Article:
Your woodworking project is done. And maybe you’ve stained it too. Now you need to protect it with a topcoat. What do you choose? Maybe this information guide can help you...
from;
James King
King’s Fine Woodworking
Highlights: What are you looking for?
Fastest Drying Time:
Lacquer - 30 min
(Shellac - 1 hour
Waterborne polyurethane - 2 hrs
Standard Polyurethane - 24 hours)
Best for Crystal Clear Finish:
Lacquer
Waterborne polyurethane - close second place.
Easiest to Apply:
Wipe on polyurethane
Spray on poly from a can
Spray lacquer from a can
-All three are easy options
Easiest to Repair:
Lacquer
-Spraying on another coat partially dissolved the coat underneath, leading to perfect repairs.
Easiest to Clean Up:
Waterborne polyurethane
-Soap and warm water.
Most Durable:
Polyurethane
or Lacquer (close 2nd place)
Best for Outdoors:
Varnish
-Spar Urethane
-Detailed information on each Topcoat-
SHELLAC:
Shellac is a natural product. It is made from the dried secretions of the female Lac beetle. Once they are dried, collected, and processed, you can dissolve them in a solvent such as alcohol. And then it can be used as a finish.
Shellac dries by the evaporation of it’s solvent.
Shellac first came into widespread use for a furniture topcoat sometime in the late 1500’s. Coincidentally this was a period in history when the profession of a ‘wood finisher’ called a “Varnisher” became a distinct class of work, separate from a woodworker.
Prior to the 1960s shellac was probably the most popular form of topcoat. Shellac is also popular because you can put a a color or a tint into it. And it holds that color very well.
Shellac is very beautiful and forms a reasonably durable finish that can be high gloss in nature.
It does have drawbacks however. If you place a hot mug or a hot pan onto a shellac finish, a white ring can develop under it. It is also soluble in alcohol. So if you spill an alcoholic beverage onto it, The finish will start to dissolve. For these reasons we don’t recommend shellac for table top surfaces.
LACQUER:
Lacquer has been in use for almost 7000 years. And Chinese Lacquer-Ware has been found from the Neolithic Age. (Last part of the Stone Age) It was originally made from the sap of the “Toxicodendron vernicifluum” tree. Today it’s known as the Chinese lacquer tree
Modern lacquers however, were invented in the 1920’s and today are made via entirely synthetic means. It is extremely durable and one of the hardest of the topcoat finishes. It is stronger and better wearing than shellac and varnish. (Debatable as to whether or not it’s harder and more durable than polyurethane). Lacquer is also capable of producing an extreme high gloss finish. Lacquer is impervious to alcohol and most other common household liquids that might be spilled on it.
There are two classes of lacquer. Those that dry with solvent evaporation, (ie. the ones you buy in a big box home improvement store, such as Deft, Behlen, Rust-Oleum). And those that dry via a chemical reaction. These are called catalyzed lacquers. They are generally found at a specialty paint store, and have a very short shelf life.
Lacquer can be bought in all finishes; from matte to high gloss. It has the fastest drying time of any top coat, and thus it’s possible to achieve 3 - 4 coats in one afternoon.
Lacquer is the most forgiving of all topcoats. It’s easy to sand away a run. Or patch an area that got scuffed or simply didn’t get coated well. It is easy because application of a new coat partially re-dissolves the prior coat, and they adhere well and blend together perfectly.
Lacquer is the clearest of all topcoats. When you really want the beauty of the natural color of the wood to show through, it is ideal. However, on some species, lacquer can take away some of the depth and the 3D quality of the wood that is achieved with the amber-toned color warmth of polyurethane.
The very best way to apply lacquer is to spray it. This can be with a spray system. Or with aerosol cans. Brushing lacquer is available also. Note: brushing lacquer sprays on perfectly well! But, spray lacquer dries too fast to be brushed on.
There are drawbacks to lacquer however. Lacquer can discolor over a long time. Lacquer has a high VOC (volatile organic compound) content, which makes it dangerous to use without a respirator that has an organic vapor cartridge. A dust mask will not protect you from the vapors of lacquer.
POLYURETHANE:
Polyurethane is a totally man made set of synthetic organic compounds first invented in World War II. It is a polymer (poly = many, mer = part) made from the reaction of diisocyanate with a diol.
It is arguably the hardest & most durable of all topcoats. And in recent decades polyurethane, or poly (as I’ll call it for short), has become the go to topcoat finish for woodworkers everywhere. Nearly every finish & topcoat manufacturer has come up with a poly product for sale.
It can be bought in all finishes, from matte to gloss. And, it can be sprayed on, brushed on, or even wiped on. The wipe on is usually a thinner mix to allow for better leveling. If the Poly, is brushed on, a natural bristle brush is best to avoid bubbles that could form from a foam brush.
Polyurethane can come in two major forms. It can be oil based or it can be waterborne. The waterborne version of polyurethane is newer and has some advantages.
Waterborne polyurethane is made by combining microscopic particles of polyurethane small enough to maintain a colloidal suspension with water. It would be wrong to call this polyurethane water-based. The polyurethane’s base is still an organic solvent. It is just that this is carried by the water to make it easier in a number of ways. Waterborne polyurethane dries very quickly because as the water evaporates the microscopic particles of polyurethane are able to cure very fast.
Oil based Polyurethane has a slow dry time, usually about a day. It cures by a chemical reaction. And it must be sanded between coats to obtain a ‘tooth’ for the next coat to grab on to. The oil based poly gives a beautiful warm glow to the wood.
Waterborne poly has a quick dry time of about 2 hours. It also provides a clearer finish, it has a lower VOC, and it is easier to clean up. Just use soap and water.
VARNISH:
Varnish is often used as a generic name for topcoats. But it is actually a very specific product. This terminology difficulty is actually exacerbated by manufacturers calling their products by the wrong name for the sake of marketing. Companies in the past have freely called, shellacs, lacquers, polyurethanes, & oils all by the name Varnish.
Varnish today is usually an alkyd resin mixed with a solvent that cures to dry via a cross-linking chemical reaction triggered by oxygen molecules. It is not a lacquer, and not a shellac.
Varnish is related to polyurethane, in that Poly is a type of Varnish. Poly is harder and more rigid however, and has less oil in it. Generic Varnish, has more oil in it, and is more flexible. Chemically speaking, they are distinct and separate things.
Varnish is excellent for outdoor use, and generally impervious to saltwater, heat, cold, and UV light. Also being a cross-linked resin compound that is high in oil, it is very flexible and it can expand and contract with the temperature making it ideally suited to all weather environments.
It is quite durable. But not as durable as polyurethane. It does impart a warm glow to the wood and could certainly be used on indoor furniture. But outside of bathroom furniture, where humidity might be high, it would be uncommon to see varnished pieces inside.
Good luck on your next finishing project!
By
James King
King’s Fine Woodworking
February, 2018
SOURCES:
Polymer Science Learning Center, University of Southern Mississippi.
Journal of Chemical Education 69
Ullmann’s Encyclopedia of Industrial Chemistry
Journal of Biological Macromolecules
Germ plasm Agricultural Research Service
Rust-Oleum News Blog
Polyurethane, Lacquer, Shellac, or Varnish? What do I use? What’s the difference?
Comments (35)
This is indeed a very good article. Thank you, they are becoming rare with all the generic stuff written by people who don’t even speak English. As it is, they are also the ones that dominate the top few pages of search results. It’s disgusting so it’s very nice to find a well written informational article from someone who obviously did their homework and also has experience with the subject matter as well as a firm grasp on their native language.
With that said, I have been painting and finishing wood with stains and clear top coats going on 30 years now and these options have always been questions more than answers to me. Thankfully I started out with some old school painters back in Maine where finishes take a good beating and they showed me the ropes before I was cast into the abyss. I assume I’ve also been fortunate to not make any major mis-judgements that I know of. Or at least none that I was called on.
So now this far into my career I am working on a very small and simple project that has me stumped. I am trying to get a “piano” finish on a table I’m working on. It’s technically a coffee table as it sits between the couch and the entertainment center, close enough to the couch to be able to set a cup of coffee on. However I have made a chess/checker board, cribbage board, and Wahoo/marbles board on it that glow in the dark under UV lighting. The boards all seem fine with a lacquer over the paint however they all have hand painted textures as well as holes and lines. The area around and between them is what I am trying to get the super smooth high gloss finish on and I am having issues with the lacquer bonding and curing.
I used spray paint for the build coats, Ace Hardware Premium gloss enamel, Rust-O-Leum gloss enamel, and even Dupli-Color automotive enamels and I’ve used Rust-O-Leum standard lacquer, their acrylic Lacquer, Krylon specialty lacquer, and Dupli-Color automotive lacquer and every combination has failed.
I’m in Colorado now so I don’t think it’s an environmental issue, stuff dries really fast here. I’ve applied multiple thin coats with both the paints and clears and have tried both the recoat time frames recommended on the cans; within 10 minutes of each other or after 24 – 48 hours per the product instructions. I sand between coats with fine to super fine grits, even wet sanding with 600 to 3000 grit wet/dry papers for the final coats. I’ve tried everything per the recommendations both from the products and some advise from other sources plus a few tricks I thought I knew and every time I’ve had either one or both of the following conditions.
1,) It seems like it never dries or cures. Anything that touches it leaves an impression, even a month or more after it’s indicated curing time has passed and
2.) I noticed this while trying to fix impressions left from things being placed on it, the lacquer is not bonding to the paint.
What could I be doing wrong? Is lacquer not compatible with enamel as a suitable top coat?
I would like to seal a walking stick I have carved and stained with various colours of stains, what would you recommend to seal it and not lose the various colours?
Thanks
WOW This is exactly what I have been looking for to help my how,when,where questions
THANKS
Thank you so much. I will keep this, print it, seal it and place it in my workshop. Thank you again.
Wonderful article! I love that you included the historical background of each finish.
You answered all of my questions except one… Does waterborne poly have the same strength & durability as the oil poly?
You were so detailed with everything that I’m inclined to take your omission of that clarification to mean it wasn’t necessary because they are the same.
Great information going to get some poly😎
I have made an oak table & I am going to put 2 coats of lacquer on in but it has a lot of figure on it (cracks, one long one, knots & such) I thought of filling the cracks with 2 part epoxy & then the 2 coats of lacquer, I would love your thoughts on my plans !
Hi James,
I really enjoy the projects, the keepsake boxes in particular. Is there a brand of spray lacquer you like best? Thanks!
Drilling is a cutting process that uses a drill bit to cut a hole of circular cross-section in solid materials. The drill bit is usually a rotary cutting tool, often multi-point.
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Thank you for this post. It was exactly the information I was looking for.
Great to see such an informative content. We are good at furniture polishing services, texture painting, wood polishing services, interior painting, home painting services and much more. Contact us for a once-in-a-lifetime experience.
Absolutely one of the best articles I’ve read. We’ll done sir.
Hi James. I really want to keep color in my inlay projects. Did not know purple heart would change to brown. Very disheartening since I completed a cardinal inlay using padauk & purple heart. Hate to hear it turns brown! I want to keep green poplar green. What method do you suggest? I use hot sand blending to get shades in the pieces before they are inlaid. Heat seems to brink out the color. Will heat help keep the color? My purple iris project is destined to be brown?!! Ugh!! I used cyanoacrylate (super glue) smeared over the entire piece to lock in color. Wonder if that will last? Your thought? Thanks Thomas :)
Thankyou for the informative information it was very helpful. Just one point could a shalack first coat and a varnish top coat work on an external application .
Regards Dave.
If ur doing wood boxes and u have alot of sprinkle paints on it and u want to cover over the top of the sprinkles how would u do that
I am about to prime my kitchen worktops then creating a marble effect design on them.
I dont want to use epoxy resin as that seems difficult,can you advise what i should use for a clear heat resistant finish?
Thank you.
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Can you give me a name of varnish since it sounds like varnish may not be varnish! Thanks.
I love to build small wood projects but just stared full time any advise?
Thank you for this well researched and informative article. It has been very helpful.
Hi,
Actualy i just want to know that, Which paint sprayers better for me?
With which I can paint my house, furniture and other myself?
It would be great for me if you could tell me a little bit Please?
And How long will it last?
Hi! I’m going nuts trying to find the best top coat to protect my freshly painted (acrylic) toilet seat. It needs to be protected and stand up to cleaning and disinfecting. Lacquer would be good but it discolors over time and is dangerous to use; Shellac doesn’t hold up for table top type abuse and alcohol items etc.and Varnish can’t be used in the bathroom. So I’m thinking water based Polyurethane. Can you help me to make the right choice? I don’t want it to be too glossy. Thank You!!!
Thank you, thank you, thank you for taking the time to explain all these finishing products! I have been looking at manufacturers websites and woodworking blogs for days trying to figure out the difference between all the product lines. I read pages and pages of the fine print under the sections on “product details” and still was left without a clear understanding of how shellac differs from polyurethane or varnish or sealer. Now I get it! You rock. Thanks again.
I have been asked by my granddaughter to improve the look of a old trinket or jewel box that belonged to her other grandmother . It appears to be of Japanese origin from the pictures on it. It is generally a black and/or brown color with various painting and emblems on it and it appears to have been coated with some form of clear gloss varnish. I need to touch up some small damage at the edges. I think I can touch these up with black japan or other stain. However I am unable to determine what the coating is and what might be a safe varnish or lacquer type to use to recoat where necessary. I do not want to damage it
Finally, my projects can be finished and I will no longer be changing the subject when asked if I’ve decided on what finish I am going to use, friends and family accustomed to some nerdy indepth details and several examples that they probably dont listen to have been surprised to not get the whole knowledge base on wood finishes yet. 3 years into my hobby and have been brick walled by what the heck to use for a finish that isnt BLO, answers online haven’t been thorough enough or provide the small details or comparisons without some company that sucks pushing there product with the use of bloggers. Very grateful for this article, Especially since I now know that lacquer and varnish are my particular wants in a finish. Bookmarked this page, and hopefully still have the page bookmarked from a year ago or more that guides to what you cannot and can put onvtop of another! Or a refresher from kingsfinewoodworking would be more preferred. All I remember is that some finish,( not sure which) is by all means do not ever put over top of previously treated with boiled linseed oil. Or possibly it was never put something over top of a urethane. I wasnt to worried since I didnt know enough about the finishes I was wanting to use.
Which is best for hardwood flooring? Floor is virtually stripped down and very dry due to age, etc. I have seen some poly finishes that scratch very easily. Prefer a natural, warm, matte finish and want to avoid white ‘scratches’.
Whats your thoughts on Tru-oil for smaller projects ie: file handles ,for some reason i just like the feel of that better in my hand than laquer or shellac, what is that classified as ? Thanks …
James, thanks for the explanation. Your’s is the best concise discussion of finishes I’ve ever read. You also do a great job with the videos and it’s refreshing to see you involve your family the way you do.