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There are different types of wood finishes and most of them don’t work together so if you need to touch up a finish, how do you identify what the finish is?You can test the finish in a specific sequence. The first type of finish to test is oil. The main types of oil finishes are Boiled Linseed oil, Tung oil, and Danish oil. Any of these are compatible with each other and its easy to identify an oil finish. Put a drop of oil on the finish and let it sit for a few minutes. If it absorbs into the wood, it’s an oil finish. If it doesn’t, you have a shellac, lacquer, or poly/varnish type of finish.Another hint to identify the finish is the furniture itself. Oil finishes are more common on fine furniture and mid-century modern furniture, so consider the piece you working on. If you see the grain of the wood in the surface of the finish instead of a solid film, it’s likely an oil finish.If you’ve done the oil test on your piece, and it’s not an oil finish, the next thing to test for is a shellac finish. It’s important you test your finish in this order to determine what it is because some solvents work on multiple finishes.To test for a shellac finish, you need to use a drop of denatured alcohol. Let it sit for a a few minutes, then try to dab it up with a rag or paper towel. If the surface is sticky and mushy, it’s a shellac finish. Shellac finishes are common on antiques, so that’s a hint when you look at the furniture.The third test is to see if the finish is a lacquer. Lacquer is a common modern finish because it dries quickly, which means less chance for dust to settle on it and a higher rate of production in manufacturing. It’s not a common DIY finish because it is very toxic and usually applied with spray equipment. To identify a lacquer finish, you need to place a drop of lacquer thinner on the piece. After about 20 seconds, dab it with a rag or paper towel to see if it’s sticky. If it is, you have a lacquer finish. If it isn’t, you have a polyurethane or varnish finish.A polyurethane or varnish finish forms a protective plastic film. You need some very strong chemicals to soften the finish, which is why I suggest testing in the order of oil, then shellac, and then lacquer. By process of elimination, if nothing softens the finish, it’s polyurethane or varnish. Polyurethane and varnish will chip where the other finishes typically won’t.How do you repair these finishes? Repairing an oil finish is simple. Just apply a new coat of oil.Repairing a shellac finish is also easy, it’s just a matter of cleaning off the surface with warm water and a mild detergent such as dish soap, and then applying a new coat of shellac.To repair a lacquer finish, I clean the surface with mineral spirits to remove any oil or grease. I show how to repair a lacquer finish in a separate video – https://youtu.be/sEKQYmq0fJETo repair a polyurethane or varnish finish, the new coat of finish sits on top, so it needs something to grab on to. Sand the old finish with 400 grit sandpaper to rough up the surface and then apply a new coat. I show how to repair a polyurethane finish as part of a Windsor chair restoration in this video – https://youtu.be/92deV01eWFUOUR NEWSLETTER – Sign up at https://WoodenItBeNice.caSee the tools we use in our workshop and the tools we recommend: https://www.amazon.com/shop/homeimprovementwoodworking 🇨🇦 Canadian link – https://www.amazon.ca/shop/homeimprovementwoodworkingThis video is hosted by Scott Bennett, Owner of Wooden It Be Nice – Furniture Repair in Brooklin, Ontario, Canada. https://WoodenItBeNice.ca#woodfinish #polyurethane #shellac
Hi, Did you in the States use nitrocellulose lacquer on tables and chairs in the seventies?
That’s a question I don’t know the answer to. Sorry
@Fixing Furniture ok
Man you are knowledgeable. I am not… I have a Varnique butcher block counter top that has some minor scratches in it. Being the smart guy that I am, I decided to try and get those scratches out with Meguiras scratch remover…. it didnt work, and left somewhat “greasy, streaky pattern visible to my eye. I have tried vinegar, rubbing achy, dish soap/water, pinesol… still looks the same. Anyway to get rid of that, or is the play to leave it or sand it off and refinish? Any knowledge from anyone would be great. I should say the varnique is unique and made by John Boos.
Hi Matt. Unfortunately Megurias is meant for automotive paint, not wood. I suspect the wood has absorbed the chemicals and stained the wood. The only way to remove that is to sand it down, and depending on how deep it penetrated, it may take a lot of sanding. I hope that helps. Scott
@Fixing Furniture Thanks so much, I kind of assumed that. I’ve been putting a small amount of lemon oil on it now and again, and its seems to be helping blend it in. I appreciate you getting back to me!
Question? My wife ruined the finish on an area of our table by spilling nail polish remover on it. It removed the finish and made it sticky when we tried to clean it up. What finish would it be from that?
Nail polish remover is a very powerful solvent, therefore it could damage more than one type of finish (e.g., shellac or lacquer). It’s best to use the tests in this video to identify the finish you’re working with. Scott
I have a tabletop that is finished with dewaxed shellac, not french polish but brushed on. Over that it has 3 coats of polyurethane. I am sure of this finish because I applied it myself. The table now has 3 small circular areas where the finish was eaten away by something. I am wondering what is the best way to go about repairing those spots?
Awsome video!
Glad you enjoyed it. Scott
What can you test shellac with other than Denatured alcohol, it’s not able to be purchased in CA due to Prop 65 I’ve been told at stores here. I think I have a shellac finish, can I use shellac to test since there’s denatured alcohol in it to test?
Sorry, I don’t know the answer to that. I’ve never tried another alcohol such as vodka to see how shellac reacts. Scott
Found this site this morning by accident repairing a 1870s chair. Boy wish I found it years ago. Fantastic videos buddy, I’ll continue my viewing eagerly, thankyou.
Glad you found it helpful John. I hope our other videos are as useful for you. Cheers. Scott
Just curious to find out if you have used the 3M buffing pads to achieve the same effect as the steel wool? I have used the 0000 steel wool and 3M pads and have found the 3M pad to be less abrasive. I even used the 3M pad to buff out scratches on a table top.
Hi Terry. I use both steel wool and synthetic steel wool (scotch-bright pads). I haven’t done a direct comparison between them but now that you mention it, I do use them for different things. I use the synthetic for scrubbing a surface clean or applying wax to a finish whereas I use traditional steel wool for cleaning off finishes or in between finish coats. I don’t know if that answers your question but I hope it’s helpful. Scott
Great video!
Great video, thank you for posting – Do you have a remedy for a waterbase poly that appears slightly cloudy?
Will isopropyl alcohol work the same as denatured alcohol?
I’m not familiar with that type of alcohol, so I can’t answer that. Sorry. Scott
Just curious. I have a painted metal piece that I’m trying to determine if it is just paint or if it has a top coat. Is there any way to determine with certainty one way or another?
Did not talk about how to test the difference between varnish and polyurethane.
Thanks for your video. After watching I learned my MCM table has a shellac finish. I got denatured alcohol to remove the finish but wonder the best way to apply it and then clean the remnants. Last, I’m going to refinish with teak oil (the table is very similar to the MCM coffee table from your other video). My teak oil says to mix with teak prep. Is that necessary? I dont have that and am struggling to find. Thanks! Really appreciate your helpful vids!
Hi. To remove the old shellac, you can apply the denatured alcohol and scrub it with steel wool or synthetic steel wool. As for the Teak oil, I’m not familiar with Teak Prep so I can’t offer any advice there. Sorry. Scott
I’ve watched this video repeatedly. So useful
Glad you found it helpful. Thanks for sharing that. Scott