Lacquer thinner is lacquer thinner, right?

I wish I had a nickel for every time I have heard those words either as a rhetorical question or a bold statement of fact. In the 21st Century when lacquer coatings are very high tech, the answer is almost always a resounding no. But before we can understand why this statement is not true, we need to look at this “chemical stew” known as lacquer thinner and understand what makes it what it is.

Yes, those liquids described as lacquer thinner are made up of a number of different chemicals. Those chemicals fall into two broad categories; diluent solvents and active solvents. Both have a function that is described by their name. Diluent solvents are there to dilute the nitrocellulose and/or resins. To illustrate why dilution is important, nitrocellulose, as it arrives from the manufacturer, resembles a barrel of the lint that comes out of your clothes dryer. The diluent turns that into a liquid. Active solvents are there to actively help that liquefied combination move from the spray tip to its “forever home” on the wood and get it to lay down into a glass smooth film.

A Proper Mix
Let’s examine what’s in a pail of lacquer. It contains two things: volatiles and volume solids. The volume solids (the nitrocellulose and/or resins) are what you pay for. Yes, you pay for the volatiles too but understand that by the time that coating is sprayed out and cured, all of those volatiles have flashed off into the atmosphere. All that you have left on the surface after the lacquer has cured are the volume solids. As volatiles, the diluents and actives have gone away and the resins remain.

 Lacquer Pail a Chemical Stew
Photo: Marshall Furniture
• Stick to solvents made by the coatings company that makes your lacquer.
They have all been tested and will work well with them.
• If you need a slower or a faster solvent, ask a coatings rep for his

Know What’s In Your Lacquer Thinners
• Stay away from reclaimed lacquer thinner. You never know what is really
in them and neither does the reclaimer.
• Unhappy solids tend to turn to cottage cheese. (Wrong diluents and/or
actives make the resins solidify and clump.)
• On a hot day, add all the fast evaporating active solvent that you want
but it may not help you a bit. The solvent may well be gone before the
coating hits the surface. The results are such things as orange peel, over
spray, or dry spray.
• Less is more with evaporative speed of an active solvent. Remember,
lacquer thinner is a chemical stew. — B.B.

These 21st century resins and coatings are wonderful in what they can achieve for us. Yet, they also demand respect. When you open a brand new pail of lacquer, I can assure you that the manufacturer has mixed the proper solvents (the volatiles) in with the volume solids (the film-forming resins) to keep all those molecules in that pail as happy as possible and ready to do their job for you. You can also be assured that their lacquer thinners are designed to work the best with their resin packages. But the journey from the pail to cured coating is a difficult and sometimes perilous one. Along the way, that coating is exposed to temperature, humidity, air flow, differences in spray equipment, and differences in the sprayer’s gun technique. Then too, let’s not forget that lacquer is often affected by the surface it is applied to. Is it an oily wood, solid wood, veneer, stained surface, dyed surface, sealed surface, scuffed surface, etc? As you can see, it might not take much to make that coating wish it was still back in its pail.
One thing that is true in almost all of those cases, there is a chemical cause or effect to each of those issues. Some may compel us to add a little “lacquer thinner” to the mix to overcome the effects of a hot day, a lot of airflow over the surface, or a gun that doesn’t atomize well.

If all lacquer thinners were the same, adding a little bit more would be easy. But, it’s not. As most folks who use coatings in metropolitan southern California know, most of the solvents in regular lacquer thinner are off limits by air quality regulations. For the rest of us, we have a whole list of solvents to choose from that are either diluent or active.

Here’s where it gets tricky. I didn’t take chemistry and I’ll bet that most of the folks who spray probably didn’t either. But the answers come down to playing the part of smart chemist or mad chemist. Being in the second category can certainly cause harm on occasion. Don’t worry, I wouldn’t suggest signing up for chemistry at the local community college yet. Just think about these simple things. Until next time…spray on!!!

Bernie Bottens ( writes and teaches on the subject of wood finishing in industrial woodworking. Based in Portland, OR, he is a Wood Finishing Specialistwith Louis and Co., and teaches wood finishing to shop owners, shop foremen, spray technicians and finishers all over the Pacific Northwest. Bernie is also the owner of Kapellmeister Enterprises Inc. He can be reached at [email protected].

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