Here’s a frequently asked question. Do you really need to clean your spray gun every single time you use it? Do you need to clean it when you go to lunch? What if you are putting it away for a week? Which coatings mean clean “right away?” Here’s the scoop: always clean your gun immediately if you are spraying a quick set up coating such as a two part urethane or epoxy paint.
Clean it even if you are going to lunch. If you are using a pigmented coating and are finished with that color, clean the spray gun. If you are going from a water based coating to a solvent based, or the other way round, clean the spray gun. Other coatings can wait until you are finished for the day. Some finishers keep 2 or more spray guns and dedicate each one to a particular coating, such as water based or solvent, pigmented or clear, 2 part or simple.
Bill Boxer: This week I am going to go over all my spray guns to make sure everything is in order. Here’s what I do:
Here’s how I prepare my spray guns on a regular basis:
- First, I test the spray guns for pattern accuracy to make sure the spray pattern is even from top to bottom.
- If it is heavier on one side or another, I rotate the air cap. If the problem moves to the opposite side, the first thing I do is thoroughly clean the air cap with spray gun cleaner and my cleaning kit brushes. Generally the problem is solved.
- If the problem persists, I look at the nozzle and needle assembly. Again, I clean with my spray gun cleaner and brushes. If that’s not the solution, it’s time to replace the nozzle and needle.
- Next, I lubricate all the threads with Spray Gun Lubricant.
- I check the gaskets and replace if necessary. Then my spray gun is good to go.
- At this time I also make sure I have a supply of cup gaskets, and non return valves.
Nothing is as frustrating as being shut down for such a simple problems.
The vast majority of hobbyist woodworkers, and quite a few professional woodworkers – who might only complete a project or two a month – do their finishing with brush or rag. However, as you begin to undertake more projects, or you move to larger carcass work, it’s natural to start thinking about spray finishing.
There are at least three good reasons for considering a switch to spray finishing. First, it’s surprisingly easy to achieve a near perfect finish with spraying. With practice, you’ll be able to apply the finish evenly and uniformly in a lot less time than you would by brush. Second, because a spray finish goes on thinner than a brushed finish, it dries fairly quickly. Dust doesn’t have much time to contaminate the surface, and you can apply any follow-up coats that much sooner. Third, because spray finishes are fast and easy to apply, you can spend more time building projects rather than finishing them.
A spray finishing system consists of two devices that work in tandem – a continuous source of pressurized air, and a gun that atomizes the finish and delivers it in a controlled pattern onto the work surface. Since the advent of spray finishing, air compressors have provided the necessary source of pressurized air. The compressor forces air at high pressure into the spray gun, which atomizes the finish and projects it at high pressure (upwards of 60 or 70 PSI) onto the work surface. The drawback is that, because of the high pressure, only about 30 percent of the finish lands on the work surface. Most of the finish either bounces back from the surface or ends up sprayed around the work surface. Quite a bit of that wasted finish material ends up vented into the atmosphere.
High Volume Low Pressure (HVLP) systems significantly reduce the problem of over spray and bounce back. They rely on a high volume of air at a low pressure (a maximum of 10 PSI) to transfer upwards of 80 percent of the finish onto the work surface, which is better for your pocket book, and the environment. And, because the air is travelling at a low velocity it’s a lot easier to control the spray.
There are two types of HVLP systems. If you have an air compressor you can purchase an HVLP spray gun that runs off the compressor (these are referred to as ‘conversion spray guns’). Because these spray guns require a lot of air you’ll want to use a compressor in the 5 HP, 60-gallon range, and with an 80 percent or higher duty cycle, otherwise the compressor is going to by constantly cycling on and off.
If you don’t have a compressor, consider purchasing a turbine HVLP. The turbine is somewhat like a mini compressor, except that it delivers a consistent high volume of air at low pressure to the spray gun. Turbines also warm and dry the pressurized air, which helps the applied finish cure more quickly. As well, turbines are very small, so they can be easily stored or moved from one location to another. You’ll find that turbines are rated by the number of fans (called ‘stages’) they contain. The more stages, the greater the volume of air and pressure the turbine can deliver, and the wider the viscosity range of the finish you can use without having to thin the finish.
Ready-to-spray water based finishes are ideal for use with HVLP systems in small shops because, unlike solvent based finishes, they are non-flammable and non-combustible, and they contain fewer environmentally hazardous materials. As well, they’re practically odourless. These finishes have great clarity as they don’t have the typical amber cast that you get with solvent based finishes. And, cleaning up your gear at the end of the finishing session is relatively easy. You do, though, need to pay somewhat more attention to temperature and humidity with water based finishes than you would with solvent based finishes.
Even though water based finishes might be considered ‘friendly’ finishes, you’ll still need to use some kind of spray booth, provide adequate ventilation, and wear an appropriate respirator rated for organic compounds. For small shops, a free-standing knock-down booth is a good choice for spraying large projects. Duct tape pieces of heavy cardboard (appliance boxes work well) or coreplast together for the body of the booth. This makes it easy to quickly set up the booth when needed, and then fold it up and store it between uses. A small, bench top booth is handy when you want to spray smaller pieces. As an alternative to cardboard you could also use plastic sheeting. Set up the booth the night before so that dust has time to settle down before you being spraying. And, for the best results it’s important to illuminate what you’re spraying, so that you can differentiate between wet and dry areas. Instead of overhead lights, use free-standing lights that you can raise, lower, or angle to better illuminate the work. A simple shop made turntable is also invaluable for rotating your work so that you can spray all sides.
If you’re at the point where finishing your projects with a brush is beginning to take too much shop time, then you really should think about spray finishing. A good place to start is one of the better books on the topic, such as “Spray Finishing Made Simple” by Jeff Jewitt, or “Spray Finishing” by Andy Charron. Once you’ve made the plunge, spend the time to get acquainted with the spray system, and practice until you’re satisfied with your results before you commit to a first project. The time you invest in learning about the equipment and practicing with it, will pay huge dividends in the long term.
IWF 2016 is the largest showcase of machinery, supplies and services in the Western Hemisphere for woodworking. There are thousands of products and innovations displayed and demonstrated live. It’s by far the most exciting event for woodworkers. August 25th we are hosting a special guest in our booth #5453.
Master woodworker and television star, Chip Wade will meet and greet, sign autographs, and be photographed with our woodworkers from 10-12pm. Chip has appeared on HGTV’s Curb Appeal, The Block, HGTV’s Showdown, HGTV’s Design Star, HGTV’s Elbow Room, Ellen’s Design Challenge, Oprah, and CNN. Attendees who come to our booth and wish us “Happy Birthday” will receive a free Blow Off Tool.
Directions on cans of paint-and-varnish remover instruct to “neutralize” the stripper as a final step. This is misleading and often leads to finishing problems.
The instruction is misleading because there is nothing in paint strippers that needs to be neutralized. “Neutralizing” refers to acids and bases, not solvents.
What needs to be done with all paint strippers sold in metal cans is remove the wax they contain. Manufacturers add wax to these products to retard evaporation so the stripper remains in contact with the paint or finish longer. This wax will retard the drying and weaken the bonding of most finishes. You should wash off the wax before applying a finish.
Washing is different from neutralizing. Washing means thoroughly wetting and drying off the surface several times. Neutralizing means just wiping over the surface with a damp cloth that is acidic or alkaline.
You can use any number of solvents to wash off the wax residue, but mineral spirits (paint thinner) is the least expensive, stays wet on the surface longer and is just as effective, or even more so, than naphtha, denatured alcohol or lacquer thinner.
Dents and gouges are both flaws in the wood. But they are not the same thing, so they should be repaired differently.
Dents are compressed wood. The wood fibers are still intact, just pressed down or indented. Gouges are also indentations, but the wood fibers have been torn and usually some of the wood has been removed.
Dents can usually be steamed level. Gouges have to be filled with wood putty or some other filling material. Sometimes the indentation is not clearly a dent or gouge, so you can try steaming before resorting to filling.
To steam out a dent, drip some water into the depression using an eyedropper or syringe. If the dent is shallow, the water may swell the wood enough to bring it level with the rest of the surface. If the water doesn’t work, drip some more water into the dent and cover the surface with a dry cloth. Then apply a medium hot iron to the cloth. The hot iron causes the water to turn to steam, which enters the wood and swells it. You can do this several times.
Whether using water or steam, sand the wood well after the moisture has dried out to eliminate any raised grain.
Because water raises the grain of wood, it’s best not to lay a wet cloth on a wide area of the wood, as is often recommended, before heating with the iron, because this will increase the amount of sanding necessary. It’s best to keep the wetted area as small as possible.
This is one of the hallmarks of curb appeal. Nothing pops on the front of your home like a freshly painted front door. And this is another case where brushing is just not so much fun. To tackle this one, carefully pop the hinge pins, and remove the door from the opening. Hang some plastic over the opening just to keep bugs out of the house. Take the door out to the garage and lay it out on sawhorses.
Once again, a quick scuff and vac, and you are ready to fire up the HVLP. As above, select a good waterborne exterior paint. It is best to pick a higher sheen, semi-gloss or gloss, for appearance and durability. And, have fun with color. The front door is a great place to put a little punch of color.
If you do this in the morning, you can have the door back in the opening by the end of the day. Then, crack a cold beverage and gloat. front door photo
Remember, always take a good 20-30 minutes to break down your gun and clean thoroughly. I usually run a bit of warm water through it upon reassembly. Taking that time to pay homage to the gun that just gained you so much free time is good karma for next time you pull the trigger.
Products sold as wood conditioner are washcoats usually made from varnish, though I have seen at least one that is an oil/varnish blend. A washcoat is a finish thinned to five-to-ten percent solids with the appropriate thinner. (Finishes are generally supplied with 20-to-30 percent solids.) In industry, the finish used is usually lacquer thinned with lacquer thinner.
Wood conditioners can be fairly effective on softwoods like the pine shown in the accompanying picture. They aren’t as effective on hardwoods such as cherry.
The purpose of the thinned-finish conditioner is to partially seal the wood, which means to partially stop up the pores so the stain, which can cause a blotchy appearance, can’t penetrate as deeply in those areas that will get darker.
To use a wood conditioner effectively, it’s important to understand that the directions supplied by almost all brands won’t produce good results. These directions say to apply the stain within two hours, which is before a varnish or oil/varnish blend has time to dry. So the stain mixes with the uncured wood conditioner and still blotches.
To use a wood conditioner effectively you have to give it time to completely dry so the stain can’t penetrate. With lacquer this is 30 minutes or so. But with varnish and oil/varnish blend this is overnight, or at least 6 to 8 hours.
To significantly reduce blotching, apply the wood conditioner wet to the surface of the wood and let it completely dry. Then apply the stain and wipe off the excess. But notice from the example that with less stain penetration, the resulting color is also lighter.
I have no idea why manufacturers give directions that don’t work. The only explanation I can think of is that they believe you want to totally complete a project on a Saturday afternoon, and waiting overnight for the wood conditioner to dry won’t accomplish this.
If you engage in the act of finishing at any kind of level, even if just a few meaningful times a year, then you definitely understand that the proof is in the pudding when it comes to creating good finishes. When you get really good at finishing, it almost doesn’t matter whether you are spraying, rolling, brushing, or any combination thereof, the application method is just the medium – the thing standing between you and the result you are after in the finish. The goal is to be able to use whatever means at hand to get the desired result.
Renaissance men in literature were revered for being “skilled in all ways of contending,” and the romantic in me holds the art of finishing to that same standard.
I am lucky to be able to work on all types of interior and exterior finishes and see how they fail, and more importantly, figure out how to fix them. Working on exterior surfaces in the summer gives me the “bulldozer” perspective on finishing. Exterior finishes have to hold up to the elements, which is no small feat. While interior finishes are more Porsche than bulldozer. The sequencing of prep and finishing for exterior trim is not all that different from interior, just different products. But, of course, product drives process. So while similar, everything is different.
Professionally, I am generally either taking finish off or putting it on. Each process comes with a sequence of steps.
What is a finish failure?
On exterior surfaces, it is a finish that literally does not remain intact on the surface. Think flaking or peeling paint. Interior finishes fail in different ways, and it is usually not the fault of the product, but rather the application process. Dramatic interior failures are rare, and more subjective.
If you take finishing seriously enough to continue chasing the dragon of perfection, then you might at times feel like anything short of perfection was a failure, particularly in sprayed finishes.
Number One Cause of Finish Failure…
Without doubt, the biggest way that people create finish failure is by over applying finish: putting too much on at once. It is counterintuitive, I know, and almost like some stubborn vestige of good old fashioned common sense. More paint will hold up better, right? In the old days of old products, sure. And again, it doesn’t matter your particular finishing discipline or interest, the same truths seem to hold.
As products continue to move toward EPA compliance, less is definitely more in the application of finish. Creating thinner layers can really help with adhesion. But can make the glassy lay down you are looking for more elusive – regardless of application tool. In spraying, we refer to the thin coat build technique as “tack coats”. It is easier to get a thin coat of finish to adhere (hold) to a thin layer of itself than to get a heavy coat of the same finish to hang on verticals or edges.
Where Finishes Fail the Most
The number one biggest failure I see in the entire range of paint jobs that failed is the user tendency to apply way too much on the edges of wood surfaces. It is not a conscious decision, it just sort of comes with the lack of control of the application tool and the finish.
It is the “eye” for finishing that I talk so much about. We call them “fat lips” or “fat edges”. On sprayed surfaces, they show up on large surfaces (such as the edges of table tops) as well as narrow surfaces (face frames). They happen both vertically and horizontally.
Side Stepping Failure
Let’s face it, most people don’t really enjoy sanding, and consider finishing a necessary evil at best. I have written in the past in this newsletter about how to trick yourself into learning to love the things you hate about your projects. It is a mind game. The hate of certain aspects of a project is usually rooted in fear. Mastery creates the confidence that eliminates fear.
You are probably expecting me to reveal some esoteric finishing tricks or tips, like some Zen “don’t be there” when failure approaches, but it is really the most incredibly basic practices that create success. Easy to say, harder to do.
Basically, finishing is different every time. And you have to make it the same, by being regimented in everything from your basic habits, to workshop environment and processes. The best finishers I know are highly ritualized, almost instinctual. If something does not look or feel right, they will NOT proceed. Keep in mind, finishes are really only to be appreciated by the tactile and visual senses. It is subjective appeal. Their performance is the only big picture concrete evidence of how you did as the finisher, and believe it or not, that too is detectable by the senses. You can tell when you nailed it. But you have to nail it a few times consistently first.
Here are a couple of habits I notice myself reinforcing in my own work:
- Easing edges - This is where good “edge hold” begins. Breaking, or easing, wood edges is essential to the tactile experience of those who might appreciate your results, and the finish also appreciates having a bit more surface on the edge to hang onto. In a nutshell, those are the reasons to do it. It is detailed work, and has to be done with precision, because those edges define the “lines” that your piece will take, the form. Sometimes just for fun I hack into a maple log with a grinder just to see what form it wants to take. Do this for an hour and you will learn to love the simple act of edge easing as part of your surface preparation ritual on finer pieces of furniture.
- Working from the Edges In – When finishing, whether by brush or sprayer, try focusing on the perimeter of the piece first, then blow down the middle. This is the same mindset for me as a day on the mountain with my snowboard. First couple of runs, I will noodle the edges, then I want to blow right down the middle. Use the whole mountain, with discretion. The finish applied to the edges first helps to “frame” what you will fill in the middle with. Of course, keep it all wet at the same time for uniform laydown.
- Sight it Down - In any phase of finishing (removing undesired finishes, applying new finishes, or scuffing in between coats), always be feeling your surfaces and sighting them down from different angles. In the shop, we use LED inspection lights from all different angles. It is critical to do this constantly so that if you see any issues, you can address them during the limited window of opportunity presented by wet finishes that are trying to lay down.
This is a lot to think about, especially while finishing. That is why it is critical to make them habits, so you don’t have to think about them. It is much more fun when you can just appreciate what is happening at your fingertips.
Plug in some of these habits, even if you already know you should be doing them, and especially if you think you already are.
Secret of Sheen – the Second Coat Is Most Important
The second coat of finish you apply to a project, after you have sanded the first coat smooth, is the most important coat because it provides the depth and sheen. Sometimes you can improve the depth with additional coats, but nothing equals the difference obtained from the first to the second.
Most important in this instruction is that you have to sand the first coat smooth to obtain the full effect. If you don’t sand this coat smooth, the roughness will telegraph through the second coat and reduce the depth and lower the sheen.
The surface will also feel rough. A further point to emphasize is that you can’t ever achieve the full effect of a finish with just one coat, no matter how thick you apply it. This rule holds true for all finishes – even oil finishes.
Spray Pattern Heavier on One Side
A spray pattern, with all the controls on the spray gun wide open, is supposed to be an even, elongated oval shape. If the pattern is heavier on one end than the other, the likely cause is that one or more of the holes in the air cap is plugged up. It’s also possible that the fluid nozzle has been damaged.
To determine which, rotate the air cap one-half turn (180 degrees) and spray again. If the disrupted pattern switches sides, the problem is in the air cap. If the pattern stays the same, the problem is the fluid nozzle.
To clean the air cap, soak it in acetone or lacquer thinner to dissolve or soften the obstructing matter, then blow it out with compressed air if you have it. You can also use very small-diameter picks supplied with spray-gun cleaning kits such as the one offered by TheFinishingStore.com (please link)
Be very careful trying to use a toothpick, because it might break off in the hole and be difficult to remove. Above all, you don’t want to use any metal that might damage the hole.
If you determine that the fluid nozzle has been damaged, you will have to replace it. The fluid nozzle and needle are usually sold in sets.
For those with decks that have spindle rail systems…you would probably rather have root canal than brush those spindles out with stain. (See the above before photo.) Here is another case where a quick scuff and vac gets your ready to roll out the HVLP and save yourself a weekend or two.
Deck stain products are low viscosity (thin) and spray very easily through a good turbine system. They are also available in waterborne formulations these days. Even if you are committed to oil stain, the cleanup will take a few more minutes, but think of the pile of hours you are saving by spraying. While you are at it, spray out any lattice work that you may have on the property. Another case of HVLP to the rescue.
Essentials for Every Woodworker, Novice or Master Woodworker
ECO5 ECO-LOGICAL, ECO-NOMICAL TURBINE SYSTEM Efficient 5 stage turbine
Blow Off Tool In Action
Zhan Viscosity Cup