Which Finish? Polyurethane, Varnish, Shellac, or Lacquer?
You know you’re suppose to finish wood. But there are so many different types of wood finish! Here’s a quick summary of the different finishes, and when to use them:
|Finish Type||Durability||Dry Time||Toxicity?||When To Use|
|Oil-Based Polyurethane and Other Varnishes||Very Durable||24 hours||Toxic|| When you need a strong finish and have plenty of ventilation and time|
|Water-Based Polyurethane||Durable||2 hours||Non-toxic||Over latex paint, or when you need a durable finish quickly|
|Shellac||Moderate Durability||1 hour||Non-toxic||When you’re worried about adhesion problems, or when you need a quick finish|
|Lacquer||Durable||Toxic||When you have a high-volume low-pressure sprayer|
|Pure Oils||Poor Durability||24 hours||Non-toxic||On cutting boards|
There are some nuances to each of these, though, so lets look a little bit closer.
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Varnishes (Including Polyurethane)
Varnishes are a strong type of finish that forms a film on top of the wood. They have a long shelf life, and are readily available at big-box home improvement stores.
When you think of “wood finish,” varnishes are probably the first thing that come to mind. Oil-based polyurethane, Waterlox, Seal-A-Cell, and Arm-R-Seal are all varnishes.
Polyurethane vs. Varnish
So, lets get something out of the way. Oil-based polyurethane is a type of varnish. Specifically, it’s a brushing varnish, meaning that it’s a thicker varnish that can be brushed onto the piece.
Wiping varnishes are the other type of varnish, and they’re thinner. As you can probably predict, wiping varnishes are wiped onto a piece.
You can turn polyurethane into a wiping varnish simply by thinning it with mineral spirits.
Pros and Cons of Varnishes
Varnishes are the strongest finish on the market, hands down. If you’re looking for the most protective finish you can find, you want a varnish. That’s the primary reason to use them, because the cons are pretty harsh.
Varnishes take 24 hours to dry between coats. At first that doesn’t seem that bad. But realize that brushing varnishes require 2-3 coats, and wiping varnishes often require 4-5. If you want to use a varnish, be prepared to spend the next week finishing your piece.
Additionally, varnishes are the most toxic type of wood finish during application (for more info on wood finish toxicity and food safety, see this post.)
The fumes are dangerous, and therefore good ventilation is required when finishing pieces with varnish.
As a result of these too main drawbacks, I only break out the varnish or polyurethane when I have something that needs really strong protection, like countertops or a tabletop. Otherwise, there are faster, safer finishes to use that still provide enough protection for most purposes.
How to Apply Polyurethane/Brushing Varnish
The tricky thing about brushing varnishes is that they are thick and take a long time to dry. Because of this, every speck of dust in the room has time to settle into the finish.
An old technique for dealing with this is called “rubbing out.” I’ll describe it,
but honestly my opinion is that you’re better off thinning the last coat into a
wiping varnish to avoid the issue. Wiping varnishes are thinner and dry faster, so dust settling into the finish is less of an issue.
Step 1: Clean the Area
Since dust is such a huge factor with this method, it’s important that the room is as clean as possible. Don’t sand in the same room you apply the finish.
Step 2: Prep the Finish
Follow any directions on the can about stirring and thinning. These differ product to product, so make sure to read the instructions! Frequently the instructions may indicate to thin the first coat to act as a sealer.
Step 3: Apply
Carefully apply the finish to the piece. Be sure to brush with the grain.
Step 4: Let Dry
Brushing varnishes typically require at least 8, and usually 24
hours to dry.
Step 5: Lightly Sand
Once the finish is dry, sand lightly with 220 grit sandpaper.
Step 6: Reapply
You’ll typically require 2-3 coats.
Step 7: Rub Out
After the last coat, you’ll rub out the finish to remove any dust that got stuck during the drying process.
Take a piece of 0000 steel wool, and put a small lump of wax on it. Firmly rub the wax onto the piece, being sure to stroke with the grain. Add more wax to the steel wool as necessary.
Finally, buff the wax with a soft cloth.
Pro Tip: If you have something that requires a durable finish but you
don’t want to have to rub it out at the end, brush on the first 2-3 coats of
varnish. Sand out any brushstrokes and dust nibs.
Then wipe on the last coat of varnish. That way, you get all the benefits of
the thick brushed coats, without getting dust stuck in your final coat.
How to Apply Wiping Varnish
Dust can still get stuck in wiping varnish, but because it is thinner this is less of an issue.
Step 1: Apply Finish
Brush or pour the finish on the piece (yes, pour!) Spread it around with a brush, ensuring the entire piece is covered in a liberal coat of
varnish. If you see any dry spots, reapply the varnish.
Step 2: Wipe off Excess
After 10 minutes, wipe the excess varnish off the wood. Let dry overnight.
Step 3: Lightly Sand
Hand sand the piece with 400 grit sandpaper to remove any dust.
Step 4: Reapply
Repeat steps 1-3 to apply more coats and build the finish. You’ll typically need 4-5 coats.
Despite having a similar name to oil-based polyurethane, water-based polyurethane is an entirely different type of topcoat. The name is simply marketing to make novice wood finishers think they’re similar products.
And maybe, to the average wood finisher, they are similar products. They’re both wood finishes, right? And they do both build a film on top of the wood (which is not the case with 100% oils.)
But the chemical makeup of water-based polyurethane is entirely different (you know, water-based,) which results in different pros and cons and different rules for application.
Pros and Cons of Water-Based Polyurethane
Water-based polyurethane can be recoated in two hours. It’s non-toxic as well, so you don’t have to worry about toxic fumes. And it’s affordable and available at every home improvement store. What’s not to like?
A few things, actually. First off, in order for water-based polyurethane to be effective, it needs to be thin. Otherwise, the coats take forever to dry, and might even be tacky weeks later. (Speaking from experience here. Bad experience.)
Water-based polyurethane is also completely clear. For many people, this is a plus, but some experienced woodworkers are thrown off by the fact it doesn’t change the wood color at all. Some people miss the warmth that other finishes add to the wood.
Finally, water-based polyurethane is just not as durable as oil-based polyurethane. It’ll be fine for most projects, but for kitchen tables and countertops that’ll get heavy use, you’re better off with oil-based polyurethane.
When to Use Water Based Polyurethane
So, knowing all of that, when do I use water based polyurethane? Because it dries quickly and is non-toxic, water-based polyurethane is great for most projects that don’t require extra durability. But to be honest, I don’t actually use it that often.
Why? Because shellac, which we’ll talk about in the next session, is also all of these things.
And frankly, shellac just works. It sticks to anything. Whereas water-based polyurethane needs thin coats, and the weather has to be nice and neutral for things to come out perfectly, and you hopefully didn’t apply an oil-based stain.
So, when it comes down to it, if shellac and water-based polyurethane both work for a project, I pick shellac. And that means I rarely use water-based polyurethane.
There is one special case though, where you’ll always want to use water-based polyurethane, and that’s when you’re putting a topcoat on paint.
For the record, paint is actually a pretty durable finish on its own. However, if you want extra protection, water-based polyurethane is the way to go, because it’s totally clear and never yellows.
How to Apply Water-Based Polyurethane
So, before we start, I should mention that water-based products raise the grain of the wood, and therefore require dewhiskering. This sounds scary, but it’s pretty simple; you just have to sand after the first coat. You don’t have to sand after the remaining coats, just the first for this reason.
Step 1: Apply the First Coat
Apply the finish using a foam brush. Keep coats
as thin as possible.
Step 2: Sand
After the first coat is dry (1-2 hours), sand with 220-grit or
Step 3: Recoat
Remove any sanding dust with a damp rag, then recoat with a thin coat. Work quickly, and don’t overbrush.
Repeat if necessary; 2-3 coats are usually sufficient. Sanding is only necessary between the first and second coats.
Shellac is a resin that’s actually made by beetles. Like honey, it’s an edible product made by bugs.
Traditionally, shellac is purchased in flake form, and mixed with denatured alcohol to become wood finish. Flakes are sold at woodworking specialty stores; I don’t think I’ve ever seen them on the shelf at a big box store.
However, there are three pre-mixed shellacs that are available at home improvement stores. All of these are made by Zinsser.
I highly recommend Zinsser’s Shellac Sealcoat. It’s the only one of the three that’s wax-free, which makes it much easier to use (and more likely to adhere to your piece.)
Shellac and “Cuts”
Because shellac is traditionally sold in flake form, woodworkers have to mix the shellac before using it. The ratio of shellac to denatured alcohol is what’s referred to when we hear “1 lb cut.” The following is a table of shellac to denatured alcohol ratios, and how they’re named:
|1 lb||1 oz.||8 fluid oz.|
|2 lb||2 oz.||8 fluid oz.|
|3 lb||3 oz.||8 fluid oz.|
A 2 lb cut is typically a good starting point for finishes. You can always dilute it more if you need to. Note that this is still significantly thinner than polyurethane, so don’t be alarmed at that. It’s still the recommended starting place, though, because multiple thin coats are preferable to fewer thicker coats.
Zinsser’s Shellac Sealcoat is sold in a 2 lb cut, so you don’t need to dilute it before starting.
Pros and Cons of Shellac
Shellac is non-toxic and has a 1 hour dry time between coats. It’s durable enough for most projects, but isn’t as durable as oil-based polyurethane.
It also works. Both polyurethane types are finicky; the weathers not right, the coats are too thick, there’s oil in the wood and it doesn’t adhere, whatever. There are so many reasons polyurethane struggles to cure properly.
Dewaxed shellac, on the other hand, just works. It sticks to anything, no matter what’s in your wood, whether you used oil-based or water-based stain. It dries quickly.
Basically, if you’re using Zinsser’s Shellac Sealcoat, it’s really hard to screw up. And therefore, I love it. (Note that waxed shellacs are more difficult. I avoid them.)
There are some drawbacks to shellac, though. It dissolves in alcohol, meaning it’s a poor choice for anything that might come in contact with the substance (like a wine goblet. Don’t use shellac on a wine goblet.)
It also has a shorter shelf life than many products, which is why I recommend that when mixing flakes, you only mix what you plan to use that day. Once the shellac has gone bad, it doesn’t dry properly. Luckily, it’s pretty easy to clean up with some elbow grease and a rag dipped in denatured alcohol.
Pro Tip: If you’ve had the shellac awhile, and you’re not sure if it’s still good, test the shellac on some scrap wood first. If it dries in under an hour, you’re good to go!
Shellac is also a glossy finish, whether you’re using premixed or flakes. In order to flatten it, you need to rub the finish with some wax and steel wool, which is easy, but an annoying extra step.
How to Apply Shellac
Step 1: Mix the Shellac
I typically start with a 2 lb cut of shellac, meaning I mix 1 oz. of flakes with 8 fluid oz. of denatured alcohol. I only mix what I think I’m going to use that day, since the shelf life of Shellac is fairly short.
Zinsser’s Sealcoat comes as a two pound cut, so if that’s the product you’re working with, you shouldn’t need to do any mixing. I would stir the can before starting.
Step 2: Apply the Shellac
Brush the shellac onto the piece. If the shellac is dripping, thin it with a little more denatured alcohol.
Allow to dry for one hour.
Pro Tip: If you dedicate a brush to shellac, you don’t have to clean it
every time it’s used. Because shellac dissolves itself, if you leave the brush sitting in shellac for ten to fifteen minutes before you start finishing, it will dissolve the prior shellac, and create a soft brush ready to be used.
Step 3: Sand
Sanding isn’t actually required for adhesion, since shellac dissolves itself. However, if there are defects in the finish (like brushstrokes or dust nibs) you might want to sand between coats to eliminate these.
Lightly hand sand the shellac with 220 grit or higher sandpaper.
Step 4: Recoat
Note that shellac dissolves itself, so the second coat will not
go on as smoothly as the first. Don’t overbrush, or else you’ll risk fully
dissolving the first coat.
The more coats you apply, the longer it will take for the shellac to dry. This is normal. Do not apply the next coat until you can sand without the sandpaper sticking to the finish.
The number of coats you apply is up to you and the look you want for your piece. Anywhere from 4-10 is normal.
(Optional) Step 5: Rub Out
Shellac doesn’t contain a flattening agent, and therefore results in a very shiny finish. If you’re looking for something more matte, you can rub out the finish with a bit of wax and some steel wool.
Rubbing out the finish of shellac is pretty much the same as rubbing out the last coat of polyurethane. Simply take a piece of 0000 steel wool, and put a small lump of wax on it. Firmly rub the wax onto the piece, stroking with the grain. Add more wax to the steel wool as necessary.
When you’ve finished, buff the wax with a soft cloth.
Lacquer is a fast-drying finish that is frequently used by professional woodworkers, because it’s easy to spray and easy to fix when something goes wrong. Like shellac, lacquer dissolves itself, so sanding between coats is unnecessary.
However for the average home woodworker, lacquer is not quite as useful of a finish. It requires a high-volume low-pressure sprayer (HVLP) to apply, which is typically a $500+ investment, and therefore unattainable for most diy-ers.
Brushing lacquer is sold in many home improvement stores, however it’s difficult to brush onto pieces because it dries so quickly.
Finally, a few companies do sell lacquer in spray cans, so that people without HVLP systems can still get the benefits of lacquer. However, those cans are expensive, and therefore are really only suitable for small projects.
Pros and Cons of Lacquer
Lacquer is a favorite of professionals for very good reasons – it’s efficient to use, dries quickly, and while not quite as durable as polyurethane, it’s still a pretty durable finish.
If something goes wrong, lacquer dissolves itself, so it’s easy to fix mistakes simply by adding another coat.
But all of these great features require that the lacquer is sprayed. HVLP sprayers are expensive, and don’t make much sense to purchase if you’re only finishing one piece a week.
Lacquer in spray cans is a better option, but can get expensive if you’re finishing a large piece and need to purchase multiple cans.
Finally, like varnishes, lacquer produces toxic fumes during the dry time, making it a poor choice if you’re looking for a non-toxic finish.
How to Apply Lacquer From a Spray Can
Step 1: Prep the Piece
Like varnishes, lacquer produces toxic fumes, so be sure you’re in a space that is well ventilated.
Sand your piece with 220 grit sandpaper. Wipe the piece down before applying finish to make sure there is no remaining sawdust.
Finally, shake the can for at least 1 minute before starting.
Step 2: Apply the Lacquer
Like spray paint, you should hold the can 6-10 inches away from the piece, which is further then you think! Apply thin coats, and allow 30 minutes of dry time between coats.
The most common issue with lacquer is a white blush appearing under the finish after it dries. This happens on warm humid days, and can be prevented by warming the lacquer in a hot bath before you start.
Pure oils, like linseed oil, tung oil, walnut oil, and mineral oil have been used to finish wood for centuries. However, they are rarely used anymore, simply because modern products do a significantly better job of protecting wood.
In fact, they’re used so infrequently that if you’re interested in finishing wood with 100% oils, you’re probably going to need to purchase the oil from a woodworking specialty store.
While major home improvement stores sell things called “Tung Oil Finish” and “Walnut Oil Finish,” these aren’t actually 100% oils, but instead are varnishes that contain a small amount of oil. The only pure oil you’re likely to find at a home improvement store is linseed oil, because it has uses outside of woodworking.
Pros and Cons of Pure Oils
Pure oils do not add significant durability to wood. They’re a poor choice for any project that will be handled regularly. They also take 24 hours to dry between coats, which is a significant drawback as well.
100% oils are, however, non-toxic and food safe. While I still wouldn’t recommend them for most projects that come in contact with food (shellac is generally a better choice, see this post) cutting boards are the exception.
Most finishes protect wood by building a film on top of the wood. Pure oils work differently, and sink into the wood instead. Cutting boards are constantly hacked at by knives, which would chip off the film of traditional finishes. Those chips would land in your food, which is never great.
Therefore, pure oils are the ideal choice for cutting boards, but that’s really the only time I’d recommend them.
How to Apply Pure Oils
Step 1: Prep the Piece
Sand with 220 grit sandpaper, and wipe all remaining sawdust off of the piece.
Step 2: Apply the Oil
Pour a little oil onto the piece, and spread it around with a dry cloth. Cover the entire piece with oil, then let it sit for 15 minutes.
Step 3: Apply More Oil
After 15 minutes, check the piece for dry spots. Anywhere that’s dry, apply more oil. Continue doing this every 15 minutes until an hour has passed from the initial oil application.
Step 4: Allow the Oil to Dry
Set the piece aside, and allow the oil to dry. It should take around 24 hours, but it may take longer on particularly humid days.
Picking a Finish
So now you have all of this information, how do you decide which is the right finish for your project? Here are some questions to ask yourself:
Do I need an extra durable finish?
If you need an extra durable finish, then you should be using oil-based polyurethane. If you don’t have good ventilation, you’ll want to find a way to ventilate your space properly in order to safely apply it.
Is my space well ventilated?
If your workspace isn’t a well-ventilated area, you’ll want to use a non-toxic finish like water-based polyurethane or shellac.
Choosing between the two is a matter of personal preference. I like using shellac, simply because I’ve never had any problems with it, but water-based polyurethane is the more durable choice.
Is the wood/stain light in color?
Oil-based polyurethane and other varnishes yellow over time. Shellac and Lacquer both add some level of “warmth” to the wood when first applied, but don’t get more yellow over time. Water-based polyurethane is completely clear, and won’t add any color to your wood.
If your wood is light in color, you may want to avoid varnishes since they’ll darken the look of the piece over time. This isn’t noticeable on darker woods, but on lighter woods it can be a problem.
Still not sure?Grab this free flowchart to help you determine what finish to use on your piece!
Which Finishing Product To Use
So hopefully now you know what type of finish to choose. But what finish will you actually purchase when you get to the store? Here are some of my favorites:
Oil-Based Polyurethane/Varnish: Waterlox
I rarely use varnishes primarily because they require 24 hours of dry time between coats, and that’s only worth it to me when I have a project that requires serious durability.
I used Waterlox for the countertops, which worked well, and provided good durability for the two years I was in that house. It is more expensive than oil-based polyurethane, and I’d probably only spring for it if I needed superior durability (which is the only time I’m using varnish anyway…)
I don’t actually use water-based polyurethane that often, because when it comes down to polyurethane vs. shellac, I typically pick shellac. But sometimes I’ll do a project where I want a matte finish, and buffing out the shellac looks tricky. That’s when I’ll turn to the poly.
I do really like Varathane’s Water-Based Polyurethane, but you have to be careful to apply thin coats. Otherwise, it just stays tacky forever. Given you apply the thin coats though, it’s a great finish!
Shellac: Zinsser’s Shellac Sealcoat
I can’t rave enough about this stuff. It is literally my favorite finish, because it’s so easy to use. Open, brush onto the piece, reapply every hour or so. Nothing goes wrong; it just works.
My most recent project with shellac was this cedar chest makeover, if you’re interested in seeing it in-action.
Note that Zinsser sells two other premixed Shellac products, but they are not dewaxed. I’ve never tried them, because the dewaxed aspect is what makes the shellac able to stick to anything, which is my favorite feature.
Lacquer: Deft’s Clear Wood Finish
I used Deft’s Sprayable Lacquer a lot back when I first started doing projects with wood. It’s easy to use and difficult to screw up, but once you start making many projects, buying the cans gets expensive quickly.
I no longer keep it on hand for that reason, but it’s a great option if you’re just getting started and have a small project or two that you want to finish quickly.
Pure Oil: Rockler’s 100% Tung Oil
So, full disclosure: I’ve never actually made a cutting board before. The school I used to teach at had a solid woodworking program, and I was able to get nice, inexpensive cutting boards from them and support my school at the same time. So I did.
I’ve therefore never had the need to make a cutting board, but if I did, I’d start with Rockler’s 100% Tung Oil.
I could tell you it gets great reviews, but really, my main reason is that there’s a Rockler store 3 minutes from my house. The guys in there are really nice, and don’t give me the “dumb girl shopping for her husband” treatment, so I like supporting them.