have someone helping you wipe off almost as fast as you wipe on. The general rule of thumb of allowing the dye or stain to set for a few minutes simply put doesn’t work in hot weather.
As stated above, my preferred method is to spray it really wet and start wiping as fast as possible, and in all cases avoid direct sunlight.
If you have ever sprayed the inside of a cabinet with a fast-drying finish such as lacquer or catalyzed lacquer, you have surely experienced dry spray settling on the surface and causing it to feel rough. The bounce back and turbulence created by the force of the spray keeps the finish particles in the air so long that the finish on the surface has already set up before all of the particles land. And when they do land, they stick to the surface, but don’t dissolve in.
The problem is reduced with HVLP and especially with turbine HVLP because there is so much less force creating bounce back. But in the confined space of a cabinet there’s still almost always some dry spray and some roughness.
Minimal dry spray is difficult to show in a picture. But serious dry spray settling on a surface is easy to show, as on the top half of the panel in the accompanying picture.
I’ve often seen instructions to avoid spraying directly into corners in order to avoid the dry spray. Instead, spray the two surfaces that join to form the corner. In other words, make the solution one of spraying technique. But I’ve never found this to work well.
If you think about it, the real cause of the problem is the fast drying of the finish. Slower-drying finishes, such as varnish and water-based finish rarely, if ever, have a dry-spray problem. So the better trick for avoiding dry spray on the insides of cabinets is to slow the drying of the lacquer or catalyzed lacquer by adding a retarder. This keeps the surfaces wet longer, so the dry spray has time to settle and dissolve in, leaving a smooth feel.
You have to be careful, of course, not to retard too much or you’ll have difficulty avoiding runs and sags. So be observant.
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Almost all furniture and woodwork finished between the 1820s and 1920s was finished with shellac. But if you want to test to be sure, here’s the way to do it.
Put a little denatured alcohol on your finger and dab it onto an inconspicuous area of the finish, as shown in the accompanying picture. If the surface gets sticky or if the finish comes off on your finger, the finish is shellac. Shellac dissolves in alcohol, so you could use the alcohol to strip the finish if that is your intention, instead of using paint stripper.
Ghosting occurs when you sand or rub through one layer of finish into the one below, as shown in the accompanying picture.
You can recognize ghosting when the problem area you’re trying to remove keeps getting bigger rather than smaller—like sanding through veneer.
The term ghosting is the traditional name for this phenomenon. As it starts to appear, you see the “ghost” of the finish layer underneath. It is also called “layering,” which describes the phenomenon well, and “witness lines,” a relatively new term, which doesn’t. Nevertheless, it seems that witness lines has become the favored term in many recent wood-finishing articles and books.
Ghosting doesn’t occur with shellac and lacquer finishes because each coat dissolves into the previous one so that all coats become one. Dissolving doesn’t happen with varnishes, including polyurethane varnish, or with most water-based and catalyzed finishes. The separate coats form separate layers that are vulnerable to ghosting.
Sometimes you can disguise ghosting by rubbing with an abrasive such as steel wool. The problem is still there, but the scratches hide it.
The better solution is to apply another coat of finish after you have removed all the problems that caused you to sand deep in the first place. Then level and rub out this new coat without going through it.
The general consensus on figured woods is pretty much saturation, or using a trace coat to further intensify the grain. However sometimes a dye can migrate, meaning it just goes way too dark and can create a blotchy mess.
Broad curl woods like Curly Cherry, Flame Birch, etc. can also absorb any colorant unevenly. We’ve looked at many ways to help control this. I want to emphasize how important it is that you do a test on a scrap before you dive in. With that said one of my favorite tricks is to use water to help control the absorption. I have used our blotch control and thinned it, you have to experiment with this as there is no set rule and a particular wood you’re using will determine how much you need to reduce the blotch control.
Take a look at photo 116. Obviously the side with water is lighter, but when dry, I could do water and another coat of dye. Simply thinning the dye, usually does not work because irrespective of how thin the dye is, it’s going to migrate into the softer grain thus causing it to be darker. The water trick, has proved to be pretty successful and is one of my go-to techniques, especially on figured maples.
Remember the rule “Sneak Up on It” !
If you’ve never had the experience of applying the first coat of finish to a project and having some of the finish fail to “take” because glue has sealed the wood grain underneath, go read something else. What follows is intended for the vast majority of woodworkers who have encountered this problem.
Most often this glue is leftover “squeezeout” (glue squeezed out of joints when they were clamped during assembly). Unless you’re Norm Abrams (who never has squeezeout, but he never has dust in his shop either; doubtless the result of some Faustian bargain), squeezeout is an inevitable consequence of joinery. Unless it’s dealt with properly, it’s almost guaranteed to cause problems during finishing. If a squeezeout problem is first detected at the finishing stage, correcting it is complicated by the fact that fully cured wood glue is harder than the surrounding wood, making sanding, scraping, chiseling, or planing difficult, particularly on inside corners. Sanding away fully cured glue may also result in a high spot where the glue was, and even after the offending glue is removed the finish may not take uniformly.
It’s far easier to deal with squeezeout while the project is in its assembly stage, well before the glue has fully cured. The following hints assume that you’re using a water soluble aliphatic resin emulsion (aka “yellow glue”, such as Titebond II). The materials you’ll need are a supply of glue sticks, clean water, paper towels, scrapers, and a light weight cranked-neck chisel (the bent handle allows the back of the blade to be pressed flush against the wood). The best scraper is a cabinet scraper (more on this below), but it may be necessary to use something smaller in tight spaces. My personal favorite for cramped quarters is a blade measuring about x 2 inches taken from a miniature block plane. Whatever your choices of scraper, make sure they are properly sharpened.
1) Remove the excess sawdust from the material to be glued, but don’t remove it all, and don’t use a tack cloth. Yellow glue has high surface tension. A little dust on the surface won’t affect the strength of the joint, but it will reduce the amount of squeezeout that comes in direct contact with the wood.
2) Apply enough glue to thoroughly wet the joining surfaces, but don’t overdo it. On the other hand, don’t skimp either. The objective is a strong joint, and to achieve this some amount of squeezeout is unavoidable. The difference between dealing with a small amount and a moderate amount of squeezeout isn’t worth worrying about.
3) Assemble the work and clamp as necessary. It’s usually possible to remove the clamps after 45 minutes, which allows adequate time to deal with most squeezeout. But if it’s necessary to leave the work clamped much longer, you’ll need to find a way to work around the clamps. Don’t leave the work clamped overnight and expect to deal successfully with squeezeout the next morning – the glue will be too hard by this point.
4) Inside corners: Since these can’t be effectively sanded once they’re assembled, inside corners should be dealt with as soon as the work is clamped. Use a glue stick to remove the worst of the squeezeout. Keep the stick clean by wiping it frequently on a piece of scrapwood, then on a moist paper towel. When the stick comes up clean, wet the squeezeout area with a clean moist towel. Get the area damp, but don’t soak it. Then use a scraper, getting it all the way into the corner, using firm pressure, and pulling it in the direction of the grain to remove everything that’s left. Wipe the scraper on a moist towel after each swipe. What will come off initially is a mixture of glue, sawdust, moisture, and some fine shavings. After a few swipes only fine shavings will be taken off, and the heat generated by the scraping will have evaporated most of the moisture. You’ll quickly get a feel for when you’ve scraped enough – usually half a dozen swipes is sufficient. Deal with one joint at a time, and work reasonably quickly. It usually takes me just a minute or two to do an inside corner. Due to the glue’s high surface tension, the clock doesn’t really start until you’ve first disturbed the squeezeout, so it doesn’t matter if a joint has sat for a few minutes before you start to work on it. When the work is unclamped, rescrape the area in order to flatten any grain raised by the moisture, get a good light on it, and brush on some paint thinner. If there is any remaining glue (nine times in ten there won’t be), it will show up white. Scrape as necessary until it passes the paint thinner test. Since scraped surfaces may take finish (especially stains) differently than sanded surfaces, hand sand the scraped area using a sanding block with sharp corners and the same grit as the rest of the work. [A cabinet scraper is the ideal tool for removing squeezeout from inside corners. I put the hooks on the short sides of a thin scraper. Short sides so I can apply more pressure, and thin because it gives me a better sense of the underlying wood being scraped. Glue quickly fouls a cabinet scraper, so hooks have to be reformed frequently. You’ll know when it’s time – you’ll get dust, but no fine shavings.]
5) Outside corners on dovetail (or finger) joints: End grain can wick up glue and seal the grain for some distance below the surface, so more material may eventually have to be sanded off the pin piece (the piece with exposed end grain) than the tail piece (which shows only flat grain). If the two pieces start out flush when they’re assembled, the result after final sanding may be a tapered corner. So I make a practice of cutting and assembling dovetails so that the pins (the end grain) stand a couple hundredths of an inch proud of the tails. After the clamps are removed use a cranked-neck chisel held flush to the pins to remove the squeezeout from the exposed end grain. This will also remove most, but not all, the glue from the tails. Don’t worry about what’s left – final sanding will take care of the remaining glue and will automatically sand off more end grain than flat grain. The corner should therefore still be square after all the glue is gone and the joint passes the paint thinner test.
6) Everything else: After the clamps are taken off, use a cranked-neck chisel to get under squeezeout – it should come off as a partially cured ribbon of glue. Use a scraper if necessary, but don’t worry about passing the paint thinner test at this point – any small amount of squeezeout that remains will come off easily during final planing and/or sanding. Make sure the joint passes the paint thinner test when you’re done.
Like most woodworking techniques, all of the above quickly becomes automatic. You’ll soon be able to tell when the glue is gone just by the feel of it, and flunking the paint thinner test will become a rarity. Since I started using this method, I’ve never had a glue problem survive to the final finishing stage. I can’t claim this is the best way to deal with squeezeout, but it’s the best way I know, and it works. Good luck.
Making a decision which furniture care product to use or recommend can seem impossibly confusing if you listen to advertising or read labels. But if you separate the products into four categories for what they do, they are understandable, and you can make an intelligent choice.
The four categories are clear, emulsion (milky white), silicone and wax. A few examples of each are shown, left to right, in the accompanying picture.
Clear polishes are usually packaged in clear plastic containers and are based on petroleum distillates such as mineral spirits or, sometimes, citrus oils. They clean grease and remove wax, but they don’t clean water-soluble dirt such as dried soft-drink spills or sticky fingerprints.
Choose a clear polish if you only want an inexpensive, pleasant-smelling liquid to aid in dust removal.
Emulsion polishes are usually packaged in aerosol sprays and are an emulsion of water and petroleum distillate, which gives them a milky-white coloring when first applied. Their advantage over clear polishes is that they clean both grease and water-soluble dirt.
Choose an emulsion polish if you want a polish that cleans better in addition to aiding in dusting.
Silicone polishes have a small amount of silicone added to a petroleum-distillate (clear) or emulsion (milky-white) carrier. They are usually packaged in aerosol sprays, but Orange Glo and Pledge Orange Oil are exceptions in clear plastic containers. You can identify silicone polishes by the telltale marking they leave when you drag your finger over a surface, even after several days.
Choose a silicone polish if you want long lasting shine and scratch resistance along with a dusting, and sometimes cleaning, aid.
Wax is the most permanent furniture-care product and also the most difficult to apply because of the extra effort required to remove the excess. On deteriorated finishes, wax has the advantage of not highlighting cracking and crazing as liquid polishes do.
Choose a wax polish if you want fairly permanent shine and scratch resistance on old, deteriorated finishes, or on newer finishes without using a silicone polish.
My biggest inspiration is my 8 year old son. He has taught me to teach him that it’s not whether you win or lose,
but how you play the game.
And if you play the game well, you win often.
By Scott Burt
How do we win in the game of fine finishing?
This is a discipline where we tend to drive ourselves to pretty high standards – little room for error.
We start with good habits for efficiency, eliminating all that is irrelevant to the goal – a zen like ritualism in approach. Actually, we don’t start there. That is a level that we work hard to achieve.
First, there is lots of research and trial and error.
Just like you can’t get frustrated with a child for not understanding something that you didn’t explain well enough, you can’t get mad at yourself for not executing a finish you didn’t learn well enough.
In the old days, you could pretty much pull out the sprayer on spray day and make it all fly. That was a different day. Products were more forgiving, open times lasted longer than a summer vacation, and the only thing that really ever changed was the piece you were spraying.
The Triumph of Transfer Efficiency
Sprayers have gotten better over the years. The features, quality of components, systemic nature and performance have advanced immensely. HVLP and air assisted continue to be the benchmarks for most finishers who don’t have time to mess around and want great results that are predictable and duplicable. The machine is rarely the problem, if it’s the right one for your tasks, especially if you set it up for success.
HVLP and air assisted come with a higher cost of entry than airless, but a more hassle free pro level experience. The bottom line is that we can’t get things to lay down like glass when the room is full of mist becoming dry dust, in finish.
So, research, due diligence and self-training, supplemented by learning from other like-minded folks is how we all test our systems for relevance. Remember, failure to adapt is one of the leading causes of finish issues.
This newsletter community continues to grow because good finishers are always looking for, or at least open to ponder, different ways to raise their game. I enjoy being involved because this bunch (readers, writers and publishers) puts its ear right to the ground and listens to many perspectives on finishing and shares the different angles we all need to glimpse the discipline from.
It is the finisher’s challenge to absorb quality info, retain and apply. And reapply, fine tune and commit to long term memory. And reapply. That’s how habit takes root.
The good news is that once something becomes habit, it’s taken over by muscle memory and becomes pleasingly mindless. You don’t have to think much to put your shoes and socks on in the morning, and you shouldn’t have to think much to lay down a good finish either.
If you find yourself having to think too much on finish day, something may be amiss in your program.
Products are the Biggest Moving Target
As above, finding the right products to run in your spray system and gearing yourself to perceive everything in the finishing environment is the nutshell from which to baseline yourself.
If your weakness is creating space for finishing, figure out how to better organize the workshop, and create that dust free finishing shrine. Finishing is a ground up operation. And it is best when portable, not stationary. Caster everything and dedicate a vac and fan.
Once the environment is controlled, half your potential problems are eliminated. Patience and determination make it possible to zero out all other mental interference and focus on getting your finishes right.
At that point, product becomes the biggest variable, so we try to control that too, by choosing products that are user friendly -or, manipulating non-friendly ones to be friendlier.
Consider your Angle
We get a lot of questions through our topcoatreview.com site about sprayers and spraying. It is by far the most popular category.
There are FAQ’s that look like this:
• I have an old single stage HVLP that I haven’t used in years. I want to spray latex primer, will this work?
• I want to spray tinted lacquers, what sprayer should I get.
No matter what stage finish program development you are in, it is mostly a game of haves and wants.
• What do you have for resources?
• What do you want to achieve?
• What do you need to do to bridge the gap between those two things?
These are some points to ponder as you continue to build your finish program. The best finishers never look at any part of the finish game as a chore or inconvenience – just opportunity and challenge. There’s no reward in finish results otherwise.
Explain to yourself why you are doing each step, every time, and explain well so that it becomes habit.
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