Shellac vs. Lacquer vs. Varnish: What's on Your Wood?

Somebody calls me most weeks with the same knot in their voice. They’ve got a dresser or a table with a bad spot, they’ve watched a video or two, and they want to know if they can fix it themselves or if they’re about to ruin a family piece. Almost every time, my first question back is the same one: what kind of finish is on it? Because the answer changes everything about what you should do next.

Let me give you the short version up front, and then show you how to figure it out yourself.

The quick answer

There are three classic finishes you’ll run into on wood furniture, and here’s the plain-English version of each:

• Shellac is the old one. It’s a natural resin that comes from a bug (the lac bug, over in Asia), dissolved in alcohol. If your piece is from before about 1920, or it has that warm amber glow of a real antique, odds are good it’s shellac. It’s also what sits under a true French polishing job.
• Lacquer is the sprayed one. It came up in the 1920s and 30s and took over factory furniture. Mid-century pieces, most store-bought dressers and cabinets from the last several decades, a lot of that is lacquer. It sprays on fast and dries fast, which is why factories loved it.
• Varnish and polyurethane are the tough ones. These are brush-on (or wipe-on) finishes that cure into a hard, plasticky film. Poly is the modern king of tabletops, kitchen tables, and floors because it shrugs off water, heat, and a coffee cup left sitting overnight.

Here’s why you care: shellac and lacquer can usually be repaired without stripping the whole piece. Varnish and poly usually cannot. That one fact is the difference between an afternoon touch-up and a full refinish.

What each finish actually is

Knowing what each one is tells you how it behaves.

Shellac. It comes from an insect, and it’s been used for hundreds of years. Dissolved in denatured alcohol, brushed or padded on, it dries by the alcohol flashing off. That’s the key trait: it never really stops being soluble in alcohol. Beautiful, warm, easy to repair, but it hates heat and it hates booze. A drink set down on a shellac table leaves a white ring fast. If you’ve got rings, I wrote up how to fix water rings and heat marks on wood tables separately.

Lacquer. Nitrocellulose lacquer sprays on in thin coats, and each new coat partly melts into the one below it. That matters for repairs, because it means the whole finish is one connected layer you can re-flow. It’s harder than shellac and more water-resistant, but it can get brittle and crazed (little cracks all over) as it ages. An old dresser with a finish that looks like cracked pottery is usually lacquer that’s had a long life.

Varnish and polyurethane. These cure by a chemical reaction, not by evaporation. Once they’re hard, they’re hard for good. That’s exactly what makes them great for a kitchen table and a headache to spot-repair. A new coat sits on top of the old one instead of melting in, so you can’t re-flow a scratch away. Modern poly is that plastic-feeling, very glossy or very even satin finish on newer furniture and floors.

How to tell which one you have

You don’t need a lab. You need a hidden spot, a couple of solvents, and a few minutes. Always test somewhere nobody will ever see: the underside of a tabletop, the back of a leg, the inside of a drawer. Never start on the top.

A few things to have on hand and a few safety notes first:

• Denatured alcohol and lacquer thinner, both from the hardware store.
• Cotton rags or cotton swabs.
• Good ventilation and no open flame. These solvents are flammable and the fumes are strong. Gloves are smart.

Now the tests, in order:

1. The denatured-alcohol test (for shellac)

Dampen a rag or swab with denatured alcohol and rub a small hidden spot for 10 to 20 seconds. If the finish gets tacky, softens, or starts to dissolve and come off on the rag, you’ve got shellac. Alcohol is shellac’s kryptonite, so a clear reaction here is about as sure as home testing gets.

2. The lacquer-thinner test (for lacquer)

If alcohol didn’t do much, try the same thing with lacquer thinner on a different hidden spot. If that softens or dissolves the finish, you’re looking at lacquer. Run the alcohol test first, because alcohol reacts to shellac but generally not to cured lacquer, and that order tells the two apart.

3. If nothing much happens, it’s probably varnish or poly

If you rub with alcohol and then with lacquer thinner and the finish just shrugs it off, staying hard and glossy, you’re almost certainly dealing with varnish or polyurethane. These cured film finishes don’t re-dissolve, and that non-reaction is your answer.

Age and type of piece back up the solvent tests:

• Pre-1920s antique with a warm amber tone: lean shellac.
• Factory dresser, cabinet, or mid-century piece: lean lacquer.
• Newer kitchen table, desk, or anything that feels like it’s under glass: lean varnish or poly.

Look and feel help too. Shellac and lacquer tend to feel thinner and more a part of the wood. Poly often has that thicker, built-up, plastic feel, with light bouncing off it in a very even, hard way.

Why any of this matters for the repair

Here’s the payoff, and it’s the whole reason I ask.

Shellac and lacquer are what we call reversible finishes. Because they re-dissolve in their own solvent, an old cloudy or scratched surface can often be amalgamated, which is a fancy way of saying we re-flow the existing finish with solvent so it melts back together and levels out. No stripping, no starting over. A lot of tired-looking antiques just need their original shellac reamalgamated and they come back to life. That’s also the family French polishing lives in, and if you’re curious, here’s what French polishing actually is in plain terms.

Varnish and polyurethane don’t play that game. You can’t melt a scratch back together, because the cured film won’t re-dissolve. When poly fails, the honest fix is usually to sand it back or strip it off and build a fresh finish. That’s more work, and it’s a big part of why a proper furniture refinishing job on a poly tabletop costs more than a touch-up on a shellac antique.

So the same scratch on two tables can mean two completely different jobs. It all rides on which finish is under there.

An honest word

I’ll level with you: identifying an old finish can be genuinely tricky. Pieces get recoated over the years, so you might have lacquer over shellac, or somebody slapped poly over an antique back in 1985 and now the tests give you mixed signals. Waxes, oils, and old repairs muddy the water too. Forty-plus years in this trade and I still run my tests carefully and sometimes get surprised.

That’s not me talking you out of trying. Do the hidden-spot test. It’s useful and it’ll often give you a clear answer. But if the piece matters to you, or the results are confusing, that’s exactly when experienced eyes and hands earn their keep. I can usually tell what’s on a piece in a minute or two, and tell you whether it’s a save-the-original job or a strip-and-refinish job before you spend a Saturday going the wrong direction.

Free assessment, no pressure

If you’ve got a piece you’re wondering about, bring it by or give me a call and we’ll figure out what’s on it and what it needs. No hard sell, just a straight answer and a free assessment.

• Call: (651) 748-9465
• Shop: 622 Como Ave #1 in Saint Paul
• Online: reach me through the contact page for a free assessment

I’ll tell you honestly whether it’s a do-it-yourself touch-up or a job for the shop, and point you the right way either way.