HVLP for spraying shellac and other finishes

Contactless finishing

Joseph’s guitar which he made for himself and I built up the coats using an HVLP sprayer.

I generally pick my weapons of attack to match the work battles I encounter so I have learned a few things about finishing through the years. There is no doubt that giving a good finish is critical in an age when furniture makers must no only make  but finish too. Just about the time when I had finished my apprenticeship in the 1960s, wood finishing by the masters was coming to a close too. I soon learned that if I couldn’t finish my own pieces, I would soon be out of work.

As a furniture maker I have sprayed different finishes on some production lines starting out in the 1970s when everyone used the conventional cup gun hooked up to any standard air compressor. If you’ve ever sprayed sticks and spindles you’ll know that 90% of the spray goes past the thin sections and out into the biosphere . In those ‘olden’ days, as one of my children once said, it was high air pressure from the compressor and high volumes of the finish you were spraying with. The finish was fine, excellent in fact, but the atmosphere was filled with much more wasting product than should have ever been allowed; bad for health and bad for the environment. We were ignorant back then but we did make progress via a remarkable new piece of kit and change came. A new spray rig powered by a turbine came into being that gave us the high volume we needed using much lower pressure, infinite controllability and freedom from the swirling winds created by the air compressor. Suddenly we were able to put finish exactly where we wanted it in exactly the right proportion. HVLP sprayers were easy to work with and could be adjusted to all but a pin prick in diameter. The were here to stay and the outcome has proven ideal for coating all kinds of pieces with just about any kind of finish, so for water-borne finishes, oil finishes, dyes, stains and water-based paints and also shellac I was a very happy worker of wood.

The importance of spray finishing is basically twofold. It’s fast and, with skill and knowledge, it gives a perfectly even coat in exactly the right measure right where you want it. This translates into good economy of time and money. Because it is brushless, a skilled sprayer can place the finish on in multiple layers and leave a near glass-like finish that often results in a completed work. These gates were sprayed and three coats to a full finish takes only a few minutes per coat. With minor sanding and almost no rub down subsequent to after the first coat, any hand contact is kept to a minimum too.  This is because the grain is not agitated by any brush or contact applicator. The thinned first coat dries and is rubbed down with fine abrasive. Subsequent coats are sealed away by the first coat.  Simple.

 

Imagine brushing on such a finish and how many hours work that would take.

Picking the right water-borne finish can be tricky to get the clarity you need, which nitrocellulose finishes give. I forgot which one I used here but it was very clear.

I sprayed this guitar with a water-borne finish ten years ago. I used a quite pricey Apollo HVLP sprayer I owned back then. Because I don’t make too many pieces to sell nowadays I tend not to spray  for speed so much but more for the ease spraying gives. I usually brush or wipe on finishes on smaller pieces  and that’s what I mostly do if it’s a one off small piece. It’s quiet and easy and I am used to hand applications. If I had 10 tabletops to do, on the other hand, I would most likely spray.

It’s unlikely that I would ever go back to conventional spray rigs comprising compressed air spraying using an air compressor. HVLPs rely on a compact (but noisy) turbine to push air through the cup gun and it’s this that gives the infinite control of volume with low pressure. The low pressure capably lifts the finish from the cup gun to and through the nozzle with surprisingly little pressure and absolute volume control. This reduced pressure disturbs the surrounding air hardly at all so the atmosphere remains for the main part quite calm. A desk and projects like these below can be completed in a matter of just minutes.

Shellac should be sprayed in a warm atmosphere and each coat takes only a few minutes to dry. In an hour a piece can be ready for delivery. I use an Earlex 5500 HVLP sprayer. It’s one of the least expensive but for my level of production it works perfectly. There is no piece of furniture I couldn’t spray with it. When a turbine is going for long periods it is important to have a turbine designed for high volume production.

 

10 comments on “HVLP for spraying shellac and other finishes

  1. Hi Paul,
    I purchased an Earlex 5500 a few months back and have been trying it out on a few pieces – tables mostly. What are your thoughts on spraying oil-baed polyurethane? I’ve been doing this with mixed results. Tends to get sags, but my technique is not great yet.
    I haven’t yet sprayed water-borne polyurethane, but will be giving that a go as well. Something I don’t like about the water-borned poly is lacks the warmth I get with oil. I have considered a first coat of shellac to improve that. What are your thoughts? I also find water-borne lacks the durability of oil-based poly. But that probably is more of a concern for table tops than frames and bases; and on a flat surface I get good results with a quality brush.

    Thanks for all your advise and the great work you are doing bringing hand tool skills back to fore. Thanks to you I’m gradually turning my woodworking hobby into the beginnings of a vocation. A long way to go yet, but it’s getting there. Early retirement plan perhaps.
    Cheers,
    Mike

  2. Even with HVLP, quite a bit of the finish goes into the air. This can be an issue working in a home shop or garage, both for the work and for your work environment. If you are using combustible materials, you really need to do some homework. If you are using noncombustible materials, which pretty much means water borne finishes and water dyes exclusively, the fire and explosion risk is reduced, but you are still aerosolizing a fair bit of material. Having a properly fitted respirator with the correct cartridge for what you are spraying is a requirement. Think about the residual dust from the spray fallout.

    Knowing that I am going to spray a piece changes how I build it. If it is to be sprayed, then drawer bottoms should be removable, boxes and cases should have removable backs / bottoms or it can be hard to spray.

    That all said, spraying leaves a remarkable finish. Don’t underestimate the time required to clean the equipment. Cleanup is another reason why I only spray water borne materials via HVLP.

    • Thankfully I have never needed to spray inside a house but I do know painters that work successfully doing that. Also, I have also sprayed every box large and small box successfully without removing drawer bottoms and backs, Ed. What you describe was the case with compressor driven guns but HVLP solved the s=issues for me.

  3. I’ve been toying with the idea of using HVLP but have never used any spray equipment. One of my concerns is cleaning the equipment. This is never mentioned in reviews. Is that a lengthy job? Do you need to spray solvents through the gun and rinse out the cups between each coat?
    Many thanks

    • Ken, cleanup is one of the rebates features of HVLP spraying. Product is only in the cup and the feed portion of the gun. Fast and easy clean up versus airless. Most HVLP sprayer systems have a cleaning set included.

  4. There are also compressor driven HVLP gun’s that work as well or probably better than any turbine driven unit, but they require a beefy compressor, nowadays there is also LVLP (low volume low pressure) who don’t need as a powerful compressor and share the same transfer efficiency.

    Being a professional finisher I use mostly AAA (air assisted airless) rigs and those are by far the best in terms of transfer efficiency but they are not for small production or hobby use.

    • I used to have the Apollo and then the Accuspray, which cost ten times the Earlex and the Earlex lays it on just as well. My reason for the blog was to encourage people to give other ways a try really.

  5. Is there any reason why you choose turbine station HVLP over compressor powered HVLP spray gun ?

    • No, both work well. Just if you don’t have a good compressor that is a cost factor. A compressor is handy for those who use them. I don’t and a lot of people probably wouldn’t either.

  6. It may be worth mentioning that some finishes are available in cans for brushing or wiping and are also available in spray “rattle cans.” You can build with the brushing or wiping product, and then use the spray can as the very final coat, especially on difficult areas like carvings, to improve the finish. Rattle cans are quite expensive, and they aren’t the best at spraying, but this can be a handy trick to know about at times. Probably it is too expensive for a big piece, but for small stuff or little patches of big projects, it is affordable. It comes to mind because I just did it this morning on something that just wasn’t brushing well. Be aware that rattle cans often use propane or other flammable gasses as propellant, so they are more of a fire risk than what you might think. You still need a respirator with them, but a respirator is cheap compared to the cost of wood and finish.

    I’m glad you’re doing some finishing blogs.

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